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Front Cover: Bittern at Minsmere Peter

Partington


SUFFOLK BIRDS VOL. 57 A review of birds in Suffolk in 2007

Editor Nick Mason

Greatly assisted by Philip Murphy (Systematic List) Brian T h o m p s o n (Data) A d a m Gretton (Papers) Trevor Kerridge (Photos) Tony Howe (Artwork)

Published

by

S U F F O L K N A T U R A L I S T S ' SOCIETY in collaboration

with

SUFFOLK ORNITHOLOGISTS' GROUP

2008


Published by The Suffolk Naturalists' Society, c/o The M u s e u m , High Street, Ipswich IPI 3QH Š The Suffolk Naturalists' Society 2008 All rights reserved. No part of this publication may be reproduced. stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior permission of the Copyright owners.

The SNS is a Registered Charity No. 206084.

ISSN 0 2 6 4 - 5 7 9 3

Printed by Healeys Printers Ltd, Unit 10-11, The Sterling Complex, Farthing Road, Ipswich, Suffolk IPI 5 A P .

/

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CONTENTS Page Editorial and Review of the Year: Nick Mason T h e Bittern Botaurus stellaris population on the Suffolk coast and the potential vulnerability to sea level rise: Simon Wollon and Chris Lodge Guidelines for the identification of Caspian Gull Larus cachinnans: Brian Small T h e Return of Nesting C r a n e s Grus grus to the Fens of eastern England: Norman Sills Changes in a House Martin colony in north Suffolk during 25 years: Peter J Dare Marked decreases of s o m e migrant passerine breeders in the Walberswick/ Dunwich Forest area in 2007: David Pearson Report of Ringed Plover Survey, 2007: Mick Wright Suffolk Spotted Flycatcher Survey, 2007: Anthony Chapman T h e B a m h a m Goosanders: A New Breeding Bird for Suffolk: John Law T h e 2007 Suffolk Bird Report: Introduction Systematic List Appendices List of Contributors Gazetteer Earliest and Latest Dates of S u m m e r Migrants A Guide to Recording Birds in Suffolk Rare Birds in Suffolk 2007: David Walsh Suffolk Ringing Report 2007: Andrew Gregory Regional Review: Adam Gretton

4 8 . 13 24 . 28 36 39 42 45 47 49 155 159 161 163 164 168 171 180

List of Plates Piale

Facing

No.

Page

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.

Cranes at Lakenheath Andy Hay Crane Habitat RSPB 4th W Caspian Gull Marks Breaks 2nd CY Caspian Gull Peter Wilson 2nd CY Caspian Gull Sean Nixon 3rd CY Caspian Gull Peter Wilson 3rd CY Caspian Gull Peter Wilson 4th CY Caspian Gull Peter Wilson Spotted Flycatchers Bill Bastón Spotted Flycatcher Bill Bastón Black-necked Grebe Bill Bastón Great White Egret Sean Nixon Rough-legged Buzzard Alan Tate Roseate Tern Sean Nixon Lesser Yellowlegs Chris May ne Long-billed Dowitcher Bill Bastón Grey Phalarope Dave Crawshaw Great Skua Sean Nixon Sabine's Gull Sean Nixon

Facing

Plate

Page

No.

20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37.

48 48 48 48 49 49 49 49 49 49 80 80 80 80 81 81 81 120 120

Glaucous Gull Alan Täte Little Auk Sean Nixon Wryneck Bill Baston Woodlark Bill Baston Black Redstart Alan Täte Ring Ouzel Bill Baston Grasshopper Warbier Bill Baston Blackcap Bill Baston Barred Warbier Bill Baston Lesser Whitethroat Justin Zanthoer Firecrest Bill Baston Whinchat Bill Baston Pied Flycatcher Alan Täte Red-breasted Flycatcher Mike Parker Penduline Tit Chris Mayne Serin Bill Baston Yellowhammer Bill Baston Twite Alan Täte

F r o n t c o v e r : Bittern at M i n s m e r e Peter Partington T h e c o p y r i g h t r e m a i n s that o f the p h o t o g r a p h e r s a n d artists

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120 120 121 121 121 121 121 121 160 160 160 160 160 161 161 161 161 161


Suffolk Birci Report

2007

Editorial and Review of the Year In November 2007 the Bird Atlas work began. As everyone should know this involves both Winter and Breeding Surveys covered on a tetrad (2km square) basis. The first bird recorded, as a roving record was a Tawny Owl at just after midnight on November 1st! Throughout November hundreds of thousands of records were added to the BTO website. Whilst these roving records are of importance for showing the distribution of bird species it is the tetrad recording that shows the abundance of birds and where the most valuable fieldwork is being done. In Suffolk the uptake of squares has been excellent with more people becoming involved as they see the survey unfolding. There are 1100 tetrads in Suffolk. So far (at time of writing) 591 have been taken up with over 230 participants. It is hoped that every tetrad will be covered in the four years of the survey. At the end a report will be produced that should be as thorough as any produced before. Interestingly, it is the first time that many birders have entered their data electronically onto the efficient and user-friendly BTO website, saving a good deal of time and effort for coordinators. It has to be added that this is not compulsory and won't be for the foreseeable future. Let's hear it for all the volunteers who are giving up their free time to go out and spend the morning (two hours for a tetrad count), either locally or further afield, counting our birds. By the third and fourth recording years there will be only a few gaps left to fill. Some of these are likely to be in the west around Haverhill where traditionally there are fewer birdwatchers but where, no doubt, isolated or previously unknown pockets of bird populations are waiting to be found. It is worth noting again that our Regional Organiser for Suffolk is Mick Wright who can be contacted on 01473 710032 or by email at mickwright@btinternet.com. Mick, of course, coordinates most of Suffolk's bird surveys. Much of the information used in this Report has been gathered by volunteers, during organised surveys or during casual birding. There are over 2500 WeBS counters in Britain, covering both the estuaries and inland water bodies. In Suffolk there are over 60, some of whom never miss a count. They share the load but they choose to go out in all sorts of weather. Robert Johnson, who helps on the Deben, is one of them and, typical of all the rest, given a problem (such as someone having a broken leg!) he will help to sort it out. Offer him some tetrads to survey and you receive a positive response. There are 61 individuals doing Breeding Bird Surveys (BBS) in Suffolk. Data is received each year from Orfordness and Landguard, much of it through ringing. These birders, like the rest of the county's ringers, are mostly volunteers. The UK is one of the best recorded countries in the world for birds and Suffolk can hold its head high both for coverage and detail. We have a very good, and building, knowledge of our avifauna. We would encourage all birders, especially youngsters, to get involved in some way with Bird Surveys. A BBS does a great deal to help us understand bird populations and helps in conservation. Let's face it there are still a number of bird species that need our help. At the same time, surveying birds can help to improve one's identification skills, especially bird sounds. Committees are not everybody's cup of tea! If we are to coordinate the birding data and create a report such as this, however, they are needed. There were three Bird Recorders in the county in 2007. Andrew Green, Colin Jakes and Eddie Marsh are all volunteers who collate the records for their area and pass it on so that the species reports can be written. The Suffolk Ornithological Records Committee has overall responsibility for the recording of the birds in the county. It also has to make decisions on the rarities that are found and that it is

