Western Port Welcomes Waterbirds: Waterbird usage of Western Port - 2011

Western Port Welcomes Waterbirds: Waterbird Usage of Western Port B. Hansen, P. Menkhorst and R. Loyn

2011 Arthur Rylah Institute for Environmental Research Technical Report Series No. 222

Arthur Rylah Institute for Environmental Research Technical Series No. 222

Western Port Welcomes Waterbirds: waterbird usage of Western Port Birgita Hansen, Peter Menkhorst and Richard Loyn

Arthur Rylah Institute for Environmental Research 123 Brown Street, Heidelberg, Victoria 3084

June 2011

In partnership with:

Arthur Rylah Institute for Environmental Research Department of Sustainability and Environment Heidelberg, Victoria

Report produced by:

Arthur Rylah Institute for Environmental Research Department of Sustainability and Environment PO Box 137 Heidelberg, Victoria 3084 Phone (03) 9450 8600 Website: www.dse.vic.gov.au/ari

Š State of Victoria, Department of Sustainability and Environment 2011 This publication is copyright. Apart from fair dealing for the purposes of private study, research, criticism or review as permitted under the Copyright Act 1968, no part may be reproduced, copied, transmitted in any form or by any means (electronic, mechanical or graphic) without the prior written permission of the State of Victoria, Department of Sustainability and Environment. All requests and enquiries should be directed to the Customer Service Centre, 136 186 or email customer.service@dse.vic.gov.au Citation: Hansen, B., Menkhorst, P. and Loyn, R. (2011) Western Port Welcomes Waterbirds: waterbird usage of Western Port. Arthur Rylah Institute for Environmental Research Technical Report Series No. 222. Department of Sustainability and Environment, Heidelberg, Victoria ISSN 1835-3827 (print) ISSN 1835-3835 (online) ISBN 978-1-74287-182-0 (print) ISBN 978-1-74287-183-7 (online) Disclaimer: This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.

Front cover photo: An example of an unmodified coastal environment at Spit Point, French Island: a high-tide waterbird roosting site on the exposed sand spit with mangroves, saltmarsh, Melaleuca scrub and eucalypt woodland behind. (Photographer Peter Menkhorst).

Authorised by: Victorian Government, Melbourne Printed by: NMIT Printroom, 77–91 St Georges Road, Preston 3072

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Contents List of tables and figures...................................................................................................................v List of Acronyms ............................................................................................................................. vi Acknowledgements......................................................................................................................... vii Summary............................................................................................................................................1 1 1.1

Introduction.............................................................................................................................3 Background to project...............................................................................................................3

1.2

Waterbirds in Western Port.......................................................................................................5

1.3

1.2.1

Information on waterbird breeding in Western Port..................................................8

1.2.2

Broad-scale influences on waterbird numbers...........................................................9

1.2.3

Local influences on waterbird numbers.....................................................................9

Current land uses and threats to waterbird populations ............................................................9 1.3.1

Disturbance..............................................................................................................11

1.3.2

Climate change risk assessment ..............................................................................12

1.4

Project objectives ....................................................................................................................13

2 2.1

Methods..................................................................................................................................14 Site description .......................................................................................................................14

2.2

Data acquisition ......................................................................................................................14 2.2.1

Waterbird monitoring data ......................................................................................15

2.2.2

Spatial data ..............................................................................................................15

2.2.3

Other data ................................................................................................................15

2.3

Field survey.............................................................................................................................15

2.4

Data analysis ...........................................................................................................................16 2.4.1

Preliminary trend analyses ......................................................................................16

2.4.2

Modelling of trends .................................................................................................16

2.4.3

Analyses of site importance.....................................................................................17

2.5

Movements of banded birds....................................................................................................18

2.6

Mapping ..................................................................................................................................18 2.6.1

Existing mapping information.................................................................................18

2.6.2

Construction of waterbird maps ..............................................................................19

2.7

Assessment of climate change inundation risk .......................................................................19

2.8

Community engagement .........................................................................................................19

3 3.1

Results ....................................................................................................................................20 Opportunistic field surveys .....................................................................................................20 3.1.1

Observations of breeding.........................................................................................22

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3.2

Population trends and responses to explanatory variables......................................................22 3.2.1

Modelling ................................................................................................................23

3.2.2

General species by site trends..................................................................................26

3.3

Sites of importance .................................................................................................................26

3.4

Movements of banded birds....................................................................................................32

3.5

Mapping ..................................................................................................................................34

3.6

Climate change risk.................................................................................................................38

3.7

Threats at key sites..................................................................................................................40

4 4.1

Discussion ..............................................................................................................................43 What influences waterbird population dynamics in Western Port? ........................................43 4.1.1

Changes in local fisheries........................................................................................43

4.1.2

Reduced rainfall and water availability...................................................................45

4.2

What are the causes of waterbird declines? ............................................................................46

4.3

Important areas for waterbirds in Western Port ......................................................................47 4.3.1

Habitat use by shorebird species .............................................................................47

4.3.2

Habitat use by other waterbird species ....................................................................50

4.3.3

Breeding sites ..........................................................................................................51

4.4

What threats are operating at key sites?..................................................................................52

4.5

Climate change risks ...............................................................................................................53

4.6

Management recommendations ..............................................................................................55

4.7

4.6.1

Key roosting and foraging sites ...............................................................................55

4.6.2

Ecological monitoring and evaluation.....................................................................55

4.6.3

Communication and messaging...............................................................................56

Concluding remarks ................................................................................................................57

References ........................................................................................................................................58 Appendix 1. Details of species trends from 1973–present at each count site in Western Port.64 Appendix 2. New mapping of individual high-tide roost sites in Western Port. .......................67

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List of tables and figures List of tables

Table 1. Waterbird guilds investigated in this study. ..........................................................................6 Table 2. Population trends in waterbird species from 1973–2009. ...................................................25 Table 3. Summary of modelling results. ...........................................................................................26 Table 4. Mean abundance and number of species per count (1997–2009), total count effort (1973– 2009), number of years the total abundance exceeded the threshold for ‘high importance’ and relative ranks for each major waterbird site. ....................................................................29 Table 5. Details of captures and recaptures of banded shorebirds used to infer movement patterns.32 Table 6. Matrix showing details of movements by individual birds over different time scales........33 Table 7. Summary of inundation risk for each mapped high-tide roost site, derived from GIS spatial analysis of LiDAR Digital Elevation Models (<2.5 m) and high-tide polygon shapefiles. ...............................................................................................................................39 Table 8. A list of main threats operating at key waterbird sites in Western Port..............................41 List of figures

Figure 1. Map of Western Port............................................................................................................5 Figure 2. The East Asian–Australasian Flyway. .................................................................................7 Figure 3. Map of Western Port showing key waterbird sites (green stars). ......................................14 Figure 4. Aerial imagery of Western Port showing opportunistic survey coverage. ........................21 Figure 5. Trends in all waterbirds combined between 1974 and 2009..............................................23 Figure 6. The Australian White Ibis commonly feeds on the tidal mud flats of Western Port. ........24 Figure 7. Grey-tailed Tattlers roosting at high tide...........................................................................24 Figure 8. Maximum annual counts of Australasian (a) and Holarctic (b) shorebirds at Bunyip River and Yallock Creek between 1997 and 2009............................................................................27 Figure 9. Total abundance plotted against number of species for each site from 1973 and 2009.....28 Figure 10. Distribution of sites in Western Port and their relative ‘importance’, based upon rankings of total abundance and number of species. ..............................................................30 Figure 11. Aerial view of Barrallier Island and associated mudflats (foreground)...........................30 Figure 12. Examples of high-tide roosting sites for shorebirds in Western Port, 9 December 2009.31 Figure 13. Movements by small shorebirds detected using recaptures of banded birds. ..................33 Figure 14. Red-necked Stint, the most common shorebird in Western Port. ....................................34 Figure 15a. New mapping of waterbird habitat use in Western Port: high-tide sites........................35 Figure 15b. New mapping of waterbird habitat use in Western Port: important foraging areas.......36 Figure 16. New mapping showing all available habitat for waterbird roosting, foraging or breeding. .................................................................................................................................37 Figure 17. Importance of each site for shorebirds (Australasian and Holarctic)...............................38 Figure 18. Aerial image of Western Port showing the current distribution of seagrass beds (green shading) with respect to high-tide roosts (in red). ..................................................................50

v

List of Acronyms AHD

Australian Height Datum

AIC

Akaike Information Criterion

ARI

Arthur Rylah Institute for Environmental Research

AWSG

Australasian Wader Studies Group

BA

Birds Australia

BOCA

Bird Observation & Conservation Australia

CAMBA

China–Australia Migratory Bird Agreement

CCB

Central Coastal Board

DEM

Digital Elevation Model

DPI

Department of Primary Industries

DSE

Department of Environment and Sustainability

FV

Fisheries Victoria

GDA94

Geocentric Datum of Australia 1994

GIS

Geographical Information System

JAMBA

Japan–Australia Migratory Bird Agreement

NWFI

North-west French Island

PINP

Phillip Island Nature Parks

PV

Parks Victoria

ROKAMBA Republic of Korea–Australia Migratory Bird Agreement SII

Spatial Information Infrastructure

SOI

Southern Oscillation Index

VWSG

Victorian Wader Study Group

WP

Western Port

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Acknowledgements The Western Port Welcomes Waterbirds project was supported by the Central Coastal Board (CCB), through funding from the Australian Governmentâ&#x20AC;&#x2122;s Caring for our Country. This study is one component of that project initiated by the CCB after their successful bid for funding. The Executive Officer of CCB, Annette Hatten, and her staff are thanked for their exemplary administrative support and project supervision. The project was overseen by a Steering Committee comprising Don Saunders (Bird Observation & Conservation Australia), Dr Rosalind Jessop (Central Coastal Board), Phil Fowler (Parks Victoria), Mark Smith (Port Phillip and Westernport Catchment management Authority) and Peter Menkhorst (Arthur Rylah Institute for Environmental Research). Dr Catharina Greve (CCB) provided much needed help with GIS and map preparation. Final versions of print maps were produced under contract by Richard Stewart and Peter Debicki, Spatial Information Infrastructure (SII), Department of Sustainability and Environment (DSE).

Data utilised in this study came from multiple sources and was invariably provided freely and in a spirit of collaboration, for which we are extremely grateful. The study would not have been possible without access to the extraordinary waterbird database assembled by the BOCA Western Port Survey over the last 37 years. We thank Dr Xenia Dennett and Laurie Living for provision of the data in a format suitable for analysis. Similarly, the Victorian Wader Study Group (VWSG) made available its data from shorebird banding in Western Port since the late 1970s. Birds Australia provided access to the resources of the Shorebirds 2020 project and to GIS shapefiles relating to earlier attempts to map shorebird habitat in Western Port. We thank Ash Herrod, Rob Clemens and Golo Maurer for their assistance. The Future Coasts Program of DSE provided digital elevation data for Western Port. Paula Baker at Fisheries Victoria (DPI) provided data on reported fish catch in Western Port from 1978 to 2009.

Dave Stephenson (Parks Victoria, French Island) kindly provided information on breeding of Cape Barren Geese and observations of other waterbirds, which he made on French Island prior to and during the study period.

Field and logistical assistance was provided by Parks Victoria French Island staff, particularly Mick Douglas, Dave Stephenson, Ben Fox and Scott Coutts. David Middleton kindly flew BH and PM on a reconnaissance flight over Western Port to help gain an appreciation of the known and potential waterbird habitats. Similarly, Pelican Expeditions and Parks Victoria provided a berth for us aboard SV Pelican when she was operating in Western Port for the Two Bays Project, allowing us to obtain a greater appreciation of intertidal and shoreline habitats.

Huge numbers of volunteers have been involved either directly or peripherally in this project. The most prominent of these are the BOCA Western Port waterbird counters. These tireless members are too numerous to name here individually and so we collectively thank these people, plus members of the VWSG and BA for their efforts over the years that have helped make this project possible.

We would also like to thank our ARI colleagues for their support and/or assistance along the way: Kasey Stamation, John Mackenzie, Bruce McBeath, Steve Sinclair, Josephine MacHunter, Michael Johnston, Eddie Buzinskas, and Fiona Warry. Michael Scroggie, Andrew Gormley and Dave Ramsey all provided invaluable statistical advice.

Improvements to drafts of this report were kindly suggested by Annette Hatten, Roz Jessop, Don Saunders, Catharina Greve, Clive Minton (VWSG), Phoebe Macak (ARI) and Danny Rogers (ARI).

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Western Port Welcomes Waterbirds: Waterbird usage of Western Port

Summary Western Port Welcomes Waterbirds is a Caring for Our Country funded project aimed at improving our understanding of waterbird population dynamics and habitat use in Western Port, central southern Victoria. The primary focus of the study is intertidal and coastal habitats occurring within the Western Port Ramsar boundary, although hinterland swamps and wetlands of French Island are also included where appropriate. Data relating to waterbird usage from the early 1970s onward were collated from bird study groups and supplemented with opportunistic field surveys. The combined dataset was examined to identify trends in species abundance, important high-tide roosting sites and low-tide foraging areas. Movement patterns of two small shorebird species, Red-necked Stint and Curlew Sandpiper, were also explored. Species were assigned to foraging guilds to look for broad trends and then considered individually as appropriate. Roosting sites were ranked according to their importance for waterbirds generally, and for shorebirds in particular, using a quantitative ranking system. Threats potentially impacting on important roosting and foraging sites were identified and general management recommendations are included.

Over the 37 years for which data were available there has been a general decline in abundance of waterbirds across Western Port, with only one species, the Australian Pied Oystercatcher, significantly increasing in number. In contrast, 16 species have significantly declined throughout the study period. Reasons for these declines could not be defined with confidence and are probably mostly extrinsic. However, the size of commercial fish catches co-varied significantly with counts of a number of species, including three species of cormorant, four Holarctic shorebirds, one tern, one spoonbill and one heron. This suggests that declines in fish populations, possibly related to declines in cover of sea grass, have negatively affected the population numbers of fish-eating birds. Rainfall in western Victoria and Darling River streamflow co-varied with two species, Australian Shelduck and Caspian Tern, reflecting the capacity of waterbirds to move to distant waterbodies that provide alternative habitat.

Recapture data from banded birds were used to investigate movement patterns between high-tide roosts within Western Port, resulting in the recognition that three key sites in the north of the bay—Bunyip River–Yallock Creek, Stockyard Point and Barrallier Island— may in effect be one roost system. The most important high-tide areas for waterbirds more generally were found to be Pioneer Bay, Barrallier Island, Bunyip River mouth–Yallock Creek mouth, and Reef Island–Bass Bay. All of the key high-tide roosts are potentially threatened by the predicted rise in sea level of 0.8 metres by 2100 forecast in the Victorian Coastal Strategy. This is especially true for those located on small low-lying islands, and those where the immediate hinterland has been cut off by the construction of levees or other impediments to the movement of water and sediment. The latter scenario may potentially be mitigated by the construction of artificial roosting habitat and strategic land acquisition. However, the difficulty in predicting changes to current sedimentation patterns under various climate change-related sea level rise scenarios make prediction of impacts on hightide roosts highly uncertain.

Apart from changes to sea level, the major threats to waterbirds in Western Port are disturbance by people and their companion animals, both from the land and from vessels, predation by introduced animals such as foxes and cats, and habitat modification through vegetation succession, erosion, storm surges and, potentially, changes to grazing regimes.

An important output of the Western Port Welcomes Waterbirds project was the production of maps showing the distribution of important waterbird habitat. Consequently, new and more detailed mapping (than that previously undertaken by Birds Australia) is provided of high-tide roosting sites and intertidal foraging areas. These maps will be available at a later date on the internet.

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Western Port Welcomes Waterbirds: Waterbird usage of Western Port

The major management recommendation arising from this study is to improve understanding amongst land managers and the public about important sites for waterbirds in Western Port. This includes changing behaviours and instigating management aimed at maintaining habitat quality at those sites. One immediate means of effecting this is the installation of signs strategically placed to reach most users of the bay and the smaller number of people who venture close to the important sites. Wider dissemination of waterbird information to the general public and particular bay user groups is also needed to help them understand how to enjoy what the bay has to offer with minimal damage to the shorebirds and their environment.

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Western Port Welcomes Waterbirds: Waterbird usage of Western Port

1 Introduction Western Port is located approximately 65 km south-east of Melbourne and is the second largest tidal embayment opening to Bass Strait in Victoria. The Western Port embayment is 680 km2 in area with 263 km of coastline (Blake and Ball 2001), and encompasses four local government jurisdictions: Mornington Peninsula Shire Council, City of Casey, Shire of Cardinia and Bass Coast Shire. It contains two large islands, French and Phillip, plus numerous small (usually rocky) islets. The tidal range in Western Port is the largest anywhere in Victoria – up to three metres (http://www.exploreunderwatervictoria.org.au/north-arm-westernport, accessed 26 May 2011).

Western Port is characterised by extensive intertidal mudflats with substantial cover of seagrass, deep channels in the west and north, fringing saltmarsh, mangrove and swamp paperbark vegetation communities (especially on French Island) and numerous freshwater and saline swamps. The catchment of Western Port supports a human population of 225 000 (Kellogg Brown and Root in prep.).

1.1 Background to project Western Port has considerable biodiversity value (Andrew et al. 1984) and is one of the three most important sites in Victoria for waterbirds, regularly supporting over 10,000 shorebirds from 37 species and over 10,000 waterfowl (Watkins 1993, Loyn et al. 2001, BOCA 2003). Prior to and during the 1980s it regularly supported over 5% of the known Victorian population of eight species of migratory shorebird (Lane 1987). It has long been recognised as a wetland of international significance for migratory shorebirds and this is reflected in its listing under the Ramsar Convention (1971), and its inclusion in the East Asian–Australasian Shorebird Site Network.

In 2010, Western Port was also listed as an Important Bird Area (BirdLife International) on the basis that it regularly supports more than 1% of the global population of Eastern Curlew, Rednecked Stint and Australian Pied Oystercatcher, plus declining numbers of two threatened species, Fairy Tern and Orange-bellied Parrot (http://www.birdata.com.au/iba.vm, accessed 26 May 2011).

However, as Western Port is also widely used for human recreation and industry, considerable pressure is placed on the biodiversity resources and ecological functioning of the bay. This pressure is anticipated to increase with projected human population increases, planned industrial development and projected sea level rises.

Accordingly, in July 2008, the Central Coastal Board and Arthur Rylah Institute (ARI) of Department of Sustainability and Environment, successfully applied to the Commonwealth Government’s Caring for our Country Grant Scheme for funding to undertake a two-year project titled Western Port Welcomes Waterbirds. The overall aim of this project was to improve our understanding of waterbirds in Western Port through accumulation and updating of information relating to waterbirds and their habitats. This report is one output of that project.

The study area is the Western Port Ramsar site, French Island and the north-eastern region of Phillip Island (Rhyll Inlet to Newhaven) (Figure 1). The southern boundary of the Ramsar site extends from the Phillip Island bridge around the north coast of the island to the eastern end of Silverleaves Estate (near Cowes) and then in a straight line westwards to Point Leo on the western shore of Western Port.