4


Editorial and Review of the Year mostly made up of our peers who have special and impressive skills in identification. The secretary of that committee is Justin Zantboer, another volunteer, who spends hours coordinating the bird records in Suffolk. He has been a great help in bringing together this Report. Recording birds should not just be about the rarer species. There are now 59 races and species of bird in the UK with a Biological Action Plan (BAP). Some of them do not occur in Suffolk and others may winter here or pass through. We started with 14 species and it is worth listing them - Grey Partridge, Bittern. Stone-curlew, Turtle Dove, Nightjar, Woodlark. Skylark. Song Thrush, Spotted Flycatcher, Tree Sparrow, Linnet. Bullfinch, Reed Bunting and Com Bunting. Last year more were added, indicating that there are further species still on a downward trend. Among these. and relevant to Suffolk, are Lapwing, Curlew, Cuckoo, Lesser Spotted Woodpecker, Tree Pipit, Yellow Wagtail, Dunnock (yes Dunnock), Grasshopper Warbier, Willow Tit, Marsh Tit, Starling. House Sparrow. Hawfinch and Yellowhammer. Barn Owl is included as a Local Character BAP species for Suffolk. For some the outlook is far rosier than others. In Suffolk the results of the Ringed Piover survey suggest that it too should be on the list. Ali records received by SORC that relate to these birds are useful. The progress being made can be seen in the Systematic List and in the Bittern and Spotted Flycatcher papers. Honey Buzzard Hopefully the Atlas work will shed more light on the status Peter Beeson of these species. For their help in producing this report I would like to thank ali the section authors of the Systematic List for their splendid input. It takes a lot of effort to bring together ali the data, in their own time. Their names are at the beginning of their section. Progress was slowed down somewhat this year by computer glitches and by the switch to Mapmate as the preferred vehicle for sorting the records you all send in. Hopefully, as the County Recorders become more familiar with what to them is a new programme, things will become more efficient and easier. Some of the records initially come in via the excellent BINS service. This was a welcome development in 2007. Standing for Birders Information Network Services it is basically a pager service for the mobile phone. There is also an interactive website, including a chat room. Congratulations should go to Roy Marsh and Lee Woods for their commitment. Such a service must have its health warning, however, and no report can be considered 100% accurate. A special mention needs to be made of Philip Murphy without whom this Report would not be published. His meticulous checking of reports and the data within them is legendary. No one has a greater depth of historical knowledge of our birds than Philip. The Ringing Report this year has been written by a non-ringer. Andrew Gregory has produced a piece which is typically his style. We always welcome feedback and so let us know what you feel about this departure from the norm. It is certainly easy to read and informative. My thanks must also go to Adam Gretton, Trevor Kerridge and Tony Howe for their continued input and support. Laurie Forsyth has also been of great assistance, to this novice.

5


Suffolk Birci Report

2007

by giving much of the Report a final check-over for typo errors. Su Gough and Peter Beeson regularly provide artwork for the Report. I am sure that you will agree that their input continues to be of a very high standard. Likewise Peter Partington's front cover of a Bittern maintains that high standard. There is a mixture of papers. Norman Sills writes about the Cranes and their breeding attempts at Lakenheath Fen, while Simon Wotton and Chris Lodge give us an RSPB perspective of the state of the Bittern population in Suffolk and future worries concerning salt water inundation on the coast. David Pearson has written about the change in fortunes of Willow Warbler and Sedge Warbler in the Walberswick/Dunwich forest area over recent times. You may need some black coffee to get through Brian Small's excellent piece on the identification of Caspian Gull in one sitting. Personally I have it on paper and will keep it in my car for winter visits to the Blyth! As Brian states, the identification of Caspian Gull is not for the faint-hearted or the novice. Peter Dare has written about the population of House Martins on his house over 25 years. Mick Wright has given a report of the Ringed Plover survey. I am pleased that we also were able to include brief details on the Spotted Flycatcher survey of 2007 and the breeding Goosanders on the Little Ouse. Throughout the report we have tried to be as accurate as possible. The latest BOU checklist has been followed and the full species name has been used initially in the Systematic List. After that I consider it more useful to shorten it - so it's an Oystercatcher not Eurasian Oystercatcher. To the best of our ability the records are correct, if there are errors then please let us know so that corrections can be made next year. Again it is worth asking for records on a regular basis, in good time and, if possible, on the SOG recording sheet which can be downloaded from the website. This sheet is user-friendly requiring the usual details such as site, map reference, date and any interesting comments. The names of the Bird Recorders are on the inside front cover. Eddie Marsh will stand down at the beginning of 2009, but 2008 records need to go to him. I feel moved to remind birders that birding/bird watching is supposed to be fun. This doesn't mean that it cannot be serious. On a similar theme, the acceptance or non-acceptance of a record is for the relevant committee to decide and the verdict must be considered final. Chasing a year list is all well and good but it should never be to the detriment of accurate Suffolk recording. Any comments regarding this Report will be gratefully received! Do we have the right format and are the papers suitable? What would be the response to a change in size? For example the Gwent Report measures 17cm x 24.5cm (ours is 14.7cm x 21.0cm). The larger size allows for a better lay-out and more flexibility with photographs and drawings. If you have the opportunity to peruse a larger Report please do so and give us feedback. I know that most people will have their back copies in a neat row on a bookshelf; would the change cause too much upheaval? Once again I would like to thank all those who have helped to put this Report together. I started out worrying about what I had taken on but it is so much easier when you receive such a positive response from others. I make no apologies for mentioning volunteers again. They are the backbone of what this report is about. Volunteers also are out there doing the conservation work that has lead to some of the positive changes in our bird populations. As a warden myself I am so thankful for the group who come out and help restore the heathland habitat that has seen great success over the past years. And a great thank you to all those farmers and landowners who are attempting to help wild birds. It would be easy to be pessimistic about the state of our bird populations in Suffolk and there are some very disappointing statistics, although many of them are more to do with