Shorebirds and other waterbirds in Western Port have been monitored by volunteers since 1973 and every year since then (Loyn 1978, BOCA 2003). Data from these counts suggest long-term declines in the abundance of some species (BOCA 2003), although no formal testing of trends has been undertaken in recent years. Declines may be caused by a range of impacts and landscape modifications, including disturbance, loss or degradation of habitat, and food web changes.

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Western Port Welcomes Waterbirds: Waterbird usage of Western Port

A variety of threats are known to affect waterbirds. Waterbirds are sensitive to disturbance by people and their companion animals, and public access to important roosting and foraging sites may result in unwitting disturbance to birds using those areas. Loss and degradation of shoreline vegetation through inappropriate land use practices results in loss of both roosting and breeding habitat. Erosion of foreshore substrate reduces available feeding and roosting habitat. Sediment exports from the catchment have potentially contributed to past seagrass declines (Blake and Ball 2001, Wallbrink et al. 2003, Shepherd et al. 2009), which have affected invertebrate and fish communities and thus, the birds that rely on those marine fauna for prey.

Conservation of waterbird habitat and minimisation of disturbance is impeded by a lack of detailed knowledge amongst land managers and the public about the location and significance of waterbird roosting and foraging habitat. In addition, changes to the coastline through projected sea level rises associated with climate change are predicted to impact waterbirds through loss of habitat (Austin and Rehfisch 2003).

In 1975, the Victorian Ministry for Conservation coordinated a comprehensive environmental assessment of Western Port and its surrounding hinterland. The report (Shapiro 1975) highlighted a range of past and present management considerations for the region, which included an investigation of important sites for waterbirds in Western Port. Shapiro (1975) states ‘Future work should concentrate on the ecology of the birds so that their role in the ecosystem can be understood and modelled, and the effects of any development predicted more accurately’. Since the production of that report, a large body of information about waterbirds (particularly shorebirds) in Western Port has been accumulated, including count data and mark–recapture studies, both primarily organised and conducted by volunteers. In order to improve the focus of management effort and halt unwitting degradation of waterbird habitat, more comprehensive analyses of these data are needed to explore both past population trends and predicted population trajectories in relation to changes in the bay.

Waterbirds are an important component of any wetland or estuarine system because they rely upon the resources in these environments, and changes affecting the quality and availability of these resources will also affect the birds. In Western Port, the presence of important estuarine and marine resources like fish, seagrass, saltmarsh and mangrove communities, and near-coastal wetlands, relate to the diversity of bird populations occurring therein. Waterbirds, by virtue of their visibility and conspicuousness, can provide useful indicators of the ‘health’ of these resources.

Therefore, it is important to understand what drives trends in waterbird populations over time, in order to predict trajectories of change for these species.

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Western Port Welcomes Waterbirds: Waterbird usage of Western Port

Figure 1. Map of Western Port.

1.2 Waterbirds in Western Port At least 253 bird species have been recorded in Western Port, including 102 species of waterbird and 151 other species, including bush birds (passerines), raptors, cockatoos and parrots, pigeons, cuckoos and quail (BOCA 2003). For the purposes of this study the term ‘waterbird’ refers to any bird species which depends upon aquatic (freshwater, estuarine or marine) resources for some or all of its life history cycle. Waterbirds can be categorised into a number of groups or ‘guilds’ which typically represent their dominant feeding (foraging) mode and thus, their habitat requirements.

In Western Port, 11 guilds of waterbirds are recognised (BOCA 2003) and regularly monitored.

Nine are considered here (Table 1) by virtue of their strong association with the intertidal environments that are the focus of this study. Guilds not included in this study are geese and seabirds (shearwaters, penguins and gannets). Rails are subject to only superficial investigation owing to their cryptic habits and predominant association with non-tidal freshwater and estuarine waterbodies.

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Western Port Welcomes Waterbirds: Waterbird usage of Western Port

Table 1. Waterbird guilds investigated in this study.

These definitions are derived from BOCA treatment of species as recorded in their databases and publications (Loyn et al. 2002). These definitions are used throughout this study.

Waterbird guild

Description

Typical species

Australasian shorebirds (waders)

Includes all resident shorebird species and the transTasman migratory species, Double-banded Plover

plovers, lapwings, avocets, stilts and oystercatchers

Ducks

Includes all dabbling, diving and surface feeding waterfowl, excluding geese and swans

Chestnut and Grey Teal, Australian Shelduck, Pacific Black Duck, Musk Duck

Fishers

All fish-eating freshwater, estuarine and marine species, excluding seabirds

cormorants, pelicans, terns

Grebes

Small surface-diving birds which eat mostly invertebrates and small fish

Australasian, Hoaryheaded and Great Crested Grebes

Gulls

Scavenging species that are often thought of as members of the seabird guild, but unlike seabirds are regular users of estuarine environments

Pacific and Silver Gulls

Large Wading Birds

All long-legged, large-bodied wading birds that are not annual transequatorial migrants

herons, ibis, spoonbills and egrets

Holarctic* shorebirds (waders)

Transequatorial migrants that typically breed in the Arctic (above 60o latitude) and spend the nonbreeding period during the austral summer in southerly latitudes

sandpipers, curlews, godwits and plovers

Rails

Freshwater and estuarine edge-feeders, mostly skulk in dense vegetation but coots feed from open fresh water

coots and swamphens

Swans

This guild contains the only herbivore regularly occurring in intertidal areas and on marine waters in Western Port

Black Swan

* Referred to in earlier publications (e.g. BOCA 2003) as Palaearctic. Holarctic includes both the Palaearctic and Nearctic zoogeographical regions in the northern hemisphere.

Waterbirds use a variety of habitats in Western Port but the most important are intertidal and wetland habitats, and their associated riparian vegetation communities. Western Port contains extensive intertidal mudflats, approximately 270 km2 in area (just over a third of the total embayment area), about 57% of which is covered with seagrass beds of varying species and density (Blake and Ball 2001).

Western Port also contains extensive and highly diverse fringing saltmarsh habitat accompanied in many locations by mangrove Avicennia marina (Ross 2000, Rogers et al. 2005). These saltmarsh and mangrove communities are the most productive anywhere along the Victorian coastline and contribute significant levels of detritus to Western Port estuarine and marine environments (Shapiro 1975, Rogers et al. 2005). Since the draining of the Koo Wee Rup swamp in the early 20th century (Shapiro 1975), most near-coastal freshwater wetland habitat exists either as artificial impoundments and water treatment plants on the mainland, or as shallow ephemeral swamps on the relatively un-developed French Island (Quinn and Lacey 1999, Biodiversity Interactive Maps, DSE).

Collectively, waterbirds use Western Port habitats for all stages of their life cycle. The most notable and obvious of these uses is for foraging and roosting (resting). Sandy spits and islands, rocky points, exposed mud banks, mangroves, the edges of streams and other wetlands and artificial structures all provide important roosting sites. Channels, saltmarsh, brine- and freshwater-swamps, and intertidal mudflats (with or without seagrass) provide a wide range of foraging habitat. However, of all waterbird guilds, tidal flats and high-tide roosts are most important to shorebirds (also called waders).

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Western Port Welcomes Waterbirds: Waterbird usage of Western Port

Shorebirds are a specialised group of birds adapted to foraging on muddy and sandy aquatic and semi-aquatic substrates. They often have elongated bills for probing sediments for invertebrate prey, long legs for wading in shallow water and fine pointed wings adapted for long-distance flight (Lane 1987, Hayman et al. 1995, Geering et al. 2007). Many shorebird species breed in the northern hemisphere during the brief Arctic summer, and migrate to the southern hemisphere, including to Australia, after breeding has been completed. These transequatorial migratory shorebirds begin arriving in southern Australia in late August and have departed again by April, although immature birds not yet able to breed often remain all year.

Transequatorial migratory shorebirds transit through southern and eastern Asia on their way to and from the breeding grounds (Geering et al. 2007). Here they stop over (stage) on intertidal mudflats to supplement their dwindling fat reserves. Highly productive staging sites are most critical on northward migration when birds have a strict timetable for arrival at their breeding grounds (Geering et al. 2007). Similarly, these staging sites are also used on southward migration to their non-breeding grounds, although with less strict timelines for arrival. These migrations differ in distance depending on the species, but can be up to 12 000 km for many species (Minton et al.

2011). Some species are known to make single flights of over 11 500 km on their northward migration (Bar-tailed Godwit; Gill et al. 2009). Figure 2 shows shorebird migratory pathways to and from the Australian region (collectively termed the East Asianâ&#x20AC;&#x201C;Australasian Flyway). As the migration endpoint of many species, Western Port is critical habitat for birds during their nonbreeding season.

Figure 2. The East Asianâ&#x20AC;&#x201C;Australasian Flyway.

Some sites of importance to shorebirds during their non-breeding season and for staging on migration are shown with numbers. Source: Australasian Wader Studies Group.

In contrast to transequatorial migrant species, most of the Australasian shorebird species can be found in Western Port at any time of year, though numbers vary seasonally as they move between breeding and non-breeding habitat. There are two exceptions, which are only found in Western

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Western Port Welcomes Waterbirds: Waterbird usage of Western Port

Port in specific seasons as non-breeding visitors from elsewhere. One is the Double-banded Plover, which breeds in New Zealand in springâ&#x20AC;&#x201C;summer and migrates to southern Australia for the winter: it can be found in Western Port from February to September. The other is the Red-necked Avocet, which breeds mainly in inland Australia, and occurs in Western Port in late winter and spring. Pioneer Bay, in the east part of Western Port, is the most south-easterly location for flocking avocets, and they regularly occur in the intertidal zone there, which is unusual for this species (C. Minton pers. comm.).

The remaining locally breeding shorebird species use a wide range of habitats for foraging and nesting. Many of them feed extensively from intertidal mudflats (along with the migratory species) but they cannot nest below the tide line so they need to use a range of alternative local habitats for nesting, and often for foraging as well. For example, Masked Lapwings often feed and nest in grassland near freshwater wetlands, though flocks also feed from mudflats outside the breeding season. Black-winged Stilts feed and nest in freshwater swamps, and numbers fluctuate with availability of water locally and in inland Australia (BOCA 2003). Australian Pied Oystercatchers feed extensively from sandy beaches as well as mudflats, especially on fox-free French Island where many nest on beaches or saltmarsh above the tide line. Australian Pied Oystercatchers are strictly coastal and rely heavily on the mudflats, saltmarsh, sandy shores and other high-tide roosts.

Sooty Oystercatchers are most commonly found on rocky platforms and preferentially forage in this habitat (Considine 1979).

1.2.1

Information on waterbird breeding in Western Port

There are a number of sites within Western Port known to be important for breeding waterbirds.

These have been identified and described elsewhere (Dann 1981, Quinn and Lacey 1999, PPK Environment and Infrastructure 2000, BOCA 2003) and only an overview is provided here.

French Island is by far the most important area for breeding waterbirds, but even this site has experienced marked fluctuations over time in breeding colonies and individually nesting birds (Quinn and Lacey 1999). This is because many birds are reliant on wetland habitat for successful breeding, and the majority of these habitats have become unavailable during periods of extended drought due to drying. Several sites on French Island, which used to be very important for colonies of some species have been deserted in recent years, for example, the pelican colonies at the Duck Splash, Palmer Point and Red Bill Creek, and the spoonbill, ibis and cormorant colonies at the Duck Splash, Clump Lagoon, and the Heifer swamps (Quinn and Lacey 1999, PPK Environment and Infrastructure 2000). Other past breeding records include Blue-billed Duck, Pacific Black Duck, Chestnut Teal, Purple Swamphen and Dusky Moorhen at the Heifer swamps (Quinn and Lacey 1999), and Nankeen Night Heron, Purple Swamphen and Pacific Black Duck at Bullock and Decoy swamps.

On French Island Australian Pied Oystercatcher successfully breed, which is thought to be related to the lack of foxes (Campbell 1993). On Phillip Island, Red-capped Plover and Hooded Plover breed on the sandy ocean beaches. Rhyll Swamp on Phillip Island and Coolart Wetlands on the mainland are intermittently important for breeding Little Pied Cormorants, spoonbills and ibis are and (BOCA 2003). Black Swans and Australian Shelduck breed in freshwater and saltmarsh swamps at many locations on French Island (Quinn and Lacey 1999, PPK Environment and Infrastructure 2000).

Tortoise Head on French Island, has always been an important site for breeding Short-tailed Shearwaters (Quinn and Lacey 1999), as is Cape Woolamai on Phillip Island. Breeding colonies of Little Penguin and Crested Tern also occur on Phillip Island. Little Penguin has been recorded breeding on Barrallier Island in recent years. Rams Island is used regularly as a breeding site by Fairy and Caspian Terns, and these two species have been occasionally recorded as breeding at Tortoise Head (BOCA 2003). Hooded Plover, Red-capped Plover and Australian Pied

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Oystercatcher also breed on Observation Point and Silverleaves Beach. A large colony of ibis both Australian and Straw-necked breed at Rhyll Swamp â&#x20AC;&#x201C; up to 10,000 birds have been counted flying into the wetland during the breeding season. Rhyll Swamp is also a breeding site for Royal Spoonbill and Pied Cormorant (17 pairs in 2011: PINP unpubl. data).

Mainland breeding sites are few and far between. Red-capped Plovers have bred previously on Long Island, Settlement Rd, Stockyard Point and The Gurdies (Rogers and Eades 1997), and both Red-capped and Hooded Plovers have bred at Sandy Point (PPK Environment and Infrastructure 2000). Coolart Wetlands is an important site for colonially breeding species like Little Pied Cormorants, Royal Spoonbill and Australian White Ibis (Lowe 1981, B. Thomas unpubl. data).

Australian White Ibis breeding pairs were plentiful in early years but the colony appeared to collapse during the mid-nineties, probably due in part to drought conditions and exacerbated by predation pressure from birds of prey and ravens (B. Thomas unpubl. data). The possibility of increased predation by cats and foxes on mainland birds, as a function of increased human population pressure and development, cannot be discarded.

1.2.2

Broad-scale influences on waterbird numbers

Australian waterbirds are highly mobile and respond to changes in climate and their environment at a continental and even global scale (Kingsford and Norman 2002, Chambers and Loyn 2006). It is beyond the scope of this report to deal with all possible variables in any detail, however, previous work in Western Port has shown the influence of continental rainfall patterns on local numbers of several species. Some waterbirds become scarce in Western Port during years of widespread flooding in inland Australia, and very numerous in years following such flood events as inland waters recede (Dann et al. 1994, Loyn et al. 1994, Chambers and Loyn 2006, Norman and Chambers 2010). Furthermore, wetland water extraction in inland eastern Australia has been linked to declines in some resident and migratory shorebird species (Nebel et al. 2008). It is clear that inland water availability is important to populations of some waterbird species and needs to be considered in long-term habitat management.

Populations of migratory shorebirds are also known to respond to anthropogenic factors in regions away from Western Port and possibility outside of Australia. Numerous species that utilise important staging sites in Asia, particularly the Yellow Sea, have been declining at an alarming rate in recent years. At least two species, Red Knot and Great Knot, are known to be declining due to loss of intertidal habitats at their staging sites, and more are suspected to be declining for similar reasons (Inglis and Rogers 2010, Rogers et al. 2010b, Lewis and Russell-French 2011). Any actions to protect migratory species in Australia need to be coupled with similar actions elsewhere in the flyway.

1.2.3

Local influences on waterbird numbers

Local factors that might influence waterbird numbers are less straightforward and quantifiable.

Local climate patterns may influence local breeding success, which has occurred recently with the reduced rainfall and subsequent drying of swamps. Changes in water quality from waterways draining the catchment could potentially impact benthic-feeding species like shorebirds, although this has yet to be tested. However, the most influential of local factors are likely to be those brought about by human population pressure and modification or loss of habitat due to development and coastal use. These factors are discussed in more detail below.

1.3 Current land uses and threats to waterbird populations Western Port is a relatively intact natural asset that is also subject to a variety of residential, agricultural, industrial and recreational uses. Industrial and residential developments are likely to continue in the short- to medium-term as the population of Melbourne continues to expand especially along the south-eastern growth boundary (State of Victoria 2002). The dominant land uses along the western shores are urban (mostly centred on the estuarine catchments) and

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agricultural. Point-source (i.e. non-dispersed) industrial impacts are highest around Hastings, in the form of refinery and shipping activities.

Low-lying land to the north of the Western Port embayment are the historic site of the Koo Wee Rup swamp, which extended from the coast inland almost to the foothills of the Great Dividing Range (Yugovic and Mitchell 2006). Conversion of this swamp to agricultural land in the early 20th century was coupled with substantial modifications to waterways and estuaries, with most now diverted and channelised (straightened), and having degraded riparian zones. This change is now known to have significantly altered sediment dynamics in Western Port and is partially implicated in detrimental changes within the bay, such as the loss of seagrass (Wallbrink et al.

2003).

Along the eastern shore, bordering the western edge of the Strzelecki Ranges, foothills and alluvial plains have been cleared and are now used for livestock grazing. Urban use in this area is low and confined to the narrow coastal plain, although agricultural inputs including nutrients, pesticides, and herbicides are likely to be relatively continuous and of moderate intensity. A few small-scale industrial developments, mainly associated with agriculture, are located near the coast and may, from time-to-time, release effluent that can negatively affect waterbirds (especially those foraging at the outlets of waterways discharging these point-source pollutants). The southern boundary of Western Port is Phillip Island, which is a popular holiday destination and has localised areas of high urban density. Bass Coast Shire (which includes Phillip Island) experienced a 2.35% resident population growth rate between 2000 and 2010 (Bass Coast Shire Council Annual Report 2009/2010), placing increasing pressure on the region’s natural values. Furthermore, Pakenham (Cardinia Shire), located in the northern region of the catchment, is one of the growth corridors for Melbourne 2030 (State of Victoria 2002) and the shire is the third-fastest growing local government area (LGA) in Victoria (www.abs.gov.au, accessed 31 May 2011). This means that increasing numbers of people will access Western Port for recreational purposes.

In addition to dominant land uses on the coast and in the hinterland, the intertidal and subtidal areas of the bay are subject to moderate–high levels of recreational use, including fishing and boating (motorised, sailing, jetskis, hovercraft and paddled craft). Recreational fishing, both boatbased and shore-based (angling) is widespread around the bay. Commercial license buybacks commenced in 1999 and continued until 2007, when commercial fishing operations ceased. At present commercial line fishing is still permitted in Western Port but few licences are held (D. Ball pers. comm.). Reported catches of all commercial fish species declined between 1980 and the last reporting period in 2007/2008 (DPI 2008).

The presence of relatively large (and growing) populations of people in the catchment may place substantial pressure on important habitat for waterbirds or on the birds themselves. Threats to waterbirds include those whose impacts are indirect (through habitat loss) and those that directly affect birds (causing bird injury or mortality).

Threat of habitat loss may be due to the following factors: • foreshore development • introduced plant species (e.g. Spartina) • removal of grazing or high-intensity grazing (case specific—when roosting, shorebirds prefer areas of very low and sparse vegetation best maintained by livestock grazing, but other waterbird species like ducks and swans use saltmarsh, which is damaged by livestock) • revegetation works (tall plantings that obscure the bird’s view at high-tide roost sites, reducing roost suitability) • potential habitat loss due to predicted sea level rise (loss of roosting and foraging habitats, changes to patterns of sedimentation).

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Direct threats to birds include: • • • • • • •

damage or loss of nests or young birds through trampling or crushing by walkers and vehicles fox and cat predation ingestion of rubbish (e.g. plastic bags or discarded fishing gear) entanglement in discarded fishing line and fishing nets foxes, dog and cat predation hunting (where applicable) disturbance.

1.3.1

Disturbance

Disturbance can be particularly important in coastal areas which attract large numbers of people, and it needs special management because the damage often arises unwittingly when well-meaning people are unaware of the potential consequences of their actions.

One of the most widespread threats to waterbirds in Western Port (and the Greater Melbourne region) is that of disturbance via the presence of people, companion animals and vessels (Dann et al. 1994, BOCA 2005, Antos et al. 2007, Williams et al. 2009). Specific causes of disturbance (direct or indirect) to waterbirds include: people – walkers and joggers, fishers and bait gatherers, campers, picnickers, horses and riders companion animals, usually dogs motorbikes and off-road vehicles water craft, including yachts, jet skis, canoes, surf skis, paddle boards - approach of, or passage past roost/foraging/breeding sites - mooring or landing near roosting birds (and disembarkation of passengers and dogs) - launching • foxes and other predators disturbing birds at night roosts • predators following human passage (e.g. ravens, foxes).

• • • •

Disturbance can have several consequences on birds. In the short term, these can include increased energy expenditure when roosting or foraging birds are forced to fly for varying periods or distances until the disturbance has passed. This can be especially critical for migrants which need to put on weight before making long-distance migrations (e.g. to breeding grounds in Arctic Siberia) and can reach a point where specific sites become too energetically costly for shorebirds (Rogers et al. 2006). Consequences of disturbance can also include increased risks of mortality to breeding birds or their young when adults are distracted by protecting their nests against predators (Weston and Elgar 2007). Disturbance of roosting and foraging birds potentially has a cumulative impact on waterbird populations, in terms of reductions in breeding success and survival, and increases in adult, juvenile and hatchling mortality. This is especially true where increased recreational use is coupled with elevated sea levels, the latter predicted under current climate change scenarios (State of Victoria 2008).

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1.3.2

Climate change risk assessment

The manner in which climate change will affect waterbird populations in Western Port is considered here to relate to loss of habitat through sea level rise, increasing storm surges, erosion of high-tide roosts like sandy spits and beaches, and substrate mobilisation. The process by which these changes will occur is still the subject of much discussion and research (McInnes et al. 2008, Boon et al. 2010, J. Peterson pers. comm.).

With this in mind, a very simplistic approach is taken to assess climate change risk â&#x20AC;&#x201C; the direct loss of high-tide habitats is investigated by simulating a sea level rise of 0.8 m in order to quantify the resultant loss of roosting area to inundation. This method is generally referred to as the â&#x20AC;&#x2DC;bath-tubâ&#x20AC;&#x2122; or inundation approach and is a passive model assuming no sea surface turbulence (IglesiasCampos et al. 2010, P. Debicki pers. comm.). A sea level rise of 0.8 metres was chosen in accordance with the planning benchmark established in the Victorian Coastal Strategy (State of Victoria 2008).

The bath-tub approach functions by raising the sea level by a defined amount until it reaches the equivalent height on land (Ministry for the Environment 2008) and has a number of advantages and limitations. The advantage is its simplicity and fast production of inundation maps. The approach is also easily understood by non-experts. The main limitations are that it does not consider coastal protection structures (e.g. seawalls) (Iglesias-Campos et al. 2010) and information on natural sedimentary processes (Jelgersma 1994). These natural processes are driven by wind, waves and tides and availability of sediment in the system, and can provide for the vertical accumulation (aggradation) of sand and mudflats that may otherwise prevent or delay permanent inundation. As a result, the bath-tub approach is described as exaggerating the effects of sea level rise (Jelgersma 1994, Iglesias-Campos et al. 2010). Nevertheless, it provides an inexpensive approach for an initial assessment of locations or sites that may be at risk from climate change and thus, require further investigation or special protection until more information can be obtained regarding their level of risk.

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1.4 Project objectives This project was designed to be an important step in the process to produce an effective, welltargeted management program that works with land managers and local communities to ameliorate threats to waterbirds in the bay.

The strategy for achieving this was to: 1. Establish the relative importance of high-tide roosts and foraging areas throughout the Western Port Ramsar site so that management attention can be directed where the greatest benefit can be achieved. This required detailed analysis of existing bird data and targeted field studies to fill information gaps and improve scientific rigour underlying management recommendations.

2. Produce clear and accurate maps of key habitat areas, at an appropriate scale, so that the community and site managers have accurate information about which areas are most important for waterbirds (especially in relation to resource distribution, tidal cycles and seasons).

3. Elucidate threats operating at each of the key areas and prioritise appropriate mitigation measures for those areas.

4. Make a preliminary climate change risk assessment to waterbird habitat associated with projected sea level rises. This was done using Digital Elevation Models (DEM) developed by DSEâ&#x20AC;&#x2122;s â&#x20AC;&#x2DC;Future Coastsâ&#x20AC;&#x2122; program. This will aid in the future identification of priority areas for protection of existing habitat, and the provision of new habitat. For example, by protecting areas of suitable topography containing suitable substrate, allowances may be made for the development of new habitat at higher elevations within the estuarine system as sea level rises.

5. Consultation with stakeholders and community members to begin the development of management programs to address key threats and protect important waterbird sites.

The management program derived from this project will be integral to the future protection and restoration of key habitat areas for migratory shorebirds and other waterbirds in Western Port.

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2

Methods

Bird names used in this report follow the nomenclature of Christidis and Boles (2008).

2.1 Site description There are between 15 and 20 sites (grouped or single) within Western Port (Figure 3) that are the focus of shorebird and waterbird monitoring as they are known to support substantial congregations of birds at various times (Loyn 1978, Loyn et al. 1994, Loyn et al. 2001). All but one of these sites (Hanns Inlet) are high-tide locations where shorebirds and other waterbirds congregate to roost whilst their foraging habitat on the intertidal mudflats is submerged. High-tide roosts are usually characterised by sandy shores or spits, or rocky platforms, or, occasionally, open areas of exposed mudflat. Some species also roost in partially submerged mangrove bushes. Most roost sites are fringed by saltmarsh (sometimes containing brackish or brine swamps), mangroves or coastal Melaleuca scrub. A few sites like Bunyip River and Yallock Creek are bordered by pasture. Approximately one-third of sites fall within national parks (both terrestrial and marine) with the majority of these occurring on French Island. Several sites occur in areas of high human use â&#x20AC;&#x201C; Hastings, Warneet, Tooradin and Observation Point.

Figure 3. Map of Western Port showing key waterbird sites (green stars).

2.2 Data acquisition Non-spatial and spatial data used for analyses and mapping of waterbird habitat were acquired from several sources: Bird Observation & Conservation Australia (BOCA), Victorian Wader Study Group (VWSG), Birds Australia (BA), the Department of Primary Industries (DPI), Fisheries Victoria (FV) and the Department of Sustainability and Environment. Anecdotal information from BOCA counters, VWSG members, Parks Victoria staff and local community

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members was also used at different stages of the project to guide mapping where other data were not available.

2.2.1

Waterbird monitoring data

The BOCA Western Port Survey commenced in 1973 and has been conducted at least thriceyearly since then by volunteers (BOCA 2003). In the early years of the survey, counts were conducted five times a year: autumn, winter, spring and twice in summer. From 1995 onwards, two counts (autumn and spring) were discontinued due to the count effort involved and the availability of volunteer counters. The number of sites counted each year has varied over time in response to changes in waterbird distribution and changes in habitat suitability (e.g. drying of coastal swamps due to reduced rainfall meant that counts at some sites ceased).

The surveys were conducted by teams of volunteers who visited bird roosting sites on selected days, close to high tide, and counted or estimated the number of birds present. Survey dates were chosen to coincide as closely as possible with the previous yearâ&#x20AC;&#x2122;s count date for any given season.

Data were collated by BOCA and made available to this project in the form of Microsoft Excel spreadsheets.

The VWSG has been undertaking shorebird monitoring activities in south-east Australia using capture by cannon netting since 1978 (Minton 2006). Migratory shorebirds and a resident species (Australian Pied Oystercatcher) were most commonly targeted in cannon net catches in Western Port. As with the BOCA Western Port Survey, locations of activities have varied over time but usually focus on a selection of high-tide roosting sites that are known to be used regularly by birds.

Birds captured by cannon netting are marked using a unique numeric identifier inscribed on a metal band (usually) applied to the lower leg. Recaptured birds can be identified from this leg band number. Data from captures and recaptures are held by the VWSG and were provided to the project in form of Microsoft Excel spreadsheets.

2.2.2

Spatial data

BA has completed and made publicly available a series of digital maps that illustrate areas where birds are counted by both Australasian Wader Studies Group (AWSG) and BOCA members (refer to their website www.birdsaustralia.com.au). The spatial layers (ESRI shapefile format) containing the information on shorebird count areas in Western Port was provided by BA for use in this project.

Other spatial data were obtained from two additional sources: DPI/FV and DSE. DPI staff provided data from the Oil Spill Response Atlas, which includes mapping of important shorebird areas, roost locations, areas of significance for fauna and other information related to biodiversity management in Western Port.

All other spatial information was accessed internally through DSEâ&#x20AC;&#x2122;s Spatial Datamart (including products from the Future Coasts Program), with the exception of the saltmarsh mapping which was provided by Steve Sinclair, Arthur Rylah Institute for Environmental Research (ARI) (unpubl. data).

2.2.3

Other data

Information on monthly commercial catches of fish in Western Port was provided by FV. Meteorological and climate data were accessed through the Bureau of Meteorology website.

Streamflow data were similarly accessed through the Murray Darling Basin Authority website.

2.3 Field survey The BOCA Western Port Survey is ongoing and continued for the duration of this project. BOCA Western Port surveys were conducted in 2009 on 11 July and 21 November, in 2010 on 13 February, 10 July and 20 November, and in 2011 on 5 February. However, only data obtained up until February 2009 were used for analyses.

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In order to gain additional information about waterbirds and their habitat use at times other than during formal surveys, informal (non-targeted) surveys were conducted either as one-off counts or during other related projects. Numerous opportunistic, land-based counts were made in the spring– autumn periods of 2009/2010 and 2010/2011. At this time of year shorebirds are still in southern Australia and are most likely to be observed on mudflats or using high-tide roosts. A number of high-tide sites that are no longer counted during the Western Port survey were visited to assess their current significance. These were Settlement Rd, Corinella, Queensferry, Churchill Island and The Duck Splash. Most of these sites may be used by some birds at all stages of the tidal cycle.

The Duck Splash was a very important site for waterbirds in the early years of the BOCA Western Port Survey but the drought conditions of 1997 to 2009 reduced its use by birds to virtually zero.

Some sites that are still included in the Western Port survey were also visited at least once to determine their use by waterbirds in other parts of the season. A boat was used to explore mudflat areas in the northern and western parts of the bay on several occasions, in order to gain a better understanding of their importance to foraging birds. Estuaries were also visited as part of a concurrent project investigating estuarine condition.

Opportunistic count data are used here for two purposes: to supplement existing information that identifies important foraging areas for waterbirds; and to identify areas requiring further investigation. Observations on breeding or potential breeding (revealed by the presence of unfledged or juvenile birds, e.g. cygnets) were noted.

2.4 Data analysis 2.4.1

Preliminary trend analyses

Data from the BOCA Western Port Survey (1973–2009) were inspected by eye for errors or duplication. Species for which there were substantial data gaps (years missing) or for which few birds were counted and only at a very small number of sites, were removed from analysis.

Generally, these were species that were only counted very occasionally, for example, Blackfronted Dotterel, Black-tailed Godwit, Hooded Plover, Lesser Sand Plover, Nankeen Night Heron and Sanderling. Counts of birds for each species in each foraging guild (i.e. fishers, ducks, migratory shorebirds, etc.) were summed and plotted against date to search for trends in the data over time. For example, all three grebe species (Hoary-headed Grebe, Australasian Grebe and Great Crested Grebe) were combined into a total count for the foraging guild ‘Grebes’.

When patterns of interest were detected (e.g. upward or downward trends), total counts of each species in that guild were plotted separately against date. Where a trend was observed for a given species, that species was plotted separately for each site that had consistent count effort. For example, the guild Grebes (containing three species) exhibited a downward trend between 1973 and 2009. When each grebe species was plotted separately, Hoary-headed Grebe was found to be the primary driver of this trend, and the decline in this species was most evident at one site (HMAS Cerberus settling ponds), with erratic changes in numbers observed on the sea elsewhere.

This simple analytical approach was used to elucidate trends of each species in each guild at every site.

2.4.2

Modelling of trends

On the basis of the preliminary trend analyses, a simple modelling approach was adopted to determine if trends were statistically significant and to explore covariates that might explain the trends observed. Count data for each season (late summer, winter and early summer) in each year (1973–2009) were analysed using generalised linear models in R 2.10.1 (R Development Core Team 2006). Species in the guild ‘Rails’ were excluded from modelling analyses owing to insufficient data.

Environmental covariate data used in the modelling were:

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• mean monthly rainfall for four Victorian regions: local (Koo Wee Rup gauge), north-central (Goorambat gauge), eastern (Clydebank gauge) and western (Willaura gauge) • Darling River and Murray–Darling Rivers streamflow (maximum monthly streamflow from Burtundy and Lock 9 gauges, respectively) • Southern Oscillation Index (temporal fluctuations in air pressure differences between Tahiti and Darwin).

A single source of data was used as a biological covariate in the modelling: • monthly commercial fish catch in kilograms for three species combined (Yellow-eyed Mullet Aldrichetta forsteri, King George Whiting Sillaginodes punctata, and Southern Sea Garfish Hyporhamphus melanochir) for 1978 to the close of the fishery in 2007.

Fish caught during commercial operations are unlikely to be potential prey items for fish-eating birds because those of interest to commercial fisheries are usually too large for the birds to catch and eat. It is more likely that birds are preying on fish when they are juveniles and probably still in their seagrass nursery grounds. Therefore, in order to estimate fish availability using commercial catch records, values in each year were set back by the number of years that represent the approximate time taken for that species to reach maturity and be recruited into the adult (catchable) population. The minimum ages of sexual maturity of mullet, whiting and garfish are around two, two and three years respectively (Jenkins and King 2006; G. Jenkins pers.comm.).

Thus, fish caught in 1978 were considered available as prey for birds in either 1976 or 1975, depending on the species.

Environmental and biological covariate data were analysed using generalised linear models, as above. For Holarctic Shorebirds, only the maximum summer count in each year was used for analyses (i.e. maximum count from either November or February). This is because adult birds are absent in winter and counts during this time are not representative of the whole population. In the case of Double-banded Plover, which is a winter migrant from New Zealand, only winter count data were used in analyses. For all other species, count data for all three seasons were retained in analyses to explore the seasonal variation in trends. Maximum values of the Akaike Information Criterion (AIC) were used to select the most parsimonious model from a selection of models incorporating the nine explanatory variables.

2.4.3

Analyses of site importance

A simple ranking exercise was undertaken to determine the relative importance of each site to waterbirds. This ranking was conducted using data from all waterbird species (in contrast to the modelling which used data only from species counted relatively consistently). Several species were excluded because they were only counted on several occasions during that period (e.g.

Sanderling was counted once).

Total abundance and number of species for each site were used to define importance. In other words, sites having consistently large numbers of birds and high numbers of species were deemed to be more ‘important’ than sites with consistently lower abundances and fewer species. This criterion was used to determine rankings for each site varying from least important (low abundance and low numbers of species) to most important (high abundance and high numbers of species).

Total abundance and number of species in each year was plotted to assess the pattern of importance among sites over time. A threshold (using abundance data) was computed for assigning sites to a high importance category in each year. This was done by calculating the total abundance of each species in every year, then taking the maximum of these values (over all years) and summing them across all species. This summed value was then averaged by the number of years.

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Total annual abundance for every site in each year was log(10)-transformed (to linearise the data and make site-by-site patterns clearer) and compared against the threshold value (also logtransformed). Sites having a higher log(abundance) than the threshold were scored one and all others scored zero. This was computed for every year and then the total score for each site was summed across all years. Sites with a higher score ranked above sites with a lower score.

2.5 Movements of banded birds Three shorebird species have been marked and recaptured by the VWSG in Western Port in sufficient numbers to allow an exploration of movement patterns. These are Red-necked Stint, Curlew Sandpiper and Bar-tailed Godwit. Details of birds banded and locations and dates of captures/recaptures were extracted from the VWSG database. Recaptures at sites different to original capture were sorted separately and categorised according to the bird’s age at first capture, its age at subsequent recapture, and the time elapsed between capture and recapture. Recaptures of juvenile (first year) birds were excluded from movement analyses as juveniles are assumed to use habitat differently to adults and are not considered representative of the species’ broader habitat preferences.

In order to detect movements that might represent use of multiple roost sites by discrete groupings of birds, recaptures made in the same non-breeding season as the previous capture were analysed.

Individuals recaptured at a different site within 48 hours were excluded from the analysis, to reduce the potential for behavioural bias caused by short-term avoidance of capture sites by birds.

As birds tend to congregate in the same flock at high tide, movements of flocks between roost sites was inferred on the basis of movements of individuals. These were plotted on a map to visualise the spatial extent of daily or monthly movements.

2.6 Mapping 2.6.1

Existing mapping information

Mapping of ‘important shorebird areas’ has been previously undertaken (prior to 2009) by BA and provides digital information about the maximum known extent of shorebird habitat use in a given area. These were constructed in consultation with several BOCA members and are intended primarily to delineate the areas counted during the Western Port survey. Some count areas that have been recently added to the Western Port survey (e.g. Chambers and Long Points on Phillip Island) are not included in the BA mapping.

BA maps exist in the form of polygon layers (shapefiles format) covering all of Victoria. These spatial layers for Western Port were uploaded into ArcView 3.2 (ESRI, Redlands, USA) together with the most recent aerial photography (December 2009, DSE) to assess their coverage and spatial accuracy. Layers for shorebird roost locations and other important sites (in terms of ‘biodiversity values’ that may be affected in the event of an oil spill) taken from the Oil Spill Response Atlas (DPI) were similarly added into ArcView. Other relevant data included in the spatial analyses were: seagrass and saltmarsh mapping, special management areas, National Park boundaries and other biological and environmental information from within the Western Port Ramsar site.

All spatial layers were converted to GDA94 zone 55 projections (if not already projected using these coordinate systems) using ArcCatalog 9.3.1 (ESRI, Redlands, USA). Draft maps containing this information were provided to shorebird/waterbird counters (BOCA, VWSG and BA) for comment on their accuracy. A combination of all spatial datasets plus feedback from counters was used to guide subsequent assessment and construction of new waterbird maps. The horizontal accuracy of the newly constructed polygons depends on the resolution of the aerial photo (1:10 000), the horizontal accuracy of other spatial data used and anecdotal evidence from observation by counters.