6


Editorial and Review of the Year conditions in their wintering quarters than the habitat available for them here. Tree Pipit is one of those species. However. there is a lot to be positive about. Several speeies are "doing well" and the populations of others are expanding. Dartford Warblers and Little Egrets may be here because of climate change but they wouldn't be if the habitat was not right. Brief Review of the year 2007 started well weather-wise and the sunshine and warmth of April continued into the first half of May. After that the summer disappeared with a good deal of rain and dull skies and tempĂŠratures on some days being way below the average. The May Bank Holiday was atrocious with rain all day on the Monday causing many young birds to perish. Early breeders such as Woodlark had brought off a brood by then and the later arrivais may have fared better. The second half of June and most of July was also wet and August wasn't much better. For those of us who look forward to watching and monitoring summer insects it was a dead loss with hardly a continuous blue sky ali summer. Despite ali this many bird species bred successfully as can be seen in the Systematic List. The bird of the year must be the Squacco HĂŠron at Minsmere on July 13th. This beautiful adult bird unfortunately only stayed for one day having devoured several of the dragonflies on the Levels. The cool weather benefited this bird! A report can be found in the UK rarities section. Suffolk's third Red-flanked Bluetail at Corton was, unfortunately, also only seen on one day, September 28th. The Long-billed Dowitcher on the Stour and the Lesser Yellowlegs, which was often seen at Southwold Town Marshes, were both long stayers. Following on from the successful establishment of the Little Egret population. Suffolk's fourth Cattie Egret and at least five Great White Egrets were present in 2007. One or both ofthese two species are being touted as breeders in the near future as the former particularly is doing well in the south-east of the country. Which one is your money on - and will they breed successfully before Spoonbills eventually do? For many the chance to catch up with Penduline Tits may have been the highlight of the year. Although elusive at Minsmere four birds then tumed up at Dingle Marshes, Walberswick and were often quite confiding as they fed near the old windmill. Is this the next species to breed in Suffolk? Perhaps they already have! The possibility of an Iberian Chiffchaff at Lavenham, from Aprii 13th into July got a few puises racing. The current consensus is that it was a hybrid. The way that Peter Hobbs followed up this bird, however, was most impressive as can be read in British Birds 101. Less rare but always a welcome sight were the hundreds of Little Auk in November. The write-up of this species is rather long but does include several interesting observations that we are keen to keep. Nick Mason


Suffolk Birci Report

2007

The Bittern Botaurus stellaris population on the Suffolk coast and the potential vulnerability to sea level rise Simon Wotton & Chris Lodge Species Monitoring & Research, Conservation S c i e n c e , R S P B , T h e L o d g e , Sandy, Bedfordshire S G I 9 2 R E Introduction Up until the early I8th Century, the Bittern was common in the fens of northwest Suffolk, and probably bred at sites along the coast (Payn 1978: Piotrowski 2003). Land drainage and réclamation, as well as persécution, resulted in a steep decline in numbers and breeding probably ceased in Suffolk in the 1860s. The Bittern became extinct as a breeding species in the UK in 1886, but nesting was confirmed again in 1911, at Hickling Broad in the Norfolk Broads. Bitterns bred again in Suffolk in 1929, at Thorpe Fen, but possibly earlier (Payn 1978). Numbers increased nationally to a peak of about 70 booming maies in the 1950s, with the majority in the Norfolk Broads. In Suffolk. 14 nests were reported at seven coastal sites in the early 1950s (Piotrowski 2003). Although there was a crash in the Suffolk population in the early 1960s, due to the cold winters, numbers recovered to a peak of around 20 boomers at five coastal sites by the early 1970s (Piotrowski 2003). At Minsmere, 12-14 booming males were reported in 1971-73, with 13 in 1976, but by 1991, however, only one boomer was found at Minsmere (Smith et al. 2000). The Bittern is on the red list of the UK Birds of Conservation Concern (Gregory et al. 2002) and is a UK Biodiversity Action Plan (BAP) species. both for its historié decline and current rarity. It's rare and threatened status led to it being listed in Annex 1 of the 1979 EU Directive on the Conservation of Wild Birds and Schedule 1 of the Wildlife and Countryside Act 1981. RSPB and Naturai England have been monitoring the numbers of UK booming male bitterns every year since 1990, and the numbers of UK nesting females since 1994, through the Action for Birds in England programme. During this period. the Suffolk coast has been the key area for breeding Bitterns in the UK. The main aims of the annual survey are to report the minimum and maximum numbers of booming male Bitterns in Britain and the minimum and maximum numbers of nesting females in Britain. The monitoring methods are summarised in the 2008 survey report (Wotton et al. 2008). Breeding Bitterns in Suffolk since 1990 Since the annual monitoring of the UK Bittern population began in 1990, the Suffolk coast has been the core area for booming males and for nests. The number of booming male Bitterns found on the Suffolk coast between 1990 and 2008 is shown in Table I. During this period, numbers on the Suffolk coast have ranged from four (in 1997 and 1998) to 24 in 2008. Since 1990, the low point nationally for booming males was in 1997, when only eleven booming male bitterns were found in the UK. The Suffolk coast population did not recover in 1998. but started to in 1999, driven by an increase in the number of boomers at Minsmere (Figure 1). The improvement at Minsmere was linked to the lowering of reedbeds from 1994/95 (Smith et al. 2000).