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2.6.2

Construction of waterbird maps

The above spatial data were simultaneously assessed with information gathered during opportunistic field surveys, the authors’ prior knowledge of the area and observations from BOCA counters, other members of the Victorian ‘shorebird community’ and local managers and residents (Parks Victoria officers and local land owners). Aerial photography together with saltmarsh, mangrove, seagrass and coastal 0.5 m contour spatial data were simultaneously used to delineate boundaries of existing or new polygons in ArcView.

Two spatial layers were created to display two levels of information: high-tide roosts and important foraging areas (the latter mostly concentrated on the intertidal zone). High-tide roost polygons were constructed predominantly by amending existing polygon layers, with the addition of several new polygons. Foraging area polygons were created almost wholly from information gathered during this project, drawing on the large body of anecdotal information and unpublished accounts contributed by shorebird and waterbird counters. Topographic information contained within a 0.5 m coastal DEM (supplied by Spatial Information Infrastructure, DSE) was used to guide delineation of high-tide polygon boundaries. The vertical land-based modelling of the DEM is accurate to approximately 10–15 cm.

2.7 Assessment of climate change inundation risk The potential impact of sea level rise on high-tide roost sites was measured in terms of loss of area from inundation using the ‘bath-tub’ approach (or inundation model). This was done by calculating the total area of each high-tide roost site using the newly created spatial layer (see Section 2.6) and intersecting it with existing 0.5 m DEM. The area between 1.56 m (current Highest Astronomical Tide at Stony Point tide gauge: McInnes et al. 2008) and 2.38 m above mean sea level was determined to be the area at risk from a sea level rise of 0.8 m by 2100. For the purpose of the present analysis, the 1.5 and 2.5 m contour lines were used for inundation area calculations as these were readily available within the Future Coasts DEM dataset and are considered to be representative of the range of sea level rises that are predicted to occur bay-wide (up to 1.1 m in the north). This range approximately reflects the average high-tide mark and therefore, the tidal upper limits with a 1 m sea level rise. Results of the inundation area calculations are expressed as a proportion of the current total area (in square metres) that will become unavailable at high tide at each individual site, and of all sites combined.

2.8 Community engagement Significant time and effort was invested in talking with community members, including the members of the community involved in shorebird monitoring as volunteers (the majority of BOCA and VWSG members), staff in management agencies, and members of the public. The intention of these conversations was to collate information from anecdotal accounts and previously unpublished observations which is relevant to understanding how waterbirds use Western Port.

Existing contacts and parallel research projects were used as a means of communicating beyond the initial project stakeholder group. A high priority was placed on opportunities for project staff to engage with local community members whilst in the field.

Information about threats occurring in Western Port was derived largely from discussions with land managers (usually Parks Victoria staff) and waterbird/shorebird counters. Observations made during field surveys were also drawn upon to compile a list of threats operating at key sites.

As part of the broader Western Port Welcomes Waterbirds project, a separate (concurrent) study was conducted by researchers at Deakin University to investigate perceptions of bay users and residents of waterbirds and their habitat (Christie et al. 2010). That study targeted beach users and residents at four sites: Hastings, Observation Point, Stockyard Point and Warneet. The details of that study can be found at http://www.ccb.vic.gov.au/waterbirds.html.

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3 Results 3.1 Opportunistic field surveys Informal land-based surveys (on the mainland) revealed that some sites which are no longer counted during the BOCA Western Port Survey continue to support low numbers of birds, representing few species. The majority of these were mainland sites. In contrast, some sites on French Island which have been unproductive in the last 12 years of reductions in average rainfall (1997â&#x20AC;&#x201C;2009) due to drying of swamps, contained substantial numbers of birds in the 2010â&#x20AC;&#x201C;2011 springâ&#x20AC;&#x201C;summer season.

Among the most important of these was The Duck Splash on the northern shores. A single visit there in April 2011 revealed large numbers of various waterbird species including 215 Australian Shelduck, 850 teal (approximately 50% being Chestnut and 50% being Grey), 30 Australasian Shoveler, 80 Pacific Black Duck, 53 White-faced Heron, 170 Australian White Ibis, 2 Royal Spoonbill, 10 Masked Lapwing, 131 Black Swan and 22 Cape Barren Geese. These changes in waterbird use appear to have coincided with increased rainfall through winter and spring of 2010 (National Climate Centre 2010), and a resultant increase in wetland availability.

Non-targeted boat-based counts were made from channels in the northern and western parts of the bay (Figure 4). Counts of birds on mud banks were done from a boat as it was not possible to walk on the muddy substrate. Several distinct intertidal areas had substantial numbers of birds foraging or roosting. Middle Spit mud bank, between French Island and the western shoreline of Western Port, consistently had Black Swan, gulls, large wading birds (herons and ibis), cormorants, resident shorebirds (typically Australian Pied Oystercatcher) and migratory shorebirds (predominantly Curlew Sandpiper, Eastern Curlew, Red-necked Stint and Whimbrel during spring to autumn months). Barrallier Island/ north-west French Island tidal flats had small shorebirds near channel edges, plus ibis, Black Swan, herons, gulls and oystercatchers foraging at low tide.

Watson Inlet in the north-western part of the bay supported Black Swan, large wading birds (herons, ibis and Royal Spoonbill) and Common Greenshank (spring to autumn months) on each of several visits. The mud banks on either side of the North Arm channel (north section) were frequently occupied by foraging groups of small shorebirds during the spring to autumn months (usually Red-necked Stint). A low rocky island (reef) north-east of Chicory Lane channel and immediately east of Barrallier Island (referred to hereafter as Chicory Lane reef) was found on every visit (approximately 20) to serve as an important pre-roost (i.e. a roost used by birds on the rising or falling tide that is submerged at high tide) for shorebirds that use Barrallier Island. Birds also used this roost on lower tides when it was still exposed, or when disturbed off Barrallier Island.

The intertidal areas of Hastings Bight were found to attract foraging gulls, large wading birds (herons, ibis and spoonbills), oystercatchers, cormorants, Black Swan and Australian Pelican. Two wrecks, which are located on the mudflats in Hastings Bight, provided a convenient and largely undisturbed roosting site for Australian Pelican, gulls, cormorants and oystercatchers. Similarly, an abandoned pontoon near the entrance to Yaringa Marina was frequently used as a roost by gulls (both Silver and Pacific), Australian Pied Oystercatcher and White-faced Heron. A nearby sand bank provided a pre-roost for these species and cormorants.

Crawfish Rock in the centre of the main north-west channel, is an important roost for gulls, terns (Crested Tern but also a single record of Common Tern and White-fronted Tern) and cormorants (including a single record of a Black-faced Cormorant).

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Importantly, channel markers bay-wide were consistently used as perching sites by cormorants, especially Pied and Little Pied Cormorants. Perching sites are essential to cormorants because of their need to dry their plumage and digest their food between foraging trips.

Surveys of Bass Bay and the Bass River estuary, which occurred as part of a concurrent project on developing methodologies for assessing estuarine condition (Index of Estuarine Condition; ARI and Deakin University) revealed substantial numbers of waterbirds using the Bass River delta.

Warrangine, Watson, Cardinia and Bunyip estuaries tended to have smaller numbers of different waterbird species that varied from season to season. The entrances to these estuaries generally supported moderate to large numbers of waterbirds.

The north-west shores of French Island were explored by boat on a number of occasions during the 2010/2011 spring–summer season. Acting on information received from PV (M. Douglas pers.comm.), a sandy beach about 300 m south of Scrub Point (referred to hereafter as Mick’s Beach), north-west French island, was found to contain small flocks of Red-necked Stint and Redcapped Plover at high tide, and breeding pairs of Australian Pied Oystercatcher. Eastern Curlew and Common Greenshank were observed to use the saltmarsh at Scrub Point and behind Mick’s Beach during inclement weather. In addition, Black Swan, White-faced Heron and Little Pied Cormorant were found to use the mangroves and mudflats in front of this beach on rising and falling tides.

Figure 4. Aerial imagery of Western Port showing opportunistic survey coverage.

‘BA mapped count areas’ represents sites visited by BOCA counters during formal Western Port surveys, and was mapped by Birds Australia prior to 2009 (see section 2.6.1).

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3.1.1

Observations of breeding

Black Swan, Chestnut Teal, Grey Teal, Pacific Black Duck, Australasian Grebe, Caspian Tern, Fairy Tern and Australian Pied Oystercatcher were the only species for which direct observations of breeding were made during opportunistic surveys. Black Swans were found to breed in inundated fresh and saline swamps in the north-west of French Island. Freshwater swamps included those where counting has been conducted in the past (Bullock and Decoy swamps) plus adjacent inundated paddocks. Swans were also observed nesting in inundated saltmarsh along the western shoreline of French Island. In addition, cygnets were observed in most places where swans congregated, for example, the northern, western and southern shores of French Islands, Bass Bay and in estuaries such as Warrangine.

Fairy Tern and Caspian Tern are known to nest intermittently on Rams Island in summer and they were observed nesting there during the 2009/10 summer. Nest loss in past years has been noted by PV French Island staff. It is thought that losses due to storms and king tides contribute significantly to nesting failure (M. Douglas & C. Minton pers.comm.). Predation of nests was also suspected, but despite installing remote cameras during the 2009/10 summer, no observations of nest predation were obtained. Australian Pied Oystercatchers were observed to breed on the northwest corner of French Island, in amongst the saltmarsh where suitable sandy spots with good visibility are available for nesting scrapes. Local breeding success of oystercatchers can also be inferred by the presence of juvenile oystercatchers in flocks at Fairhaven and Barrallier Island in autumn (both 2010 and 2011).

Grey Teal with ducklings were observed on Bullock Swamp in summer 2009/10. Chestnut Teal and Pacific Black Duck were observed with ducklings, and Australasian Grebe were observed nesting on the Cerberus settling ponds in summer 2010/11. It is highly probable that nesting also occurred on the swamps on French Island given the amount of surface water available there, although no direct observations were made on sporadic visits.

The following breeding accounts were provided by Parks Victoria staff on the basis of their observations (see Acknowledgements). The first pair of Cape Barren Geese arrived on French Island about 10 years ago. They nested successfully in a pine tree on private property, the nest being placed approximately 1.5 m off the ground, probably in order to avoid trampling by cattle that grazed there. Since that time, the numbers of Cape Barren Geese using French Island has increased to the hundreds and extensive breeding occurs particularly around farm dams on private property. In addition to the geese, Australian Shelduck were also observed breeding (in reedy swamps) on French Island during the 2010/2011 summer. On nearby Phillip Island counts show there are over 400 Cape Barren Geese including many breeding pairs (R. Jessop unpub. data).

3.2 Population trends and responses to explanatory variables Waterbirds as a whole were found to have significantly declined between 1974 and 2009 (Z = â&#x20AC;&#x201C; 3.334, SE = 0.004, P = 0.001): 1973 was omitted because only a single survey season (December) was undertaken in that year. Figure 5 shows the total annual count (summed across summer and winter counts only) and the maximum annual count (from any given season) for each year of the survey. The pattern of decline was stronger when summing counts over seasons compared with the maximum count in any year.

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70000

Maximum annual count Total annual count

60000

Abundance

50000 40000

30000 20000

10000 0 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008

Figure 5. Trends in all waterbirds combined between 1974 and 2009.

Total annual count is the sum of all summer and autumn counts in each year. Maximum annual count is the maximum count from any given season in each year.

3.2.1

Modelling

Virtually all guilds of waterbirds—Australasian shorebirds, fishers, ducks, grebes, gulls, Holarctic shorebirds, large wading birds and Black Swan—showed a clear downward trend over time. When individual species were plotted separately, a substantial number of species were found to also exhibit this trend (Table 2). Results from generalised linear modelling indicated that declines for 16 species were significant (Table 2). Several species appeared to have decreased in numbers between 1997 and 2009 (the most recent years of reduced rainfall), but were not found to have significantly declined throughout the whole survey (Chestnut Teal, Common Greenshank, Fairy Tern, Pacific Black Duck, Royal Spoonbill and Ruddy Turnstone). Four species were found to have significantly increased throughout the survey—Australian Pied Oystercatcher, Bar-tailed Godwit, Red-necked Stint and Whimbrel. Of these, both Bar-tailed Godwit and Whimbrel showed a downward trend between 1997–2009, but overall, an increase throughout the survey.

Only in nine cases were there any significant covariation between total count and one or more other explanatory variables (Table 3). For these nine species, three explanatory variables were found to explain a significant amount of the variation, singly or in combination with one another.

These were commercial fish catch, rainfall in western Victoria and streamflow from the Darling River (Table 3).

Commercial fish catch varied significantly with trends in several fish-eating species (Caspian Tern, Great Cormorant, Little Black Cormorant and Little Pied Cormorant), but also with trends of several intertidal foraging shorebird species (Common Greenshank, Eastern Curlew, Grey-tailed Tattler and Whimbrel) that are not usually considered fish-eaters (although Common Greenshank does include fish in its diet). Trends in one duck species (Australian Shelduck) varied significantly with rainfall in western Victoria, although this relationship was complicated by the effects of season.

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For six species the most parsimonious model contained only a single explanatory variable: these were Great Cormorant, Little Black Cormorant, Little Pied Cormorant, Eastern Curlew, Greytailed Tattler and Whimbrel, which were positively correlated with fish catches. The most parsimonious model for Common Greenshank included both fish catches and rainfall in northcentral Victoria, although the relationship with rainfall was not significant.

For all other species, the most parsimonious model contained one or more explanatory variables (depending on the species) but none varied significantly with trend over time, and have therefore not been reported here.

Figure 6. The Australian White Ibis commonly feeds on the tidal mud flats of Western Port.

Photographer Peter Menkhorst.

Figure 7. Grey-tailed Tattlers roosting at high tide.

Photographer Peter Menkhorst.

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Table 2. Population trends in waterbird species from 1973–2009.

Only species with relatively consistent counts over time are reported here. Species with erratic counts or numerous zero counts are excluded. Coefficient estimates, standard errors and

Guild Australasian shorebirds

Ducks

Fishers

Grebes Gulls Large wading birds

Holarctic shorebirds

Swans

Z values are derived from output of modelling analyses.

Species

Trend

Australian Pied Oystercatcher Double-banded Plover Masked Lapwing Red-capped Plover Sooty Oystercatcher Australian Shelduck Chestnut Teal Grey Teal Musk Duck Pacific Black Duck Australian Pelican Caspian Tern Crested Tern Fairy Tern Great Cormorant Little Black Cormorant Little Pied Cormorant Pied Cormorant Hoary-headed Grebe Pacific Gull Silver Gull Australian White Ibis Great Egret Royal Spoonbill Straw-necked Ibis White-faced Heron 1, 3 Bar-tailed Godwit Common Greenshank Curlew Sandpiper Eastern Curlew Grey-tailed Tattler Pacific Golden Plover Red Knot Red-necked Stint Ruddy Turnstone Sharp-tailed Sandpiper 1 Whimbrel Black Swan

Increasing Declining Declining Declining Variable Declining Declining Declining Variable Declining Declining Variable Declining Declining Declining Declining Declining Declining Declining Variable Declining Declining Variable Declining Variable Declining Stable (increasing) Declining Declining Declining Declining Declining Variable Stable (increasing) Declining Variable 2 Variable 3 Variable

Coefficient estimate 0.032 –0.003 –0.025 –0.008 –0.0004 0.027 0.016 –0.035 0.004 –0.004 –0.033 0.004 –0.050 –0.007 –0.054 –0.016 –0.037 –0.008 –0.050 –0.004 –0.034 –0.014 0.002 –0.003 0.025 –0.028 0.012 –0.010 –0.029 –0.010 –0.063 –0.030 0.002 0.011 0.002 0.011 0.031 –0.012

Standard error 0.004 0.605 0.005 0.004 0.010 0.008 0.010 0.013 0.011 0.010 0.006 0.006 0.009 0.016 0.011 0.010 0.006 0.006 0.015 0.006 0.006 0.006 0.011 0.008 0.017 0.006 0.004 0.007 0.008 0.004 0.013 0.010 0.019 0.004 0.008 0.011 0.012 0.007

Z value

P

7.413 –0.004 –4.805 –2.097 –0.039 3.412 1.614 –2.793 0.330 –0.402 –5.751 0.719 –5.696 –0.451 –5.105 –1.627 –5.658 –1.379 –3.473 –0.611 –5.352 –2.560 0.202 –0.454 1.487 –4.906 2.837 –1.522 –3.778 –2.352 –4.743 –3.182 0.122 2.966 0.275 0.962 2.480 –1.553

<0.001* 0.997 <0.001* 0.036* 0.969 0.001* 0.107 0.005* 0.742 0.687 <0.001* 0.472 <0.001* 0.652 <0.001* 0.104 <0.001* 0.168 <0.001* 0.541 <0.001* 0.011* 0.840 0.650 0.137 <0.001* 0.005* 0.128 <0.001* 0.019* <0.001* 0.002* 0.903 0.003* 0.784 0.336 0.013* 0.120

* significant at 0.05 1 single outlier removed in each case 2 this species shows a strong downward trend between 1996–2009 but overall, an increase. Thus, estimates indicate a significant increase from 1973–2009 3 these species show a strong downward trend between 1996–2009 but overall, the trend is either variable (Black Swan) or increasing (Bar-tailed Godwit)

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Table 3. Summary of modelling results.

Only species for which one or more explanatory variable significantly co-varied with count data are reported here (all P<0.05 and indicated by ). The nature of that correlation is indicated with either a + (positive) or a – (negative), where possible to elucidate.

Fish

Rainfall

Darling

Sign. decline?

catch

west Vic

streamflow

(Table 2)

Common Greenshank

+

N

Eastern Curlew

+

Y

Grey-tailed Tattler Whimbrel

+ +

Y N*

Caspian Tern Great Cormorant

+

Little Black Cormorant Little Pied Cormorant

+ +

Australian Shelduck

No decline Y N Y

†

Y

* no decline between 1973–2009, but a strong downward trend during recent years of reduced rainfall 1996–2009 † the influence of this variable was dependent on season and precluded a simple indication of nature of relationship

3.2.2

General species by site trends

There was large variability in trends of each species at each site for which data were sufficient for analysis. The dominant trend was of a decrease in total count from 1974–2009 (Appendix 1). It was clear that, despite the temporal and spatial variability in counts of waterbirds, the general trend tended to be one of decline (with few increases), reflecting the patterns detected in the modelling analyses. Of the 19 sites, 16 had more than 10% of the species (regularly recorded during counts) declining between 1974 and 2009.

There were a number of cases where a species appeared to reach a peak in numbers during the middle of the survey (usually around the late eighties to the early nineties) with a subsequent decrease after this. For example, Black Swan increased in numbers throughout the eighties at Fairhaven, Long Island and Reef Island/Bass Bay but subsequently declined. A similar pattern occurred at Observation Point, but the peak was later, occurring around the mid-nineties (data not shown). In these cases it is difficult to distinguish trends from cycles, but it is worth noting that most still exhibited a decline throughout the most recent years of reduced rainfall (1997–2009), including some that made no direct use of freshwater habitats in Western Port (notably Bar-tailed Godwit and Whimbrel).

3.3 Sites of importance In order to determine the relative importance of each site by analysing total abundances and numbers of species, some understanding of what constitutes a site was necessary. There are 26 sites (excluding those where counting has only commenced in the last 10 years) that were counted each season. For the purpose of this analysis, some sites were lumped as there is evidence that they are not functionally separate sites. For example, shorebirds are known to move from Bunyip River towards Yallock Creek as the tide rises (Loyn 1975, 1978), and they are considered as a single site for these birds (Figure 8). Similarly, birds gathering on Barrallier Island may move into nearby freshwater swamps (e.g. Bullock Swamp) depending on the tidal stage, and these areas are also considered a single site. These observations were confirmed during the current study. Additional anecdotal observations of movements by birds between sites, made during surveying and catching activities, were used to determine which sites to lump and which to keep separate. Proximity of sites to each other was also an important factor.

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Lumping resulted in 19 sites available for analysis (Table 4). Sites that were combined in this fashion were: Bunyip River and Yallock Creek, Barrallier Island and north-west French Island (NWFI), Stockyard Point, GMH drain and Pioneer Bay (collectively called ‘Pioneer/Stockyard’), Sandy Point, Hann’s Inlet and HMAS Cerberus settling ponds (collectively called Sandy Pt/Hann’s Inlet) and Reef Island and Bass Bay.

(a) 600

Bunyip Yallock

Maximum count

500

400

300

200

100

0 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

(b) 3500

Bunyip Yallock

3000

Maximum count

2500 2000 1500 1000 500 0 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Figure 8. Maximum annual counts of Australasian (a) and Holarctic (b) shorebirds at Bunyip River and Yallock Creek between 1997 and 2009.

Pioneer/Stockyard, Barrallier Island/NWFI and Bunyip/Yallock had greater total abundances and number of species than any other site (Figure 9). This was consistent throughout most years of the survey, with minor exceptions: Barrallier/NWFI 1981, 1982, 1986, 1988 & 2003; Bunyip/Yallock 1996; Pioneer/Stockyard 1981. These exceptions arose when counts were missed in one or more season at both Barrallier/NWFI and Bunyip/Yallock. In contrast, unusually low counts of Rednecked Stint and Curlew Sandpiper at Stockyard Point, which move regularly within Pioneer Bay, appear to have contributed to the low numbers at Blackney’s Rd in the southern portion of Pioneer Bay in 1981.

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60

Pioneer/Stockyard

55

Barrallier/NWFI

Sandy/Hanns

Bunyip/Yallock

Number of species

50

Reef/Bass Bay Rams Island

Tortoise Head

Observation Pt

45

Fairhaven

BGP

40

Warneet

Settlement Rd Long Island Queensferry

35

Churchill Island Dwyers swamp

30

Hastings

Newhaven

25 0

50000

Tooradin

100000

150000

200000

250000

300000

350000

400000

total abundance

Figure 9. Total abundance plotted against number of species for each site from 1973 and 2009.

The solid circle indicates the more important sites, and the dashed circle indicates sites of moderate importance. BGP = Blue Gum Point, French Island

The average rank of total abundance and number of species (ignoring count effort over time) placed Pioneer/Stockyard first, followed by Barrallier/NWFI and Bunyip/Yallock equal second and Reef Island/Bass Bay fourth.

The threshold for assigning sites to the ‘high importance’ category was calculated to be log10(4006) = 3.6. For the purpose of determining site importance in each year, data from 1973 and 2009 were excluded because counts were only available for a single season (December and February, respectively). Between 1974 and 1996 the average number of sites that exceeded the threshold for ‘high importance’ was 6.0, but by 1997–2008 this average had dropped to 3.1.

Between 1997 and 2008 only four sites consistently exceeded the threshold for ‘high importance’ (Pioneer/Stockyard, Barrallier/NWFI, Bunyip/Yallock and Reef/Bass Bay). At several other sites, numbers of birds declined to levels where they were not deemed worth visiting on a regular basis and thus, count effort declined over time. As a result, from 1996 onwards Blue Gum Point was only counted twice and Settlement Rd, Newhaven, Churchill Island and Queensferry were only counted once each. Therefore, the overall importance of these sites (based on calculations from all years) relative to others was strongly influenced by large counts in early years of the BOCA Western Port Survey. As this was not deemed representative of current usage by waterbirds, only scoring derived from sites exceeding the threshold from 1997 onwards were used for the final ranking. This scoring sorted the top four sites (same as previously) into separate ranks from 1–4, but placed all other sites at an equal rank of 5.

Given the strong effect of count effort over time on determining site ‘importance’, another approach was used to calculate the final ranking order. Mean abundance per count and mean

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number of species per count, were computed for each site over all years (1973–2009). The average of these two metrics was then compared to the average of mean abundance and number of species per count between 1997 and 2009. This last step sorted all sites into a separate rank from 1 to 19 (Table 4). Figure 10 shows the distribution of these sites in Western Port using colour-coding: green for the most important sites (n=3), yellow for moderately important sites (n=8) and red for the least important sites (n=8).

Table 4. Mean abundance and number of species per count (1997–2009), total count effort (1973–2009), number of years the total abundance exceeded the threshold for ‘high importance’ and relative ranks for each major waterbird site.

No. years >threshold refers to the number of years that a site exceeded the threshold for ‘high importance’.

Site *

Mean abundance 2961.2

Mean no. of species 22.7

Number of counts** 148

No. years > threshold † 35

Barrallier Island/NWFI

3277.7

22.3

122

31

2

Bunyip River/Yallock Creek

2012.7

22.2

146

34

3

Reef Island/Bass Bay

1000.3

19.1

140

19

4

Fairhaven

1002.9

16.0

116

11

5

Tortoise Head

865.9

17.6

140

17

6

Observation Point

836.2

18.2

147

2

7

Sandy Point/Hanns Inlet

447.1

15.1

134

7

8

Warneet

449.3

9.5

119

0

9

Rams Island

225.1

9.6

135

2

10

Tooradin

529.1

7.9

126

3

11

Long Island

308.0

8.1

104

2

12

Settlement Road

118.5

6.0

64

6

13

Bluegum Point

59.0

8.0

74

1

14

Dwyers Swamp

96.4

5.6

36

0

15

Hastings

40.5

2.7

117

3

16

Churchill Island

0.0

0.0

26

1

17

Queensferry

0.0

0.0

90

1

18

Newhaven

0.0

0.0

24

1

19

Pioneer/Stockyard

Ranking 1

* sites lumped are Pioneer Bay (Stockyard Pt, GMH drain and Pioneer Bay/Blackney’s Rd), Bunyip River/Yallock Creek, Reef island/Bass Bay, Sandy Pt/Hann’s Inlet (includes Cerberus settling ponds) and Barrallier Island/north-west French Island. ** out of a maximum possible number of counts of 148 † out of a maximum of 35 years, only 1 count each in 1973 and 2009 (December and February, respectively) so excluded from analysis

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Figure 10. Distribution of sites in Western Port and their relative â&#x20AC;&#x2DC;importanceâ&#x20AC;&#x2122;, based upon rankings of total abundance and number of species.

Green circles show the three highest-ranked sites, red circles the eight lowest-ranked sites, and the yellow circles are sites intermediate in importance. Blue shading indicates the Ramsar site.

Figure 11. Aerial view of Barrallier Island and associated mudflats (foreground).

North-west French Island is in the background with Middle Spit mud banks behind. Crawfish Rock is on the far right (under the plane wing), 9 December 2009. Photographer P. Menkhorst

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Figure 12. Examples of high-tide roosting sites for shorebirds in Western Port, 9 December 2009.

Photographer P. Menkhorst

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3.4 Movements of banded birds Large numbers of Red-necked Stint and Curlew Sandpiper have been captured by the VWSG in Western Port since cannon-netting activities commenced in 1978 (24 485 and 10 424 respectively). In contrast, only small numbers of Bar-tailed Godwit have been caught (884) in the same period (Table 5). Almost half of the Red-necked Stint were recaptured at least once (46.2%), and of these recaptures, 16.3% were recaptured at a site different to the one where they were first encountered. Fewer Curlew Sandpipers were recaptured (22.4%) and of these recaptures, 26.5% were recaptured at a different site. While a similar proportion of Bar-tailed Godwit was recaptured (18.1%), a higher proportion of these were recaptured at a different site (38.8%).

Table 5. Details of captures and recaptures of banded shorebirds used to infer movement patterns.

Red-necked Stint

Curlew Sandpiper

Bar-tailed Godwit

24,485 11,316

10,424 2331

884 160

Recaptures moved

1841

617

62

Moved as % of recaptures

16.2

26.5

38.8

Recaptured adults moved*

127

40

0

Recaptured juveniles moved*

197

88

34

Total captured Total recaptured

* within a single non-breeding season (adult) or year (juvenile)

One hundred and twenty-seven adult Red-necked Stint and 40 adult Curlew Sandpiper were recaptured at a different site within the same non-breeding season. Of the Red-necked Stints, six birds were excluded from an analysis of movements, as the recapture occurred within 48 hours; three of these birds were excluded as they represented movements into or outside the bay and three were excluded as they were over-wintering adults. Of the Curlew Sandpipers, six birds were excluded from an analysis of movements, as the recapture occurred within 48 hours. Bar-tailed Godwit adults were not re-encountered within the same non-breeding season, precluding the use of this species for movement analysis.

Both Red-necked Stint and Curlew Sandpiper made interchangeable use of three main roost sites: Barrallier Island, Yallock Creek and Stockyard Point. This reflects the importance of these sites as discussed previously, as well as a bias caused by cannon-netting locations. The majority of movements were made between the two mainland sites, Yallock Creek and Stockyard Point. Rednecked Stint recaptures were made at all three sites, but only two birds moved directly between Stockyard Point and Barrallier Island (Table 6). Most Curlew Sandpiper recaptures were made at Yallock Creek (Table 6). Bi-directional movements of Red-necked Stint occurred predominantly between Barrallier Island and Yallock Creek, as well as between Stockyard Point and Yallock Creek (Figure 13). In contrast, virtually all bi-directional movements of Curlew Sandpipers were between Stockyard Point and Yallock Creek (Figure 13). Three Curlew Sandpipers moved between sites other than the main roosts: one from Yallock Creek to The Gurdies (just east of Stockyard Point) and two from Bullock Swamp to Yallock Creek (Bullock Swamp is close to Barrallier Island, and often used as an alternative site for birds to roost and feed over high tide).

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Table 6. Matrix showing details of movements by individual birds over different time scales.

Sites on the left hand side are original place of capture and sites at the top of each column are the place of subsequent recapture. Blue (top line in each cell) gives movements for Red-necked Stint and red (bottom line in each cell) for Curlew Sandpiper. Single species movements between sites are also provided as a proportion of the total (in parentheses).

recapture site (right) band site (below)

Barrallier Island

Barrallier Island

Stockyard Point

Yallock Creek

The Gurdies (near GMH)

Total

1 (2.9%)

20 (17.4%) 2 (5.9%)

-

20 3

26 (22.6%) 22 (64.7%)

-

28 22

1 (2.9%)

67 7

Stockyard Pt

2 (1.7%) -

Yallock Creek

48 (41.7%) 2 (5.9%)

19 (16.5%) 4 (11.8%)

-

-

2 (5.9%)

-

0 2

50 2

19 5

46 26

0 1

115 34

Bullock swamp Total

>20% 10-20% <10% sites having >5% average annual bay-wide population

Figure 13. Movements by small shorebirds detected using recaptures of banded birds.

Blue arrows are movements made by Red-necked Stint and red arrows are for Curlew Sandpiper. Width of arrow indicates the percentage of movements in that direction (see inset). Green indicates tree cover.

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3.5 Mapping The newly created spatial layers illustrate the current knowledge about where birds roost and where they forage in close proximity to roosting sites (Figures 15a & b). A third layer was created to illustrate all potentially available intertidal foraging habitat (Figure 16) by modifying the existing Birds Australia shorebird feeding polygons. Pelican Island, which is a rocky island and sometimes has Ruddy Turnstone and Pacific Golden Plover roosting at high tide, was added to the roosting sites mapping (although it is not part of the BOCA Western Port Survey and was not visited during this study). Several other small sites (which are not currently counted) were also added as distinct roost sites, including Crawfish Rock, Chicory Lane reef, Mickâ&#x20AC;&#x2122;s Beach and Spit Point.

Some sites are rarely or no longer counted during the BOCA Western Port Survey (Queensferry, Hastings, Churchill Island, Dwyers Swamp, Corinella and Newhaven) and are therefore unmapped due to their low importance for shorebirds at present and the paucity of information about their spatial extent and how that may have changed over time. Similarly, a lack of information about the spatial extent of waterbird use at Tooradin also precluded the production of a map for this site.

Intertidal areas that may be of importance to foraging waterbirds in the north-eastern part of the bay are absent for similar reasons (i.e. lack of information).

Detailed maps for each site are provided in Appendix 2.

Figure 14. Red-necked Stint, the most common shorebird in Western Port.

Photographer P. Menkhorst

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Figure 15a. New mapping of waterbird habitat use in Western Port: high-tide sites.

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Figure 15b. New mapping of waterbird habitat use in Western Port: important foraging areas

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Figure 16. New mapping showing all available habitat for waterbird roosting, foraging or breeding.

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Western Port Welcomes Waterbirds: Waterbird usage of Western Port

3.6 Climate change risk Climate change risks associated with rising sea levels is greatest for shorebirds whose distribution is dictated by the availability of high-tide roosts. The coastal high-tide roosting sites identified and mapped in this report (excluding Bullock and Decoy swamps) comprise a total area of 248.7 ha or 2.5 km2. Collectively, these roost sites constitute approximately 0.35% of the total area of Western Port Bay. For the purposes of the sea level rise risk assessment, Pelican Island (see relevant map in Appendix 2) was removed because it is not currently part of the BOCA Western Port Survey and there insufficient count or observational data available to determine their relative importance to shorebirds (done for other sites, see Figure 16). With the removal of this site, the total area of the high-tide sites was 241.0 ha.

30

25

RAMS

High importance

Number of species

OBS

20

SPHI BGP

BARR PION

SETRD Moderate importance

WARN

HAST

10

QUEEN CHUR DWY

0 1.5

TORT FAIR

LONG

15

5

BRYC REEF

Low importance â&#x20AC;&#x201C; not mapped and sea level rise risk not assessed

TOOR

NEW

2.5

3.5

4.5

5.5

6.5

Log(abundance)

Figure 17. Importance of each site for shorebirds (Australasian and Holarctic).

See Appendix 1 for site abbreviations.

A substantial proportion of the area of the high-tide sites was under 1.5 m AHD (92.59% or 223.2 ha), meaning that on a current high tide of 1.5 m AHD or higher (which is approximately equivalent to 3 m above (tidal) Prediction Datum), only 7.41% of the roosting network is available for waterbird use. The total area of the high-tide sites between 1.5 and 2.5 m AHD was 17.4 ha or 7.24% of the total. Based on the assumption that anything under 2.5 m AHD will be inundated with a 1 m sea level rise, the area unavailable to birds at the peak of high tide was calculated to be 240.6 ha or 99.83% of the total high-tide roost area. Thus, virtually the entire high-tide roosting network will be inundated on the highest tides with a 1 m sea level rise.

Of the 14 high-tide roosting sites for which this spatial analysis could be undertaken (including some no longer used regularly by birds but of historical importance), eight have limited or no hinterland (in the case of islands) available to allow for natural migration inland (based solely on area) (Table 7).

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Table 7. Summary of inundation risk for each mapped high-tide roost site, derived from GIS spatial analysis of LiDAR Digital Elevation Models (<2.5 m) and high-tide polygon shapefiles.

Site importance relates to use by shorebirds (Australasian and Holarctic) rather than all waterbirds, as these are the dominant species that rely on tidal habitats.

Site

Proportion inundated at high tide (<2.5 m AHD) 99.97%

Likelihood of shoreline migration inland

Low Sandy spit on main point may erode or shift but most of bay shoreline retreat restricted by levee banks.

Mangroves may facilitate sediment accumulation

high

Barrallier Island/ Chicory Lane reef

100.00%

Low Both the island and the rocky reef will be entirely inundated

high

Bunyip River/Yallock Creek

99.90%

Moderate–high Shoreline retreat through erosion into farmland possible Mangroves may facilitate sediment build-up

high

Reef Island

99.84%

Moderate–high Majority of island will be inundated shoreline in Bass Bay may retreat into saltmarsh and onto farmland behind marshes

high

Fairhaven, French Island (incl. Tankerton jetty)

99.96%

Low–moderate Shoreline may retreat in some places into saltmarsh but down-shore erosion may counteract migration

high

Tortoise Head

100.00%

None Rocky ridge behind prevents migration

high

Observation Point/ Ghetto Rocks/ Rhyll Inlet

99.63%

Low Most of point and inlet will be inundated Shoreline retreat restricted by urban development

high

Sandy Point

98.66%

Moderate Some shoreline retreat possible through erosion Sediment build-up possible

moderate

Warneet beach, channel & Long reef

100.00

Low–high Some urban development restricting shoreline retreat at Warneet Quail and Chinaman’s Islands likely to impacted Long reef will be inundated

moderate

Rams Island (incl. Bird Island & Peck Point)

100.00%

None Island sites will be entirely inundated Shoreline retreat through erosion possible

moderate

Long Island

100.00%

Moderate Island will be entirely inundated Saltmarsh landward of the island may allow for shoreline migration

moderate

Settlement Rd

97.74%

Low Levee banks prevent shoreline retreat No mangroves currently (or historically *) present along this shoreline

moderate

Blue Gum & Spit Points, French Island

98.40%

Moderate Shoreline retreat through erosion possible

Micks Beach

100.00%

Pioneer/Stockyard

High Saltmarsh in hinterland may allow for shoreline retreat †This site is no longer counted – its importance is historical in nature * see Bird (1986)

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Importance for shorebirds (see Figure 16)

moderate † (no data)

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3.7 Threats at key sites A list of potential threats that may affect major high-tide sites (and some other important sites) was compiled based on discussions with land managers and waterbird counters, and observations during field surveys. The most commonly identified threats in Western Port were: • Habitat loss and modification • Disturbance from beach users (walkers, joggers, dog walkers, etc.)

• Disturbance from water users (fishing, sailing, personal water craft and similar) • Nest loss (trampling, storm or tidal inundation) • Bird injury &/or mortality (predation, collision with vehicles or vessels, tangling in fishing line) • Competition • Aircraft activity, including microlights.

Table 8 lists potential threats at each site and includes the climate change inundation risk assessment results from Table 7.

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Table 8. A list of main threats operating at key waterbird sites in Western Port.

More details on land managers at each site can be found in State of Victoria (2003)

Major roost sites

Threats potentially impacting site

Source †

Stockyard Point (Jam Jerrup) remainder of Pioneer Bay

disturbance from beach users—fishers, walkers and their dogs fox predation erosion of sandy spit potential inundation risk

field obs.

Land manager DSE

Barrallier Island & Chicory Lane reef

disturbance from boat and PWC users (mooring in close proximity and landing) risk of oil spill impacts potential inundation risk

field obs.

PV

Bunyip River & Yallock Creek

disturbance from increased use of Tooradin airport changes to grazing regimes predation by foxes potential inundation risk

field obs.

PV (foreshore) private (hinterland)

Reef Island & Bass Bay

disturbance by fishers & horse riding Black Rat and fox predation potential inundation risk

PV PINP

PV

Tortoise Head

disturbance from boat users (mooring in close proximity and landing) risk of oil spill impacts potential predation by cats potential inundation and storm surge risk

PV

PV

Sandy Point/Hanns Inlet

erosion of sandy spit potential inundation risk

Fairhaven/Chilcott Rocks

disturbance from walkers erosion of beach risk of oil spill impacts potential inundation risk

PV field obs.