8


The Bittern population

on the Suffolk

Coast

Table 1. The number of booming male Bitterns and occupied sites in the UK and on the Suffolk coast, between 1990 and 2008. The annual proportions of the national total of boomers and sites on the Suffolk coast are also shown:

Year

UK

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

18 16 18 15 15 19 22 11 13 19 22 30 31 43 55 46 44 51 76

Booming males Sufiolk % Suffolk coast coast 39% 7 44% 7 39% 7 40% 6 40% 6 47% 9 50% 11 4 36% 31% 4 8 50% 10 45% 15 50% 14 45% 42% 18 19 35% 20 43% 45% 20 20 39% 24 32%

UK II 9 10 9 9 10 10 7 9 11 14 18 20 24 31 28 28 33 42

Sites with booming males Suffolk % Suffolk coast coast 27% 3 44% 4 30% 3 33% 3 33% 3 30% 3 3 30% 29% 2 22% 2 27% 3 4 29% 28% 5 25% 5 21% 5 16% 5 18% 5 18% 5 15% 5 14% 6

Figure 1. The number of booming male Bitterns in the U K . o n the Suffolk coast and at the key site of Minsmere, between 1990 and 2008.

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Suffolk Birci Report

2007

There have been booming Bitterns at only two sites in every year since 1990, Minsmere and Walberswick. There have been booming males at Easton Broad in ali but two of the years. Booming was first recorded at North Warren in 2000 and at the newly created Hen Reedbeds in 2001. Booming was confirmed at a new site on the Suffolk coast in 2008. Annual nest monitoring involves watches for feeding flights, so the figures only refer to nests that reach the chick stage (Wotton et al. 2008). The number of confirmed nesting attempts in the UK and on the Suffolk coast between 1994 and 2008 is shown in Table 2. During this period numbers on the Suffolk coast have ranged from three nests in 1996 (50% of the national total) to 20 in 2003. Figure 2 shows that there has been a slight decline in the number of nests on the Suffolk coast since 2003. Numbers have dropped slightly at Minsmere since eleven nests were found there in 2003, with seven recorded in 2008. Flooding in parts of the site at the end of May is likely to have had an adverse effect on nunibers (Wotton et al. 2008). Easton Broad has also been adversely affected by the regular saline inundations in recent years. Four nests were recorded there in 2006. but there was no evidence of any nests in 2008 (Wotton et al. 2008). Table 2. The number of confirmed Bittern nests and sites in the UK and on the Suffolk coast, between 1994 and 2008. The annual proportions of the national total of boomers and sights on the Suffolk coast are also shown:

Year

UK

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

9 9 6 12 13 20 19 22 26 34 31 27 27 27 39

Confirmed nests Suffolk % Suffolk coast coast , 4 44% 4 44% 3 50% 8 67% 9 69% 85% 17 63% 12 17 77% 17 65% 20 59% 15 48% 17 63% 18 67% 14 52% 15 38%

UK 6 5 4 5 5 5 9 8 11 14 16 12 12 12 20

Sites with confirmed nests Suffolk % Suffolk coast coast 2 33% 2 40% 2 50% 2 40% 40% 2 2 40% 44% 4 4 50% 5 45% 5 36% 31% 5 5 42% 5 42% 5 42% 4 20%

There have been confirmed Bittern nests at both Minsmere and Walberswick in every year since 1994. In this period. there have been between two and twelve nests annually at Minsmere. and one to five at Walberswick. Since 1993, there has been confirmed nesting at three other Suffolk coast sites: Easton Broad. Hen Reedbeds and North Warren. Potential effects of Sea Level Rise By 2050, sea levels along the East Anglian coastline are predicted to be 16-7lem higher than now (EECCP 2007), with increased storminess and wave height likely (Stansby et al. 2006). Thus, tidal inundation of coastal low-lying land in this area is expected to become more frequent. Around two-thirds of sites currently occupied by nesting females in the UK are in danger of inundation from the sea. and most of these are around the East Anglian coastline.

10


The Bittern population

ori the Suffolk

Coast

Recently there have been increased levels of inundation in Suffolk, with inundations of Walberswick, Easton Broad and small parts of Minsmere. Figure 2. The number of confirmed Bittern nesting attempts in the UK, on the Suffolk coast and at the key site of Minsmere. between 1994 and 2008.

Mathematical modelling of Bittern population parameters recently has demonstrated the sensitivity of the UK population to changes in chick mortality, much of which is associated with a small number of sites in coastal Suffolk that are in immediate danger from sea level rise (Gilbert et al. in press). Models of the impact on growth of the UK Bittern population of both partial and complete loss of Bittern nesting and feeding habitat on the most vulnerable parts of the Easton Broad, Minsmere and Walberswick predicted a negative effect even over a short, 10 year. period. Discussion Since wetland restoration and creation work began in earnest. the decline in the size of the UK Bittern population has been halted and reversed and numbers have increased from 11 booming males in 1997 to 76 in 2008 (Wotton et al. 2008). The core area is stili the Suffolk Coast, although there are now encouraging increases elsewhere. The numbers of booming males in The Fens has increased sharply to 12 in 2008, up from two in 2006 and six in 2007 (Wotton et al. 2008). In many years only half, or less than half, of sites occupied by booming male Bittems each year support nesting females (Figure 2). For example, in 2007, booming males occupied 42 sites, but only 20 of these held nesting females (Wotton et al. 2008). Furthermore, the majority of nests in most years have been from the small number of sites located on the Suffolk Coast (Figure 2). It is encouraging, however. that there have been nesting Bitterns in the Cambridgeshire Fens in 2007 and 2008 and in the Somerset Levels in 2008 (Wotton et al. 2008). The dynamics of the UK population are such that its growth appears more sensitive to changes in chick survival than to other demographic parameters. It thus seems likely that any environmental changes that significantly reduce chick survival will affect the growth of the whole population.