PV

Observation Point/Ghetto Rocks/Rhyll Inlet

disturbance from beach users – fishers, bait collectors, walkers, joggers and dog owners disturbance from boat and PWC users particularly jet skis (mooring in close proximity and landing) predation of breeding birds by cats and foxes potential inundation risk

PINP field obs.

PINP

Rams Island (incl. Bird Island)

potential disturbance from boat users storm surge risk potential inundation risk potential predation by cats weed invasion

PV Quinn & Lacey (1999)

PV

Settlement Road

potential inundation risk

Long Island

geomorphological change due to Port development erosion of sandy spit potential inundation risk potential inundation risk disturbance from water users in transit domestic dogs chasing birds (Warneet boat ramp) risk of oil spill impacts

Blue Gum Point Warneet & channel Long reef

DOD

PV DSE

field obs.

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PV DSE

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Major roost sites

Threats potentially impacting site

Source †

Land manager

potential disturbance from water users potential inundation risk Tooradin

all except risk of oil spill impacts

DSE/PV

Queensferry

potential disturbance from beach and water users

Hastings

all

MPS

Churchill Island

disturbance from beach and water users (cat and fox free at present)

PINP

Newhaven

disturbance from beach and water users predation of breeding birds by dogs, cats and foxes coastal development

BCS

Mick’s beach

risk of oil spill impacts potential predation by cats potential inundation

PV

PV

† source of information where available through anecdotal/unpublished accounts and discussion with stakeholders, or observations made during field surveys other abbreviations are: PINP=Phillip Island Nature Park, DOD=Department of Defence, MPS=Mornington Peninsula Shire, BCS=Bass Coast Shire, PWC = Personal Water Craft

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4 Discussion Waterbird numbers in Western Port have declined significantly since the commencement of the BOCA Western Port Survey in 1973. These declines have involved the majority of waterbird groups (guilds) that occur in Western Port. Statistically significant declines were detected in 17 species from seven guildsâ&#x20AC;&#x201D;two ducks, four fishers, one grebe, one gull, two large wading birds, two resident shorebirds and five migratory shorebirds. Only two species of migratory shorebird (Red-necked Stint and Whimbrel) and one resident shorebird (Australian Pied Oystercatcher) showed an increase over the same period. This is of considerable concern as it suggests either that the drivers of change are locally widespread, affecting many species, or that a number of extrinsic and intrinsic detrimental changes are simultaneously occurring at different spatial and temporal scales.

Both scenarios are equally gloomyâ&#x20AC;&#x201D;the former has implications for Western Port ecosystem functioning, which may have flow-on effects to productivity and ultimately, anthropogenic values like the provision of food and recreation. The latter has profound implications for waterbird conservation, as it suggests a shift in the distribution of many species or a decrease in population sizes. Both may be indicative of habitat loss elsewhere in Australia and overseas.

4.1 What influences waterbird population dynamics in Western Port?

Several environmental/biological factors were found to significantly co-vary with counts of a number of waterbird species. These were commercial fish catch, rainfall in Western Victoria and streamflow rates from the Darling River. It was clear from these results that factors which influence populations of waterbirds in Western Port are either unquantified or are extrinsic and dispersed, varying across time and space in a manner which is difficult to measure or subtle in its influence.

4.1.1

Changes in local fisheries

Commercial fish catches varied significantly with counts of several fish-eating and shorebird species. Variation with counts of fish-eating birds was not unexpected, although these commercial species are not necessarily preferred dietary items (Trayler et al. 1989). Links between declines in populations of cormorants and fish availability are not a new concept and had been inferred in the past (e.g. Loyn, et al. 2001, BOCA 2003). This effect is thought to be more pronounced in shallow waters dominated by seagrass beds, which are nurseries and refuges for fish (Shapiro 1975, Pollard 1984, Hindell 2006).

Our analysis suggests that changes in the populations of Yellow-eyed Mullet Aldrichetta forsteri, King George Whiting Sillaginodes punctata, or Southern Sea Garfish Hyporhamphus melanochir will potentially have direct impacts on some cormorant species. Small fishes are more abundant in seagrass than in unvegetated habitats, but relatively few of these are juveniles of commercially fished species (Edgar and Shaw 1995). While cormorants may or may not be feeding on these commercial species, trends in commercial stocks may reflect broader trends in other fish of similar size or with similar life history strategies.

Pied, Little Pied and Little Black Cormorants feed on a variety of slow-swimming, benthic-feeding teleosts (bony fish) and crustaceans (Trayler et al. 1989; Marchant and Higgins 1990), and the smaller cormorant species tend to forage in shallow waters (Trayler et al. 1989). Great, Pied and Little Pied Cormorants have been recorded in relatively higher numbers in the shallow eastern and northern arms of Western Port, compared with the deeper western arm (Dann et al. 2003). This pattern was also observed on field surveys during this project, with birds often noted foraging over large mud banks like Middle Spit at high tide. Cormorants are also found foraging in association with seagrass beds (dependent on the presence of predators) in other regions in Australia (Heithaus 2005). Therefore, indirect changes in fish populations through impacts on seagrass may have

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equivalent effects on fish-eating birds as direct changes through reduction in prey availability.

Current data do not allow us to distinguish these possibilities. However, it seems likely that fish, cormorants and other waterbirds would all benefit from measures to restore seagrass beds and further regulate the harvest of fish by commercial and recreational fishers.

The extent to which changes in fish availability influence Caspian Tern was less clear as the effect was masked by a simultaneous influence of inland water availability. This influence of inland water availability may also apply to the cormorant species discussed above, although this was not evident in the modelling results. Cormorants breed in varying numbers at inland and coastal sites (Marchant and Higgins 1990), and the two black species breed primarily inland and are absent from Western Port when there is plentiful water inland (Loyn et al. 1994). Caspian Terns may also move inland at such times, as well as moving along coasts or to Bass Strait islands (Higgins and Davies 1996). Historic breeding records exist for Little Pied and Pied Cormorants on French Island (Loyn 1978, Quinn and Lacey 1999) and for Little Pied Cormorant on Phillip Island and the mainland at Coolart Wetlands (Loyn 1978, BOCA 2003, B. Thomas pers. comm.). Caspian Terns breed locally as single pairs and the nearest substantial breeding colony is on Mud Islands in Port Phillip Bay (Menkhorst 2010).

Significant declines were detected in both Great Cormorant and Little Pied Cormorant, and were matched by simultaneous declines in fish catches. This finding supports the hypothesis of real declines in both birds and fish rather than reduction in reportable fish take due to licence buybacks.

Seagrass losses throughout the bay, but especially in the north-east, were substantial in the late 1970s and early 1980s (Blake and Ball 2001) and have been implicated in the changes in aquatic and semi-aquatic biota that make use of seagrass habitat (Shapiro 1975, Bulthuis et al. 1984). Total commercial catches (all fish species) started declining around the start of the 1990s (DPI 2008), a difference of 4â&#x20AC;&#x201C;5 years, which is only slightly longer than the minimum age to recruitment of the fish species investigated in this study. This suggests that declines in commercial fisheries can be attributed to losses of seagrass, resulting in declines in these cormorant species. However, seagrass recovery in the late nineties was not coupled with a subsequent increase in fish catches, which may be due to the commencement of commercial license buybacks in 1999, that is, reduced fishing effort (D. Ball pers. comm.). Nevertheless, the possibility that over-fishing (both commercial and recreational) has indirectly contributed to cormorant declines cannot be ruled out.

There was a significant correlation between commercial fish catches and counts of four shorebird species (Common Greenshank, Eastern Curlew, Grey-tailed Tattler and Whimbrel). In Victoria, fish constitute a large proportion of the diet of Common Greenshank (D. Rogers pers. comm.).

However, Grey-tailed Tattler feed on small fish only rarely, and fish do not usually form part of the diet of Eastern Curlew and Whimbrel (Dann 1993, Higgins and Davies 1996, Finn et al. 2008).

In Western Port, Whimbrel feed preferentially on crustaceans on mudflats with between 10 and 50% seagrass cover, and usually away from the waterâ&#x20AC;&#x2122;s edge (Dann 1993). Prior to the midnineties, fish catch was relatively stable and Whimbrel numbers increased to a peak around 1995 followed by a decline in subsequent years. That decline matches the decline in fish catch but also reductions in rainfall from the mid-nineties. Increased dryness associated with drought conditions could impact on seagrass beds exposed at low tide, potentially having flow-on effects to both fish and Whimbrel foraging success. Similarly, both Grey-tailed Tattler and Common Greenshank feed on invertebrates and occasionally small fish (Higgins and Davies 1996), meaning that they will also be subject to possible climate impacts on seagrass and changes in fish availability.

In Moreton Bay (Queensland), Eastern Curlew distribution on tidal flats is most strongly related to sediment resistance, which dictates prey availability (Finn et al. 2008). However, variation in substrates (mud, sand or seagrass) was not a strong factor influencing their distribution, although a slight preference for sandy substrates was noted (Finn et al. 2007). Given this factor in isolation,

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the relationship with fish and the role of seagrass in Eastern Curlew population distribution is unclear. However, Ghost Shrimp are a key dietary item for curlew and shrimp may respond to similar environmental factors as small fish (D. Rogers pers. comm.). Thus, ghost shrimp population increases or decreases may positively correlate with changes in fish populations, resulting in the significant correlation between fish and curlew detected here. Data on benthic prey abundance would be necessary to explore these patterns further.

Overall, the significant relationship between trends in these four shorebird species and commercial fish catch supports the notion that changes in seagrass habitat may have indirect effects on other organisms as well as fish, even those that are not obligate users of seagrass.

Commercial fishing has been closed in Western Port since 2007 but it is probably too early to detect any population response in commercial fish species or in fish-eating birds. However, there seems little reason to anticipate a reversal of the decline in fish-eating birds because the effects of past seagrass losses combined with increasing recreational fishing pressure (with increases in Melbourneâ&#x20AC;&#x2122;s population and visitation by anglers) has probably had a greater effect on recruitment to fish populations, over-riding any effect of closing the commercial fishery. Thus, we can be reasonably confident that impacts on fish, even those that are not targeted for fish-harvesting, are going to have flow-on impacts to several cormorant and tern species.

4.1.2

Reduced rainfall and water availability

Two declining waterbird species Australian Shelduck and White-faced Heron, appeared to have experienced the sharpest fall in numbers between the early nineties and 2009, coinciding with the most recent years of reduced rainfall (1997â&#x20AC;&#x201C;2009). In addition, six other species (Chestnut Teal, Common Greenshank, Fairy Tern, Pacific Black Duck, Royal Spoonbill and Ruddy Turnstone) showed a downward trend over the same time period. Although this was not formally tested, it suggests that changes associated with reduced rainfall may be having a broader effect. In support of this notion, Australian Shelduck trends were found to be significantly influenced by rainfall patterns in Western Victoria, although the nature of that relationship was complicated by seasonal variations.

Correlations with annual rainfall indices for southern and eastern Australia have been previously found for Little Pied Cormorant, White-faced Heron, Chestnut Teal, pelicans and swans (Loyn et al. 1994, Chambers and Loyn 2006). In this investigation, only a single species of duck (Australian Shelduck) and one tern species (Caspian Tern) were influenced by changes in rainfall elsewhere (in the latter case, Darling River streamflow). Shelduck are widespread across Victoria and are one of the most numerous ducks on south-west Victorian wetlands (Emison et al. 1987, Summer Waterfowl Count data (DSE), authors pers. obs.). Shelduck may have shifted their distribution in response to changes in regional climate, using Western Port in exceptionally dry seasons as a drought refuge. However, if this were the case, numbers of shelduck should have increased through the period of reduced rainfall, which was not the case. Alternatively, shelduck may have experienced reduced breeding success due to a lack of suitable wetland habitat after prolonged periods of drying.

Caspian Terns are commonly reported from inland waterways and waterbodies (Barrett et al. 2003, Higgins and Davies 1996). This species is quite mobile and probably responds readily to changes in wetland availability, which is known to be an important driver of waterbird population change, and will correspond approximately to streamflow patterns (Loyn et al. 1994). Seasonal and annual movement in response to inland water availability has been the subject of investigation previously (Chambers and Loyn 2006), and the trends observed here adds further support to the notion that Western Port is an important drought refuge for many species. Furthermore, it is also seasonally important for both visiting and breeding non-migratory waterbirds.

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4.2 What are the causes of waterbird declines?

Of the 37 waterbird species for which adequate count data exist, 16 were found to have significantly declined over the course of the BOCA Western Port Survey. The probable cause of some of these declines has been previously discussed in the context of fish, seagrass cover and water availability. However, for the majority of these species, there are no obvious biological or environmental factors for which adequate data was available, which could be tested to explore possible causal relationships.

Of the guilds that contained declining species, Holarctic shorebirds had one of the largest proportions of species in decline. This is consistent with declines in shorebirds elsewhere in the East Asianâ&#x20AC;&#x201C;Australasian Flyway (Gosbell and Clemens 2006, Nebel et al. 2008, Amano et al.

2010, Wilson et al. 2011). Evidence is accumulating that rapid loss of intertidal habitat at staging sites in the Yellow Sea may be the primary cause of declines (Amano et al. 2010, Rogers et al.

2010b). Despite international bi-lateral agreements between Australia and several Asian nations on the protection of migratory shorebirds (CAMBA, JAMBA and ROKAMBA), important intertidal habitat continues to be destroyed to meet increasing demands associated with industrial development (Inglis and Rogers 2010, Lewis and Russell-French 2011).

Therefore, the protection of migratory shorebirds visiting south-eastern Australia will require activities and social/environmental changes beyond the geographic boundaries of the Western Port catchment, and, in some cases, beyond Australia. However, it is critical that shorebird habitat in Western Port is protected and carefully managed as survival of migrants (which still arrive in summer in large numbers) and local species is reliant upon the quality of these foraging and roosting areas. This is reflected in declines detected in non-migratory species and indicates that potentially chronic and widespread problems are also occurring locally.

Identifying the causes of declines in ducks and large wading birds is complicated by the erratic nature of their movements in response to inland water availability (Kingsford and Norman 2002, Roshier 2006). Movement in response to water availability was supported by some of the modelling results and previous studies, which indicated changes in populations of several species concurrent with rainfall and climate patterns (Dann et al. 1994, Loyn et al. 1994, Chambers and Loyn 2006). However, changes in some species such as Grey Teal and Australian White Ibis, could not be accounted for with the data used in this study.

Grey Teal have been found previously to respond to inland water (Chambers and Loyn 2006), which is likely to be the case here despite the inconclusive modelling results using rainfall covariates. In contrast, changes in Australian White Ibis have not been subject to previous investigation with the exception of BOCA (2003), where ibis were noted to decline locally in dry years. Local anecdotal reports of an apparent displacement of Australian White Ibis by Strawnecked Ibis in terrestrial areas where Australian White Ibis used to feed in large numbers may explain the changes in ibis numbers. This is also supported by diminished ibis breeding on French Island and at Coolart Wetlands on the Mornington Peninsulas well as changes in breeding recorded on Mud Islands, Port Phillip, whereby Straw-necked Ibis have taken over as the dominant breeding species (Menkhorst 2010).

It is plausible that the gross estimates of inland water availability used in this study are not adequately sophisticated or targeted to detect the role of inland water events in determining the annual distribution of several waterbird species. A quantitative measure of seasonal and annual wetland availability (in terms of area and depth) from non-coastal Victorian regions (and elsewhere) would be highly informative.

It is clear that some local changes have occurred that are affecting resident species. Both Masked Lapwing and Red-capped Plover were found to have declined. These are widespread species that nest on grass (including pasture and lawns) and sandy shores or sparse saltmarsh, respectively. The

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causes of their decline are not known, but a contributing factor is likely to be the presence of many introduced predators (Red Fox Vulpes vulpes, Cat Felis catus, Black Rat Rattus rattus, domestic Dog Canis familiaris) in addition to natural nest and chick predators (ravens, birds of prey, gulls).

Fox predation has been implicated in the population declines of Masked Lapwings. Recent data on lapwing densities on Phillip Island found them to have significantly increased over a five year period from 4.6 to 7.1 birds/km2, coinciding with a fox eradication program over the same time period (S. Murphy unpubl. data). A comparison between counts on the island and the adjacent mainland at the end of that period showed between six and eleven times more birds on the island (S. Murphy unpubl. data), further suggesting that fox numbers may be contributing to lapwing population declines. It is unclear what may have contributed to the decline in Silver Gulls, but it is possible that closures of coastal rubbish dumps may have driven shifts in local populations to areas outside Western Port.

4.3 Important areas for waterbirds in Western Port A simple ranking procedure was used to explore the relative ‘importance’ of each count site for waterbirds. The most striking outcome from this exercise was the sites which frequently ranked highly: Pioneer Bay (including Stockyard Point and GMH drain), Barrallier Island and north-west French Island, and Bunyip River/Yallock Creek. This is particularly notable in the summer months (late November through to early February) and is driven by the disproportionately high numbers of migratory shorebirds that are recorded at these sites.

4.3.1

Habitat use by shorebird species

Shorebirds were found to occur most frequently in close association with two main features of Western Port: extensive intertidal mudflats with a sparse to dense cover of seagrass (Zostera/Heterozostera species) but occasionally with no seagrass, and nearby exposed high-tide roost sites (islands, sandy spits, rocky reefs and beaches with low fringing vegetation). Shorebirds rely almost exclusively on exposed or slightly submerged intertidal mudflats for foraging and use nearby high-tide roost sites when mudflats are inundated. They generally prefer open areas for roosting where their view is not obscured (a predator-avoidance measure). Tall vegetation near potential roosting or foraging areas will usually discourage use of those areas. Thus, suitable shorebird habitat is defined by the presence of exposed tidal mudflats in relatively close proximity to exposed (open) high-tide roosts.

Collectively, coastal high-tide roost sites constitute less than half a percent of the area of Western Port Bay. Non-coastal sites like swamps and nearby paddocks may be used intermittently as roosting habitat by shorebirds, e.g. Bullock Swamp, marshy pasture near Heifer Swamp, and pasture near Settlement Road. However, sites like these are also restricted in area (e.g. Bullock Swamp, which is a large natural terrestrial wetland, is less than six hectares in total area) and subject to other potential threats like removal of livestock grazing (which keeps vegetation low).

Furthermore, swamp habitats like those on French Island may not be available for extended periods in dry years, which was the case for many years leading up to the increases in rainfall in 2009. Therefore, the protection of the coastal high-tide roost network is of utmost importance.

The greatest and most consistent concentrations of shorebirds at high tide were in the north and east of the bay. Less consistent but still high in importance were Tortoise Head (very important in early years of the BOCA Western Port Survey), Observation Point and Reef Island in the south.

Collectively, these two groupings of high-tide roosts (Pioneer/Stockyard–Bunyip/Yallock– Barrallier and Tortoise Head–Observation Point–Rams Island–Reef Island) form triangles encompassing probably the most productive regions of the bay (in terms of primary productivity; see Shapiro 1975).