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Suffolk Birci Report

2007

Direct impacts on Bitterns are likely to be brought about by an inundation during the nesting season, when a sudden rise in water levels is likely to flood out nests. This has proven to be the case in 2007 and 2008, on the Suffolk coast in particular. As freshwater fish are the main component of the Bittern diet, particularly when feeding chicks (Gilbert et al. 2003), they are also likely to be indirectly affected by the loss of freshwater fish. An inundation that kills the majority of the fish present is likely to have a negative effect on the birds, ali year round. Eventually, it is likely that there will come a point when inundations of the freshwater sites on which Bitterns depend, will become so frequent, that the systems will become mainly brackish, with less predictable water levels and little food for breeding birds. It may be assumed that saline inundation negatively affects Bitterns in the UK and that frequent inundation will lead to the eventual loss of Bitterns and their freshwater habitat. The population modelling in Gilbert et al. (in press) suggests that the population recovery of Bitterns in the UK will decline, or halt at a rate depending on the frequency with which productivity and survival is reduced because of tidal inundation. The modelling suggests that the loss of just a proportion of the suitable habitat at Easton Broad, Minsmere and Walberswick will halt growth and send the population into decline. The results from 2008, however, are encouraging, as there were found to be an increase in booming Bitterns and nests at sites safe from saline inundation (Wotton et al. 2008). Acknowledgements The annual Bittern monitoring programme is jointly funded by RSPB and Naturai England, through Action for Birds in England. Thanks go to the site managers, landowners, Wardens, volunteers, county recorders and local birders who have helped in various ways with the annual Bittern monitoring. References East of England Climate Change Partnership. 2007. Review of current position and activity on climate change mitigation and adaptation in the East of England. East of England climate change partnership, Atkins. Cambridge UK Climate impacts programme, www.ukcip.org.uk. Gilbert, G., Tyler, G .A. & Smith, K.W. 2003. Nestling diet and fish preference of Bitterns Botaurus stellaris in Britain. Ardea, 91: 35-44. Gilbert, G . T y l e r , G.A., Dunn, C.J., Ratcliffe, N. & Smith, K.W. 2007. The influence of habitat management on the breeding success of the great bittern Botaurus stellaris in Britain. Ibis, 149,53-66. Gilbert. G., Brown, A.F. & Wotton, S. The UK Great Bittern population: current dynamics andpredicted vulnerability to sea leve! rise. BOU Bird Conservation. Ibis. (In press) Payn, W.H. 1978. The Birds of Suffolk. Ancient House Press, Ipswich. Piotrowski, S. 2003. The Birds of Suffolk. Christopher Helm, London. Smith, K.W., Welch, G., Tyler, G.A., Gilbert, G., Hawkins, I. & Hirons, G. 2000. Management of the RSPB Minsmere Reserve reedbeds and its impact on breeding Bitterns. British Wildlife. 12, 16-21. Stansby, P., Kuang.C., Laurence, D. & Launder. B. 2006. Sandbanksfor coastalprotection: implications of sea level rise. Part I: application to East Ang/io, Tyndall Centre Working paper 86. Wotton, S., Lodge, C „ Lewis, B, Schmitt. S.. Kellet, K„ Gregory, R. & Brown, A. 2008. Bittern Botaurus stellaris monitoring in the UK: Summary of the 2008 season. Unpublished RSPB Report, RSPB, Sandy, UK.

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Suffolk Birci Report

2007

Guidelines for the identification of Caspian Gull Larus cachinnans - a report for Suffolk Birds Brian Small Given that the British Ornithologist's Union Records Committee has recently, and finally, elevated both Caspian Larus cachinnans and Yellow-legged Gull L. michahellis to full species status, it seems timely to publish further détails on the occurrence and appearance of Caspian Gull in Suffolk. I first published an article in Suffolk Birds in 1999, but the criteria proposed there were somewhat tentative and not very comprehensive (though I still stand by most of what was written). Since then, the identification criteria have become clearer and the status of Caspian Gull in Suffolk has changed; it was, therefore, felt that an update was required. I do not intend to repeat what that article said, but rather, briefly review its status and then outline the ID features. Status The first accepted record of Caspian Gull in Suffolk was at Benacre Broad by John Kemp in 1998. Other records (never submitted or accepted by the SORC, but published by Piotrowski, 2003, e.g. a first-winter at Wetherden in 1997) pre-date this, but following the first scattered sériés of records, I believe that with careful observations at key sites, a pattern has begun to emerge. A small number appear in early autumn, often these are young birds (juveniles/first-winters), possibly overshooting from Poland or the Netherlands. Older (returning?) birds appear a little later in the autumn or early winter (up to late December, early January), possibly getting pushed out of the continent or simply moving more leisurely to the wintering areas - I would further speculate that many of these birds are actually moving inland to winter at other sites. Mid-winter records are possibly rarer than at other times, though one or two obviously hang around at some sites (pig fields or refuse tips, and associated roosting/bathing sites), but increasingly they are tending to over-winter further inland. There is another obvious peak of records in late February and March, possibly associated with birds exiting the UK via the Suffolk coast. Records throughout the rest of the year are sporadic, and are likely to be immature birds that have no desire to migrate. (Photographs can be found in the first set of plates to go alongside this article - Ed.) Identification It is obvious that though Caspian Gull is stili a difficult gull to identify, an increasing number of observers have gained the important key experience of cachinnans - experience is nearly always the key with large white-headed gulls. An in-depth knowledge of ail taxa, especially in comparison with michahellis, is very important and should be looked for in detail during observation and then subsequently in any description. In my opinion, identification of cachinnans is going to be easier for those with a lot of experience, and if they have it they need to express it, and it is also important to take this into account when assessing records, particularly when such subjective terms as 'snouty', 'high-chested' and 'elongated', etc. are used in the process. I cannot stress too much that experience is the most important element in identifying Caspian Gull. As will be seen in what follows, so much of what I describe is relatively subjective, and draws heavily upon knowledge of the variability in the common large whiteheaded gull species, especially Yellow-legged Gull. Also, some things (like structure and mantle tone) are very subtle, as is the effect that wear can have on feathers and consequently the pattern and mixture of âges of feathers on the bird. A good example of this would be a

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comparison of second-winter Caspian and Yellow-legged Gulls in late winter, where the mix of feathers is slightly more advanced on Caspian, and the younger-looking feathers much more boldly pattemed on Yellow-legged (and this leaves aside ali of the other subtle things like variability in structure and bare part shape and colour). At the risk of sounding a 'gullsnob', the identification of Caspian Gull is not for the uninitiated or faint-hearted. Structure Caspian Gull has a structure that gives it a distinctive look, going across ail âges, but one that can be matched in almost ail respects by some michahellis. It appears quite long-legged and it often seems to stand taller than argenteus (but less so than argentatus), whilst next to michahellis it often looks less chunky and longer - there is a lot of body behind the legs though many michahellis, especially eastern, can also possess such a look. The head seems quite small for the body, and I feel the often-quoted (and over emphasised) snouty look (akin to Great Black-headed Gull L. ichthyaetus) is a resuit of the longer slim bill on a smaller, slimmer head - though, certainly some michahellis can be apparently just as snouty. The head of adults have a slightly steeper forehead than younger birds, producing a more rounded head akin to Common Gull L. canus, and in contrast to the steeper forehead and flatter crown ('square-headed' look) of other large gulls. There may also be a hint of a raised nape, forming a 'step' on the nape. The bill is often (though not always) distinctly longer than michahellis and argentatus/ argenteus, appearing slightly more narrowly based, but more obvious is a more 'tapered' look as the bill gets slimmer towards the tip with a less steep curve to the upper mandible, and less obvious gonydeal angle, so characteristic of argentatus/argenteus and most michahellis. I would not say that the nostril shape or position is something that hits you. though it has been (over-) emphasised in one or two descriptions. The darker eye seems well forward on the head with a large area of the head behind it, though, like the many who state that the eye is smaller, this may be an optical illusion caused by the lack of extensive dark marks around the eye, present in autumn and winter in argentatus and some michahellis (some cachinnans have slight streaking around the eye). Compared with most michahellis and argentatus/argenteus, cachinnans has a higher chest, a 'bosomed' effect - as if holding its breath. The body can be large, but in bulk may only match that of Herring. and the rounded belly gives a boat-like effect. One of the most noticeable structural features is the attenuated rear end; a consÊquence of a low or absent tertial step and relatively long wings. On hot summer days on pig fields they look really lanky - incredibly slim and long-legged. The tail tip is one-third to half the distance from the longest tertial to the wing tip (obvious only in birds that have completed their moult). Most michahellis and especially argentatus/argenteus are less attenuated and have a more prominent tertial step - though the exception proves the rule, and some michahellis (possibly eastern birds) match cachinnans closely. In flight the long- and broad-winged appearance is even greater than for michahellis and is distinct from argentatus/argenteus and the length of the head and neck extension in front of the wings is noteworthy. On a standing or swimming bird the primaries cross markedly more than on Herring Gull. The legs are longer, particularly above the 'knee', in comparison with Herring this is further enhanced by their slimness, and adds to the height of the bird. The feet can look large and in flight they can extend almost to the tail tip. Tone of Mantle On second calendar-year gulls and older a lot of importance has been placed upon the tone of upperparts. In reality, this is of limited importance due to the complete overlap with Herring Gull of the race argentatus, because the tone of the mantle/scapulars is very difficult

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Guidelines

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Gull

to assess on lone individuáis and because varying lighting conditions also produce different contrasts. I summarise my experience below:• michcihellis is on average darker than cachinnans (contra Barth). • cachinnans is well within the tonal range of argentatus/argenteus, and those that I have seen appear somewhere between British Herring and Yellow-legged. • The darkest argentatus are darker than cachinnans, which in turn is said sometimes to appear palé enough to match argenteus, though I have yet to see this personally but is more likely in younger birds. • As well as tone, there is a subtle difference in colour (most obvious in direct comparison), with cachinnans having a more neutral silky grey, less blue than argentatus/argenteus; michcihellis is often particularly slaty or purple-grey. • The argenteus I see in Suffolk vary only slightly and can be used as a good basis for comparison, but, of course, in winter when most cachinnans are present, a good percentage of Herring are argentatus. • cachinnans is invariably an exact match for Common Gull L. C. canus, and canus, when alongside, can be used as a good tonal 'marker'. Moult The moult of adult primaries for all three species starts, on average, within one month of each other. Michahellis is the first to start and complete; cachinnans is slightly later and overlaps with argenteus, with argentatus being the latest to complete - some into December. As an example, the state of the primary moult of an adult cachinnans at Blythburgh in autumn 1999 was either identical to or behind that of the argenteus present. Most adulttype michahellis had shed the outermost primary by early September. The moult of first generation primaries is earlier than adults. Second calendar-year cachinnans drop plO in late July/early August, which is in line with michahellis and argentatus/ argenteus; some second calendar-year michahellis can, like some second calendaryear graellsii, complete primary moult very early, sometimes completing by late July. I summarise my observations below:• Michahellis tends to breed earlier (any lone juvenile in early or mid July is worth looking at closely). They begin to acquire first-winter feathers a lot earlier than argentatus/ argenteus - sometimes in August, one or two months before argentatus/argenteus. Moult into first-winter may be complete by late August; many have new scapulars plus some greater coverts and tertials. (Some argentatus can be seen with extensive first-winter scapulars and, rarely, coverts - by early September). • The post-juvenile head and body moult in late summer/early autumn makes most michahellis appear subtly different to argenteus/argentatus, with a whiter head contrasting with a darker. brown (often worn) juvenile plumage; cachinnans remains relatively white-headed and -bodied. a result of wear/fading or moult, and quite similar to michahellis. • First- (or second-) winter gulls on which the head and body are virtually white in November or December are worth looking at closely, but may not always be cachinnans. Herring Gulls of the race argenteus are looking white-headed increasingly early in Suffolk, even by early January. • During the second calendar year most cachinnans moult the coverts twice: once into a 'first-summer' plumage; then as the mantle moults into an adult-like grey, a number of median, lesser and marginal coverts also moult to an adult-like grey, by November this can be extensive. This results in an advanced plumage unlike most second calendar-year