Taking all Red-necked Stint, Curlew Sandpiper and Bar-tailed Godwit movement data together, Bar-tailed Godwit appeared to be the most likely to make local movements, with nearly 40% of

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recaptures being away from the banding site. The two smaller species were progressively more site faithful, which may be a reflection of the age structure of each species (i.e. a greater proportion of juvenile godwits were recaptured than stints or sandpipers), as juveniles are considered less site faithful than adults (D. Rogers pers. comm.). It may also reflect the choice of capture sites— chosen because of the high numbers of Red-necked Stints regularly found there, so they may not be optimal roosting sites for the Bar-tailed Godwit.

Red-necked Stint and Curlew Sandpiper were found to make use of several high-tide roosts in a single non-breeding season, although movements represent only a small proportion of these species (7.5% and 5.9%, respectively). Movements inferred from recaptures of banded adult birds indicated that a small number of birds moved fairly regularly between Barrallier Island, Yallock Creek and Stockyard Point in the north-east part of the bay. Bi-directional exchange of birds of both species appears to occur mostly between Yallock Creek and Stockyard Point, whereas exchange between Yallock Creek and Barrallier Island was generally undertaken only by stints..

Yallock Creek is known to be an important roost for small shorebirds and is therefore frequently targeted for cannon-netting activities. It is possible that frequent catch efforts at this site may bias recaptures or miss opportunities elsewhere. In order to reduce bias from recapture avoidance behaviour, any birds recaptured within 48 hours were excluded from the analyses. Thus the movement patterns inferred here correspond to periods of time from several days to several months. Regular movement between Yallock Creek and Barrallier Island has been inferred previously (Shapiro 1975) and exchange between the three sites has also been detected during cannon-netting activities (C. Minton pers. comm.). Thus, these patterns are likely to represent roost site choices by birds rather than recapture avoidance behaviour.

There are few other sites that regularly contain large numbers of shorebirds that may be overlooked. One exception is the Chicory Lane reef to the immediate east of Barrallier Island, which is often used by birds as a pre-roost, or as an alternative roost to Barrallier Island on neap tides. The possibility that birds have re-commenced using Settlement Rd in recent years cannot be ignored, and this site has previously been considered as part of a single complex that includes Yallock Creek and Bunyip River (Shapiro 1975). Birds have also been found using a small roost on the north-west tip of French Island (Mick’s Beach). Each of these sites falls within the movement ‘triangle’ illustrated in Figure 12 and are probably regularly used as intervening roost sites in this region of Western Port. Similarly, Spit Point and Duck Splash (north-east French Island) may serve as an alternative roost sites when conditions are suitable (e.g. some exposed but wet mud in Duck Splash).

Given the pattern of movements found over many years of shorebird study, it is reasonable to assume that birds make regular use of a network of high-tide roosts. Curlew Sandpipers are known to be reasonably site faithful in their Victorian non-breeding range (Minton et al. 2006). Their use of these sites interchangeably would suggest, in the context of site faithfulness, that the three locations actually constitute a single ‘site’ for this species, and possibly for Red-necked Stints also.

This contrasts with resident shorebird species like the Australian Pied Oystercatcher, which is known to be very site faithful from season-to-season and year-to-year (inferred from re-sightings of colour-banded birds: R. Jessop, unpubl. data). This seems to be particularly true of birds originally caught at Stockyard Point and Fairhaven, which are frequently re-sighted at the same site. Movement away from Fairhaven seems more likely between years rather than within (R. Jessop, unpubl. data), which may reflect dispersal of non-breeding birds.

Two other migratory shorebird species have been found to move between roost sites over larger distances, using them as alternative roosts at different times during the non-breeding season.

Observations made at cannon-netting sites by VWSG members have indicated that Bar-tailed Godwit using Observation Pt (which is a regular site for this species) extend their non-breeding ‘home range’ to include The Gurdies and Stockyard Point (Pioneer Bay), which they may use for

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several weeks (C. Minton pers. comm.). Similarly, Eastern Curlew are occasionally observed moving between Pioneer Bay and Yallock Creek/Settlement Road. A small number of withinseason recaptures have confirmed these observations (C. Minton pers. comm.). It is probable that curlews using these sites are the same birds that use Barrallier Island and Chicory Lane reef to the east as a roost site on neap tides (C. Minton pers. comm.).

The daily or weekly choice of roost by shorebirds will depend on a number of factors including prevailing weather conditions (wind direction and speed, and precipitation) and tide height, with some sites being unsuitable in windy and rough conditions and others unsuitable on very high tides. Proximity of roosts to productive benthic foraging areas is particularly important, and changes in prey availability may cause birds to alter their choice of roost (Rogers et al. 2010a, Rogers et al. 2011). In recent years, Australian Pied Oystercatcher numbers have increased in the western region of the bay, and simultaneously decreased in previously important areas like Pioneer Bay (C. Minton pers. comm., this study). This shift may be related to reduced abundance or quality of prey in eastern regions of the bay, and/or an increase in the abundance of prey in the western region (C. Minton pers. comm.). Given this variability in use of roosts, it is important to maintain and protect sites in unison for the obvious collective value they have to flocks of shorebirds throughout their non-breeding season. Loss of roost sites from this network will concentrate birds into fewer areas, which could contribute to higher disturbance and predation risk, as well as increasing the likelihood that birds are exposed to inclement weather conditions.

The interchangeable use by shorebirds of several high-tide roost sites in the eastern and northeastern regions of Western Port increases the need to consider the function and management of intervening intertidal areas. Shorebirds tend to feed in close proximity to their preferred roost site, to reduce energy used in travelling between foraging and roosting sites every tidal cycle (Geering et al. 2007, Rogers et al. 2011). Knowledge about the use and importance of mudflats in this part of the bay is lacking, largely due to the logistical difficulties in accessing these areas. In this area, most of the mudflats (bar those at the extreme edges of the North Arm) are less than 1.5 m above mean low water mark (Shapiro 1975) and will therefore be exposed for a shorter time than other parts of the bay. Seagrass beds, which appear to be important as foraging substrate for shorebirds, are distantly located from several main roost sites (Figure 18). The manner in which predicted sea level rises associated with climate change affects low-lying intertidal areas may be critical to how birds use this part of the bay in future, and may ultimately influence their choice of roost site.

Several intertidal areas have been previously identified as being potentially very important to foraging waterbirds. These are the far eastern low-tide mudbanks of the North Arm (between the lower Bouchier and Horseshoe channels), the western Tooradin tidal flats (between the lower Tooradin and Gentle Annie channels), Middle Spit mud banks, the eastern Tortoise Head tidal flats, the southern end of Hanns Inlet and the Barrallier Island/ north-west French Island tidal flats (Shapiro 1975). These locations were identified on the basis of their height above mean low water mark, meaning that they are exposed for longer than other tidal flats between high tides. The Tortoise Head tidal flats (and saltmarshes) have been identified during past studies as being important for shorebirds (Loyn 1978, Quinn and Lacey 1999).

This study has confirmed the importance of Middle Spit mud banks, Barrallier Island tidal flats and the western Tooradin tidal flats. It has also identified Watson Inlet as an important foraging and roosting area for large wading birds and some migratory shorebirds (e.g. Common Greenshank). However, no survey work has been undertaken on the eastern tidal flats to confirm their current usage. This gap needs to be addressed, especially given the potential importance of these areas as intervening foraging habitat for shorebirds roosting at Stockyard Point, Yallock Creek and Barrallier Island. With sea level rises, their importance will increase, especially if mud accretion elsewhere is hindered by other processes, for example, altered sediment dynamics due to changes in coastal geomorphology (coastal development) or channel morphology.

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Figure 18. Aerial image of Western Port showing the current distribution of seagrass beds (green shading) with respect to high-tide roosts (in red).

4.3.2

Habitat use by other waterbird species

Other waterbirds are generally less restricted by their habitat requirements. Ducks and Black Swan will use a variety of open habitats like flooded saltmarsh, fresh waterbodies and intertidal mudflats where they can forage, either on the surface or by diving (Loyn et al. 1994). They can either roost on shore (e.g. swans use mangrove edges and mudflats), or while floating on open water (Loyn et al. 1994). In addition, Black Swan is a herbivore, foraging in seagrass beds within Western Port (Dann 2000). Consistent with these broader habitat requirements, ducks were found in their largest numbers at GMH drain, Bunyip/Yallock Creek and north-west French Island, and the Black Swan was most plentiful at Reef Island (which also incorporates the Bass Bay area), Fairhaven to northwest French Island, and Tortoise Head. Collectively, these areas provide the full suite of habitats required for these species to forage, rest and in some cases, breed.

Cormorants and other fishers are similarly unconstrained by tidal cycles and geomorphology of the coastline, and are found in most places where there is water of suitable depth to allow fishing (typically less than several metres), and where there are exposed natural or artificial structures exist upon which they can roost. Thus, fishers tended to be more evenly distributed around the bay than other multi-species guilds, with the largest numbers occurring at Observation Point and Barrallier Island.

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Large wading birds make use of most available habitats, except for deep open water. Consistent with this, they were found in their highest numbers at north-west French Island high-tide sites, which has intertidal mudflats, saltmarsh, wetlands and mangrove habitats. Intertidal mudflats are particularly important to these species during summer and early autumn, when nearby nonestuarine water sources are scarce and pastures are dry (Lowe 1981). In the early years of the survey, Churchill Island tidal flats, Hastings Bight, Watson Inlet (Yaringa) and the western end of Tooradin tidal flats were found to hold the greatest foraging congregations of large wading birds (Lowe 1981). This distribution is likely to have shifted with loss of seagrass cover after that time, but no observations were made during this study that conflict with their earlier records, with the exception of numerous observations made of ibis, herons and spoonbills foraging on the Middle Spit mud banks at low tide. Coastal vegetation communities like mangroves and teatree scrub are frequently used by large wading birds for roosting. Thus, suitable habitat for the other waterbird groups is the suite of estuarine and coastal habitats from open channels and tidal flats to coastal vegetation and the adjacent hinterland.

4.3.3

Breeding sites

Limited observations were made on breeding during this study. Most were consistent with previous reports and studies on breeding. Terns (Caspian and Fairy) breed on some of the island sites (Rams Island and Reef Island, and Tortoise Head) and observations of nesting at those sites were also made during this study. Successful breeding of these species at these sites is highly variable. Chicks do not always hatch at Rams and Reef islands and breeding has not recommenced at Tortoise Head in recent years (Minton et al. 2009, 2010). Colonially breeding species remain absent from historic breeding sites on French Island.

During this study, annual rainfall returned to close to the long-term average after more than 12 years of well below average rainfall and wetlands that had been dry for many years were observed filling or filled. At least one of the major wetlands on French Island (Bullock swamp) has been slow to fill, which may indicate that groundwater, rather than runoff, is the dominant source of wetland water on French Island (D. Stephenson pers. comm.). Some wetlands which were full in late summer (2010â&#x20AC;&#x201C;2011) have since dropped in water level, and it appears that more rainfall is required to restore them to their former state (J. Malloy pers. comm.).

Species like Australian White Ibis will not breed until nesting trees are completely surrounded by water (Quinn and Lacey 1999). Therefore, French Island wetland sites should be monitored closely over the next two or three summers, especially if local climate conditions continue to be relatively wet. As Western Port used to be one the strongholds for breeding Australian White Ibis and Royal Spoonbill in southern Australia (Lowe 1981), re-commencement of breeding will be significant and should be carefully managed if and when it does occur. Critical to this will be to ensure that breeding colonies are not disturbed.

Water was present in the Cerberus settling ponds (which were dry for many years between 1997 and 2009) and ducks, grebes and swamphens were observed breeding there. Although by no means a significant event, it is nevertheless important that mainland waterbodies are being used for breeding as soon as they are suitable. Increasing human population pressure will almost certainly reduce successful mainland breeding events, due to increasing disturbance and predation by the species like cats and foxes, which follow urbanisation. This suggests that sites like Cerberus which are largely buffered from urban development by their land tenure will be increasingly important for locally breeding waterbirds.

Of interest is the increasing numbers of Cape Barren Geese residing and breeding within Western Port. Observations of many geese on French Island, Phillip Island and Churchill Island were made prior to and during this study. The role of this species in the Western Port ecosystem remains to be seen, but as a grazing species its ultimate population level will likely be determined by the

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availability of suitable pasture, and the tolerance of landholders to losing stock feed to this wild species (it was formerly considered a pest in parts of South Gippsland: Dorward et al. 1980).

Australian Pied Oystercatcher was the only resident shorebird species observed breeding during opportunistic surveys. Oystercatchers breed successfully in Western Port in contrast to other resident species like Masked Lapwing, Red-capped Plover and Hooded Plover, which are known to suffer from human disturbance and predation. Numbers of oystercatchers were found to have increased over time and, consistent with this trend, breeding pairs were observed on French Island each year. The presence of many juvenile birds in post-breeding flocks during this study was also indicative of successful breeding. Foxes have been implicated in reduced breeding success of oystercatchers elsewhere (Taylor et al. in press, C. Minton pers. comm., VWSG unpubl. data).

French Island is fox free, although there are many feral cats on the island (Johnston et al. in press) which are likely to prey upon some juvenile oystercatchers. Despite the presence of cats, it is clear that amongst its many natural values, French Island is an important site for resident ground-nesting birds.

4.4 What threats are operating at key sites?

A suite of threats are suspected to affect waterbird populations both in Western Port and elsewhere. These include disturbance, habitat loss, predation and climate change (sea level rise and increased storm surge activity). Unfortunately, quantitative information relating to these threats at key waterbird sites is lacking for Western Port. In lieu of such data, verbal accounts from local land managers and observations made by waterbird counters and during field surveys were compiled to produce a summary of the known or hypothesised key threats. Conversations with stakeholders and community members, and direct observation provided most information.

The most common perceived threats were disturbance to roosting and foraging birds from beach users and boat operators, and predation by cats, foxes and Black Rats. Some of these are already subject to local management (for example, Parks Victoria undertake Black Rat control on Reef Island and cat tracking and eradication on French Island). However, threats relating to disturbance are less easily addressed and rely on the enforcement of restrictions to access (Antos et al. 2007) and communication of the issue to members of the public (BOCA 2005, Williams et al. 2009).

Public perceptions of waterbirds and their habitats in Western Port was explored further in a parallel study on social perceptions to Western Port and the birds therein (Christie et al. 2010).

This study has identified a suite of issues relating to Western Port and birds, and highlighted a selection of communication methods that may be used to deliver conservation messages to community members and bay users. This is discussed in more detail below (management recommendations).

It was clear from anecdotal accounts that there is no information for Western Port about some threats that are known to be a problem elsewhere in Australia. Competition between humans and birds for resources like shellfish, bait fish and commercial fish has been implicated in oystercatchers declines in Tasmania (Taylor 2004), but the frequency of its occurrence in Western Port is undocumented. Furthermore, there is no regular or targeted monitoring of breeding success at key sites where waterbirds may breed from year-to-year, for example, French Island, Quail Island and Watson Inlet, Hanns Inlet or Bass Bay. The lack of targeted monitoring at breeding sites throughout Western Port means that it is difficult to track possible causes of shifts in breeding patterns by resident species. Thus, it is unclear how important current Western Port breeding sites are in a statewide context, which hinders development of strategies for their protection or augmentation.

Disturbance is likely to be one of the most widespread current and future threats to waterbirds.

This has been previously highlighted in numerous reports on Western Port (Shapiro 1975, Andrew et al. 1984, PPK 2000), as well as studies elsewhere in Victoria (Antos et al. 2007, Weston and

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Elgar 2007). Disturbance can be expected to intensify with human population increases, especially in the south-eastern Melbourne growth corridor. Buffer and exclusion zones have been recommended in various other contexts to reduce disturbance impacts on waterbirds (Andrew et al.

1984, BOCA 2005). Exclusion zones have been recently implemented for Observation Point by Phillip Island Nature Park, to reduce disturbance risk to shorebird and other waterbirds and to increase nesting success of some locally breeding species. French Island Marine National Park has a special protection area centred on Barrallier Island (Parks Victoria 2007), which has probably reduced disturbance to the roost there but has not stopped it (B. Hansen. pers. obs).

It was not possible to elucidate the proportion of important waterbird areas in the bay where disturbance has biologically significant impacts. For example, shorebird nest loss from predation and storm surge inundation occurs at Rams Island (Minton et al. 2009, M. Douglas pers.comm.), but it is not known how frequently people attempt to access the island using vessels. This may be important as excessive disturbance of breeding birds (mostly Fairy and Caspian Terns at this site) may reduce the capacity of these species to successfully raise young in the face of other threats. It will be critical to improve our understanding of the frequency and extent of these impacts as Western Port experiences greater pressure from an expanding human population.

4.5 Climate change risks The high-tide (roosting) sites identified in this report comprise a total area of just under 250 ha (although this may vary from year-to-year with changes in local geomorphology from shifting sediments). All high-tide roost sites had greater than 95% of their total area under 2.5 m AHD and are therefore expected to be almost entirely inundated with a sea level rise of 0.8 m.

Of these, virtually all are considered to have moderate to high importance to waterbirds, particularly to shorebirds at high tide. These sites were: • • • • • •

Stockyard Point and Pioneer Bay Barrallier Island/Chicory Lane reef Bunyip River/Yallock Creek Reef Island Tortoise Head Sandy Point

• Fairhaven • Observation Point/Rhyll Inlet • Rams Island • Settlement Road • Long Island • Mick’s Beach.

Of these sites, only a single site (Settlement Rd) has been relatively unused in recent years and, therefore, has not been counted. Mick’s Beach is the only site that has never been systematically counted, so its importance in the broader context of Western Port is unknown. It will be critical to protect all 12 sites from current threats as they are clearly important now for shorebirds and are highly likely to remain important in coming decades. Sea level rises will almost certainly impose another layer of threat to all these sites in future decades.

The ‘bath-tub’ approach to simulating inundation is simplistic and has drawbacks, including its lack of consideration of other important coastal processes that will almost certainly influence the way in which the shoreline responds to sea level rise. However, the application of more sophisticated models such as the Sea Level Affecting Marshes Model (SLAMM) requires further

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information on input variables including habitat type, slope, sedimentation, accretion and erosion rates, and the extent to which the affected area is protected by sea walls (Galbraith et al. 2005).

The collection of such data was beyond the scope of the present study.

In 2003, CSIRO published a report detailing sediment accumulation, redistribution and sources in Western Port (Wallbrink et al. 2003). That report found that wind and tidal currents drive finesediment transport in a clockwise direction, a finding which was also reported in the earlier Western Port Environmental Study (Shapiro 1975). There is a general north-west to south-east transport with fine-sediment accumulating between Jam Jerrup, Corinella, San Remo and Rhyll.

Sediment cores showed a sedimentation rate of up to 5 mm/year (Wallbrink et al. 2003). This sediment may contribute to future aggradation of mudflats, potentially mitigating mudflat inundation. However, if wind or wave energy increases, more fine-sediment may become mobilised and stay suspended longer, and possibly be removed from the Western Port system.

These considerations, along with those relating to coastal erosional processes, will need to be included in future analyses of climate change risk on waterbird habitat in Western Port.