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michahellis, which frequently appears to have more extensive younger type scapulars and coverts. Both can show grey tertials, but this is more common in cachinnans. Wing-tip pattern of adults The pattern of black and white of the outer primaries on adult Caspian Gull is relatively well documented (ref. Jonsson, 1998 and Garner and Quin, 1997). The pattern of the outer primaries is quite similar (or identical) to argentatus with the extent of black being restricted and white more extensive. The longest, outermost (p 10) has, typically, black along the outer edge of the feather crossing it as a narrow band near the large white tip, and a long white or very pale grey tongue runs along the inner web. Sometimes the white tip meets the tongue and sometimes it has small black notches near the tip. The black on p5 is too variable for it to have any significance when identifying cachinnans. On michahellis the tongue on plO is grey. though a bird observed at Southwold and identified as michahellis had a white tongue (though this might be indicative of a hybrid origin). A good feature to look for is on flying birds, where on the underside the black forms a narrow comma across the outer primaries. The exact pattern of the outer primaries at all ages is worth paying close attention to. A second-winter gull with a white mirror is unlikely to be anything eise (as long as it has been correctly aged). The extent and prominence of silvery white inner edges on first, second and third generation primaries should also be carefully noted. Behavioural characters and voice The 'long-caH' display posture is described as being like that of an albatross, with the head thrown back and the wings out-stretched. On rubbish tips and on the pig fields, cachinnans is aggressive, often adopting this posture towards other gulls - they do seem to like lifting their wings more regularly than other gulls. The call, if heard, is a deep braying, like a Jackass Penguin. Summary of important features Without repeating the previous section dealing with structure, the following summarises for all ages the key features to look for when identifying cachinnans. For each age, pitfalls are drawn to the attention; however, by far the biggest pitfall is likely to be birds with apparently intermediate features, which could well be hybrids. Of those reported in Holland and the UK, some have been putative cachinnans hearing colour rings from breeding colonies of mixed species, for example from Poland, but which do not show 'classic' plumage features. These may well be birds outside the range of those showing identifiable characters, they may be hybrids, but even for those that are ringed as definite cachinnans as a pullus it is important to note that gulls are fairly promiscuous. Both sexes of a pair may mate with birds other than their own mates, and so though the adults are apparently both the same form it does not mean that the young are 'pure' - indeed female/female pairs are not infrequent. •Iuvenile Structure is indicative, but must be supported by detailed examination of plumage. Plumage Fully juvenile plumage lasts until early August, when a patchy moult of scapulars and some coverts takes place (up to 60% of birds are said to moult some upper-wing coverts). There are subtle but cleardistinguishing features, and there are at least four records of birds in this plumage in Suffolk. including a very well-watched bird at the mouth of the River Blyth in 2001.

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Guidelines

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• Head. Compared directly with juvenile argentatus and michahellis, the head is notable for being much whiter than the former and often the latter, though very young birds can have browner marking. Virtually unmarked white from a distance, sparse and fine brownish grey streaks are visible on the rear crown and ear coverts (tightly around the eye, highlighting narrow eye crescents) - if a mask exists it is weak and never as strong as on michahellis. These marks strengthen onto the nape and hind neck, which has an almost uniform sepia wash extending onto the upper mantle. The lores and area around the bill are unmarked. • Seapulars. From a distance these are faded sepia grey (the colour of wet mud), closer up they appear all neatly fringed with a thin cream-white edge, sometimes with faint notehing - they are quite similar in colour to those of juvenile Common Gull. There may be newly moulted seapulars by mid August, which show as black diamonds at their base connected to a thin sub-terminal band in a whitish grey tip, by a dark shaft of variable width (broadest on the fore-scapulars and thin on the rearmost ones). The new seapulars have a greyish tone, which contrasts with the worn sepia juvenile seapulars. • Wing coverts. It is hard to categorise the pattern of the wing coverts. though detailed examination of the patterns of the inner greater and median coverts is very important. Often they are similarly coloured to the mantle, with sepia-grey centres and neat offwhite fringes - dark marginal coverts produce a blackish forewing. The median and greater coverts may appear more broadly tipped whitish and the inner greater (and some median) coverts show characteristic internal pale markings, different from the strongly notehed inner greater coverts of argentatus or michahellis. Dark bases and whitish tips to the greater and median coverts can produce two wing bars - distinet in flight - and this is frequently quoted as diagnostic, but in reality the exaet feather pattern is more important than the overall effect as some michahellis can show the same wing-barred effect. • Tertiais. Contrastingly dark (black or very dark brown as they fade), with neat white edges (thumbnails) at the tips, but occasionally also with faint internal marks near the tip either side of the shaft. This pattern is not diagnostic of cachinnans, some michahellis can show it, whilst graellsii is similar, but has a narrower and more clearly defined edge when juvenile. • Upper-wings. The pattern of the upper-wing is quite distinet: on the inner wing, a black secondary bar and black forewing sandwich paler brown coverts (often with two prominent wing-bars on the median and greater coverts); on the outer wing the outer three primaries are black, but on the next seven silvery 'slats' appear on the inner webs - a pattern echoed on the primary coverts. A pattern never matched by michahellis, though some go a long way towards it, and certainly not argentatus/argenteus. • Underparts. Appears largely white when alongside argentatus/argenteus, but on the breast sides the flanks there are usually brownish blotches or crescents - these may form a broken pectoral band, but the underparts are still distinctly whiter than argentatus and most graellsii. The under-tail coverts are sparsely marked with neat black diamonds or crescents. • Under-wings. A variable feature, though characteristically paler than the majority of michahellis and all argentatus/argenteus. This can be a very distinetive feature on the few that have the under-wings almost entirely white, save for dark marks on the marginal under-wing coverts. However, most often there is faint barring on the axillaries. marginal coverts and the tips of median and greater under-wing coverts; occasionally. the barring is stronger and more extensive, but even so seems whiter. The underside of the remiges, particularly the primaries, is silvery or white, appearing translucent with the outer three appearing dark grey, with a hint of a silvery inner edge, and the tips of the next three