The majority of these sites have limited capacity for shoreline retreat or migration inland, which would help retain important coastal habitats for waterbirds. In the case of Pioneer Bay/Stockyard Point, the most important waterbird site in Western Port, the presence of a levee bank encircling over two-thirds of the shoreline will prevent shoreline retreat. Similarly, intermittent levee banks from Bunyip River around to Settlement Road will have a similar affect, although Yallock Creek is less restricted and migration of saltmarsh into pastures is not currently hindered by artificial geomorphic structures.

All island sites will be almost entirely inundated. As each island has only a very small proportion of its total area above high-tide line (collectively 5%), the longevity of island sites with sea level rise is very uncertain. Tortoise Head and Corinella (the latter not currently an important roost site but used intermittently by iconic species such as Whimbrel) are rocky headlands with rocky reefs and have no capacity for geomorphic change that will retain high-tide roost sites.

Observation Point, Stockyard Point, Sandy Point and various smaller points on French Island like Spit Point are, by virtue of their predominantly sandy substrates, quite mobile and may either shift position or erode away altogether, depending on the dominant hydrologic flow paths in the local area. Similar patterns may be observed with the sandy spits associated with Barrallier and Long Islands. Given the uncertainty surrounding the likely changes at each site with sea level rise it will be important to monitor shoreline changes from year-to-year and relate those changes to patterns of use by waterbirds. Protection of these sites from other threats will be absolutely critical.

In addition to this preliminary inundation risk assessment for high-tide roosts, there are areas of intertidal foraging habitat that will also require a similar assessment. For example, Middle Spit mud banks are completely inundated at high tide and partially inundated on high low tides, meaning that they will in theory, be lost completely with a 0.8 m sea level rise. This site appears to be important as both foraging and roosting habitat for many waterbird species, including Black Swan, ibis, White-faced Heron, Silver Gull, Pacific Gull, oystercatchers, Eastern Curlew, Whimbrel, Curlew Sandpiper and Red-necked Stint.

Similarly, intertidal mudflats around north-west French Island and Barrallier Island, southern French Island, Hastings, Rhyll and Bass River estuary may be subject to significant loss through inundation. Detailed bay-wide bathymetric data used in combination with bay-wide daily tidal exposure information are required to make a more detailed assessment of these areas. In order to make accurate predictions, information about projected sediment and hydrodynamics in the bay will be required to determine which areas evolve and which will be lost. This may require a sophisticated modelling approach which is beyond the scope of this project.

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4.6 Management recommendations Recommendations for future management fall under several themes. The first is the maintenance of habitat values at the key roosting and foraging sites identified in this study, the second is ecological monitoring and evaluation, and the third is communication and messaging.

4.6.1

Key roosting and foraging sites

The roosting sites identified in Figures 6 and 7 (for all waterbirds) and Figure 16 (for shorebirds only) as being of high and moderate importance must be protected and their habitat values maintained as far as possible (the threat of sea level rise is a particularly intractable issue). For shorebirds, in particular, this means limiting disturbance by humans and their companion animals, maintaining an open field of view (i.e. management of encroaching vegetation), and further investigation of options for adaptation to sea level rise. It is important to note that the significance of sites may vary over time as climate fluctuates (e.g. the wet–dry cycle), climate changes and habitat changes through other causes. Therefore, sites that ranked low in importance during the study period should not be neglected because their importance could rise as the habitat quality of the currently important sites fluctuates.

4.6.2

Ecological monitoring and evaluation

One of the strongest and most consistent themes to emerge from this and other environmental studies is the need to maintain or initiate ongoing monitoring. In particular, it will be important to continue the current waterbird monitoring, using comparable methods, including at the ‘inland’ wetland sites. Ongoing monitoring will be essential to elucidate the level of influence of changes from El Niño to La Niña events and the impacts of a changing climate on waterbird populations. In the context of this study, there were a number of sub-themes that emerged as matters requiring additional monitoring. These were survey sites, seagrass and its associated biota, and hydrodynamic modelling of intertidal mudflat availability.

4.6.2.1

Survey sites

In order to address conservation priorities in relation to waterbirds in the Western Port Ramsar site, there are a number of areas that should be targeted for additional monitoring. There are three needs in relation to this priority: there is a need to monitor new sites, a need to expand surveys of existing sites and a need to re-commence surveys at sites that are no longer counted. Target sites are listed below: • Establishment of new waterbird monitoring sites, either as part of the BOCA Western Port Survey or as a separate but parallel program. These sites should be: - Watson Inlet and two roost sites near the southern side of the Yaringa Marina entrance - Middle Spit mud banks and Crawfish Rock

- The mud banks to the either side of the North Arm channel (north section), mud banks around Charing Cross Island (Tooradin channel), and Joes Island in the centre of the North Arm channel.

• Expansion of current monitoring efforts through increased survey area. This would ideally occur at: - Barrallier Island – regular visitation of Chicory Lane reef - Mick’s Beach - Spit Point.

• Re-incorporation of sites that are no longer counted to maintain survey consistency and to allow for the possibility that these sites vary in a decadal time frame in their importance and may become important again in the future. These are: - The Duck Splash - Settlement Road foreshore

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- Blue Gum Point.

At the very least, it would be helpful to include these additional sites on an occasional basis, even if it is not practical to cover them all on every survey date.

4.6.2.2

Seagrass and its associated biota

Changes in seagrass appear to influence population dynamics of a number of waterbird species, either through their affects on fish production, or potentially through changes to benthic productivity. However, the magnitude of this effect is not known and the pathways of influence are unclear. Clearly, prudent management of fisheries is important, as is protection of important fish nursery habitat like seagrass. Therefore, it is important that annual (and seasonal if possible) baywide monitoring of seagrass is continued and expanded to incorporate more parts of the bay at a finer scale. The investment in and development of remote-sensing and GIS-based approaches might be a suitable alternative for on-ground monitoring. Alternatively, the establishment of more monitoring plots, randomly placed within a selection of key areas that correspond to important waterbird and fish habitat, would also provide important information on seagrass availability.

4.6.2.3

Hydrodynamic modelling

There is a clear and increasingly urgent need to understand how intertidal areas vary in their availability for shorebirds and other intertidal foraging species. Hydrodynamic modelling of intertidal mudflat availability is a complex but important area of research that is relevant to this question. In order to undertake this type of work, monitoring stations need to be established to collect data on mudflat exposure over time with different tide cycles and weather conditions. This information will allow a better understanding of real-time foraging habitat availability, and could be used define critical limits for intertidal reclamation.

4.6.3

Communication and messaging

In a parallel study that investigated community understanding and attitudes to Western Port and its waterbird values, Christie et al. (2010) found that local people and Western Port users generally had a good level of understanding about the natural values of Western Port and were amenable to a range of possible behavioural changes aimed at improving waterbird conservation in the region.

Opinions on the most effective means of communicating management recommendations to users of Western Port were canvassed and the results indicated that signs placed at key sites are likely to be the most cost-effective method for engaging and informing the community. There are currently several roost sites that are subject to disturbance from recreational activities, which would benefit from the placement of new signs or the updating of existing signs. These are: • Barrallier Island • Stockyard Point • Tortoise Head • Reef Island • Observation Point.

Signs placed near high-tide roosts should be clear, bold and contain information about bird behaviour that is relevant to the problem of disturbance.

There is also a need to update or install signs at all the major boat ramps around the bay. These signs should be a standard format with minimal writing and conceptual images/figures. Boat ramps to target are: • • • •

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• • • • •

Stony Point Blind Bight Cannons Creek Corinella Yaringa (possibly, depending on budget).

Boat ramp signs should be generic and contain information that is more interpretive.

One of the persistent issues with signs is they will attract people to approach where they otherwise might not have. The other issue is that people often ignore signs, probably due to their prevalence, and installing more signs may be ineffective. Monitoring of people’s use of or attention to signs would be very informative in determining their long-term usefulness. Alternative communication strategies that may be effective in engaging the public are print media, brochures, notice boards, school visits, field days and the production of a Western Port Education Kit (Christie et al. 2010).

The production of a primary school education kit by BOCA (available at: http://www.boca.org.au/learn-about-birds/education/shorebirds-kit) was an important step in this direction.

4.7 Concluding remarks An important output of this study is the provision of information (mapping, report, technical advice, etc.) to follow-on projects including the Port Phillip and Westernport Catchment Management Authority Ramsar Protection project and Port of Hastings environmental impact studies for proposed developments. Such collaboration should be encouraged to ensure that new projects link with existing or completed projects that share similar themes. This will help avoid duplication, improve information sharing among stakeholders and management agencies, and help target and build upon research, management and policy requirements.

The likely impacts of climate change on water-dependent species like waterbirds in Western Port and elsewhere are still a matter of discussion requiring further analyses. It is clear, however, that the reliance of many species on intertidal and near high-tide habitat puts them immediately at a higher risk than their terrestrial counterparts. Simplistically, intertidal foraging areas would be predicted to be the first habitat affected by sea level rise. This will depend on changes in coastal processes associated with climate changes including sediment dynamics. More important will be the potential impact on high-tide roost sites. Many of these occur in geomorphologically inflexible locations (e.g. islands) and others occur in areas that have undergone significant coastal modification (e.g. levee banks). Furthermore, most are subject to the pressures of a growing human population, namely increasing disturbance at high tide and increasing predation pressure from cats and foxes.

The future availability and protection of high-tide habitat will be critical to mitigate the cumulative impacts of increasing individual threats. The best way to collectively manage these threats is through strategic land acquisition. This will enable not only the provision of hinterland habitat in the event of sea level rises, but will also improve opportunities to create adequate buffers around key sites. While other mitigation measures such as the creation of artificial roosts may serve in the interim, they should not be used as surrogates for protecting and maintaining habitat into the future.

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Appendix 1. Details of species trends from 1973â&#x20AC;&#x201C;present at each count site in Western Port Site abbreviations are provided below tables. Site trends as follows: D=declining (red highlighting); I=increasing (green highlighting); V=variable; S=stable; ?=insufficient data to clarify trend; - =insufficient data or no records. LWB = Large wading bird; Palae waders = Holarctic shorebirds.

Species

SPHI

HAST WARN BI/NWFI TOOR

BRYC SETRD

QUE

PIONALL BASRF OBS TORT RAMS BLUE DWY NEW CHUR FAIR LONG Guild

Data range

BAR-TAILED GODWIT

-

-

-

V

-

V

-

-

I

-

I

V

D

-

-

-

-

V

-

Palae waders

1973-2010

BLACK-TAILED GODWIT COMMON GREENSHANK

V

-

-

D

-

D

-

-

I

D

V

?

-

-

-

-

-

I?

-

Palae waders Palae waders

1973-1987 1973-2010

COMMON SANDPIPER CURLEW SANDPIPER

D

-

-

D

-

D

D

-

D

D

D

D

D

D?

-

-

-

D

D?

Palae waders Palae waders

1973-1194 1973-2010

EASTERN CURLEW

V

-

-

D

-

D

-

V?

V

D

D

D

D

V

-

-

-

V

V

Palae waders

1973-2010

GREAT KNOT GREATER SAND PLOVER

-

-

-

-

-

-

-

-

-

-

-

D?

?

-

-

-

-

-

-

Palae waders Palae waders

1973-1987 1973-2010

GREY PLOVER

-

-

-

?

-

?

-

-

-

-

-

?

-

-

-

-

-

-

-

Palae waders

1973-1993

GREY-TAILED TATTLER LESSER SAND PLOVER

-

-

-

D -

-

-

-

-

-

D -

-

D

D V

-

-

-

-

-

-

Palae waders Palae waders

1973-2010 1973-2010

PACIFIC GOLDEN PLOVER RED KNOT

-

-

-

D V

-

D? -

-

-

V

-

V

D -

D -

-

-

-

-

-

-

Palae waders Palae waders

1973-2010 1973-2010

RED-NECKED STINT

D

-

-

I

-

V

D?

-

I

V

V

V

D

D

-

-

-

I

D

Palae waders

1973-2010

RUDDY TURNSTONE SHARP-TAILED SANDPIPER

? ?

-

-

V D

-

V

-

-

I

D V

-

V V

V ?

-

-

-

-

V V

-

Palae waders Palae waders

1973-2010 1973-2010

TEREK SANDPIPER

-

-

-

V

-

D

-

-

V

-

-

-

-

-

-

-

-

-

-

Palae waders

1973-2010

WHIMBREL BLACK-FRONTED DOTTEREL

-

-

-

?

-

V -

-

-

D -

-

I -

V -

-

-

-

-

-

-

-

Palae waders Aust Waders

1973-2010 1973-1987

BLACK-WINGED STILT DOUBLE-BANDED PLOVER

-

-

-

?

-

S

-

-

V

D?

V

S

D

-

-

-

-

I?

-

Aust Waders Aust Waders

1973-1987 1973-2010

HOODED PLOVER

D?

-

-

-

-

-

-

-

-

-

D

-

-

-

-

-

-

-

-

Aust Waders

1973-1994

MASKED LAPWING PIED OYSTERCATCHER

I? I

D -

D -

D I

V -

D D

?

-

D -

D I

V D?

I V

D I?

D D

D? I?

-

-

-

V I

D I

Aust Waders Aust Waders

1973-2010 1973-2010

RED-CAPPED PLOVER

D?

-

-

-

-

I

-

-

S

S

-

D?

S

-

-

-

-

V

D

Aust Waders

1973-2010

-

-

-

-

-

-

-

-

D -

-

?

D?

?

-

-

-

-

-

?

Aust Waders Aust Waders

1973-2010 1973-2010

RED-NECKED AVOCET SOOTY OYSTERCATCHER

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Species

SPHI

HAST WARN BI/NWFI TOOR

BRYC SETRD

QUE

PIONALL BASRF OBS TORT RAMS BLUE DWY NEW CHUR FAIR LONG Guild

Data range

AUSTRALASIAN GREBE

D?

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Grebes

1973-2010

GREAT CRESTED GREBE HOARY-HEADED GREBE

D

-

-

V

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Grebes Grebes

1973-1987 1973-2010

AUSTRALASIAN SHOVELER AUSTRALIAN SHELDUCK

?

-

-

V

-

I

D?

?

V

D

-

V

?

?

-

-

-

V

-

Ducks Ducks

1973-1987 1973-2010

AUSTRALIAN WOOD DUCK

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Ducks

1973-1987

V D?

-

-

V ?

-

V V

-

-

V D

I ?

I -

V -

?

-

V? -

-

-

-

I? -

-

Ducks Ducks

1973-2010 1973-2010

HARDHEAD

D

-

-

?

-

V

-

-

D

?

-

-

-

-

-

-

-

-

-

Ducks

1973-1987

MUSK DUCK PACIFIC BLACK DUCK

D? V

-

-

D

-

V D

D? -

?

-

V ?

?

-

-

-

-

-

-

-

-

-

-

Ducks Ducks

1973-2010 1973-2010

PINK-EARED DUCK AUSTRALIAN PELICAN

V

I

V

D

D

D

-

-

V

?

V

D

D

-

-

-

-

D?

V

Ducks Fishers

1973-1987 1973-2010

CHESTNUT TEAL GREY TEAL

BLACK-FACED CORMORANT

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Fishers

1973-1987

CASPIAN TERN CRESTED TERN

D

-

-

V D

-

S D

-

-

V D

D? V

I V

D? V

D? D

S?

-

V?

-

S? V

D? V

Fishers Fishers

1973-2010 1973-2010

FAIRY TERN

-

-

-

V

-

-

-

-

-

V

-

V

D?

-

-

-

-

-

-

Fishers

1973-2010

GREAT CORMORANT GULL-BILLED TERN

D -

-

-

?

-

-

D -

-

-

D? -

D -

D -

D? -

D? -

-

-

-

-

-

-

Fishers Fishers

1973-2010 1973-2010

LITTLE BLACK CORMORANT LITTLE PIED CORMORANT

V V

?

?

D

D? D

V D?

D D?

D?

-

?

V V

?

I

?

D

V

-

-

-

-

V D

-

Fishers Fishers

LITTLE TERN

-

-

-

D?

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Fishers

1973-2010 1973-2010 1973-1987 1991-2010

PIED CORMORANT

I?

-

I?

D?

-

D

-

-

V

I

I?

D

D

?

-

-

-

D?

-

Fishers

Arthur Rylah Institute for Environmental Research Technical Report Series No. 222

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1973-2010

Western Port Welcomes Waterbirds: Waterbird usage of Western Port

Species

SPHI

HAST WARN BI/NWFI TOOR

BRYC SETRD

QUE

PIONALL BASRF OBS TORT RAMS BLUE DWY NEW CHUR FAIR LONG Guild

Data range

AUSTRALIAN WHITE IBIS

V

D

V

V

V

D

D

D

V

V

D

D

D

V?

-

D?

D

D

D

LWB

1973-2010

GREAT EGRET INTERMEDIATE EGRET

V -

-

V -

I -

I -

D -

-

-

V -

-

I -

?

-

-

-

-

-

-

-

-

LWB LWB

1973-2010 1973-1987

LITTLE EGRET NANKEEN NIGHT HERON

-

-

?

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

LWB LWB

1973-1987 1973-2010

ROYAL SPOONBILL

D

?

-

V

?

D

-

-

V

V

?

V?

?

-

-

-

?

V

V?

LWB

1973-2010

STRAW-NECKED IBIS WHITE-FACED HERON

?

V

D?

D

?

D

D?

V D

D? D

D

I D

V D

D? V?

?

D

?

D

?

D

-

-

-

D

V?

LWB LWB

1973-2010 1973-2010

WHITE-NECKED HERON

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

LWB

1973-1987

YELLOW-BILLED SPOONBILL EURASIAN COOT

D

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

LWB Rail

1973-1987 1973-1998

PURPLE SWAMPHEN BLACK SWAN

I

?

I?

I V

-

D

?

D?

D

S?

V

D

V

D

-

-

?

V

V

Rail Swan

1973-2010 1973-2010

PACIFIC GULL

S

D

I

V

I

D

D

D

D

I

V

D

V

D

-

D

-

D

D?

Gulls

1973-2010

SILVER GULL WHISKERED TERN

D -

D -

V -

D -

D? -

D -

D? -

D? -

I -

V -

D -

D -

V -

D? -

-

?

-

-

V -

?

-

Gulls Marsh tern

1973-2010 1973-1987

SPHI = Sandy Point/Hann’s Inlet/HMAS Cerberus settling ponds HAST = Hastings WARN = Warneet BI/NWFI = Barrallier Island/north-west French Island TOOR = Tooradin BRYC = Bunyip River/Yallock Creek SETRD = Settlement Rd foreshore QUE = Queensferry PIONALL = Stockyard Point/GMH drain & Pioneer Bay/Blackney’s Rd BASRF = Reef Island/Bass Bay

66

Arthur Rylah Institute for Environmental Research Technical Report Series No. 222

OBS = Observation Point TORT = Tortoise Head RAMS = Rams Island BLUE = Blue Gum Point DWY = Dwyers swamp NEW = Newhaven CHUR = Churchill Island FAIR = Fairhaven LONG = Long Island

Western Port Welcomes Waterbirds: Waterbird usage of Western Port

Appendix 2. New mapping of individual high-tide roost sites in Western Port.

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ISSN 1835-3827 (print) ISSN 1835-3835 (online) ISBN 978-1-74287-182-0 (print) ISBN 978-1-74287-183-7 (online)