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primaries being darker. On most the inner four primaries look totally silvery white from below. • Tail and tail coverts. A distinctive feature, and likened to the pattern of Rough-legged Buzzard Hulea lagopus, the rump and uppertail coverts look white, but are usually marked with small black spots or bars. The tail is white basally. but shows a broad black tail band. On the proximal edge there is usually a small amount of narrow barring near the black, and there is, when fresh, also a broad white edge to the outer tail feather enclosing the black. On michahellis, the tail band is narrower on the outer rectrices (contra Garner el al.), with the outer tail feathers showing much more limited black, and often (always) there is a prominent white tail tip. • Bare parts. Structurally different (as described above), but the colour of the legs is different; a paler orange- or yellow-flesh, brighter than the legs of argenlatus/argenteus, which are greyer pink, but similar to those of michahellis. Pitfalls The major pitfall for juvenile cachinnans would have to be juvenile michahellis and graellsii: argenlalus/argenteus are, I would hope. different enough not to cause a problem, with strong notching across most of the upperparts and wing coverts. Those graellsii that moult into a very immature-like second-winter plumage can look surprisingly like juvenile and first-winter cachinnans. Michahellis is however the main identification problem. but should be separable on a variety of features, many discussed above: head and bilí structure, juvenile scapulars. wing coverts and tertials are differently patterned. The inner greater coverts are often marked with strong white notching; the tertials have a variable pattern of weak notching on the edges near the tip and some internal marking. First-winter and -summer During the winter. many features are as in juvenile plumage. First-winter plumage is attained by a partial head and body moult, which takes place in September. giving the head a slightly shaggy look, and by the completion of the scapular moult. It is retained until April and May of the second calendar-year, when, for example, wing coverts and the tail start to moult; primary moult starts in late May/early June and is complete in September, by which time second-winter plumage is attained. Plumage Identification characters that should form the basis of identifying first-winter and firstsummer Caspian are as follows. • Head. Usually clean white, but not always unmarked, nearly always whiter than michahellis and argén la tus/a rgen le us, but not always whiter than graellsii. A neat half collar of dark marks on the hind-neck replaces the wash on the hind-neck and mantle of juvenile plumage, though some may still have this brown wash on the upper mantle reminiscent of first-winter Great Black-headed Gull L. ichthyaetus. • Underparts. Like the head. virtually unmarked white, although some faint dark spotting or barring visible on upper fianks, and spots, bars or chevrons on under-tail coverts (a remnant from juvenile). • Mantle and scapulars: When fresh this is made up of even palé sepia-grey feathers, with narrow dark shaft steaks and thin brownish subterminal lines - at a distance looking quite even in tone and colour: michahellis have broader shaft-streaks and subterminal anchors and look more checked in pattern. Sometimes. there is a patchwork of new scapulars showing a pattern of a large black basal diamond joined to a very narrow dark

18


Guidelines

• •

for the Identification

of the Caspian

Gull

subterminal crescent near the tip by a thin black shaft streak. My observations would show that scapulars moulted early are whiter (or bleach white quickly) and these contrast with newer, greyer scapulars - usually the lowest row is moulted last and these may give the appearance of a grey band. As they wear into spring and summer they bleach markedly and can appear virtually white, and at this time a distinct feature may be rows of black spots or diamonds on the bases of the scapulars, particularly on the fore-scapulars. The emphasis in the literature on a less strongly patterned, almost uniform grey is correct for many, but is probably over-stated. Wing coverts. The dark base and pale tips, as described for juvenile (above) form dark and light bands across the wing, contrasting with increasingly worn. even pale biscuitcoloured, median and lesser coverts. From January onwards there may be a few new greyish coverts, and by spring the juvenile coverts look extremely worn: second generation coverts are frequently very similar in pattern to the well-marked pattern of michahellis, the greater coverts in particular may form a dark grey bar across the closed wing. Tertials. These become browner through fading, though the pattern of pale tips is stili visible. Tail and tail coverts. The prominent, even width, black tail band is highlighted by the white base and by new white, unmarked upper- and under-tail coverts. although the latter are still sometimes marked with small crescents. By June the tail feathers begin to moult into a second-generation pattern, with a fairly broad (narrower than michahellis and argentatus/argenteus), but broken. tail band with the black having marbled edges. Upper- and under-wing. The pattern is as in juvenile, though the under-wing often appears whiter with only faint brown barring on axillaries and on marginal under-wing coverts. Bill. Long and slim, tapering towards tip. Düring the winter it is ali dark, sometimes with a lighter greenish or pink-grey base. Düring the spring into the summer the base becomes paler and pinker and a cream tip develops, leaving an indistinct broad band near the gonys.

Pitfalls At this age would be as for juveniles: first-winter michahellis, with white heads and bodies; first-winter and immature-looking. retarded second-winter graellsii, which also have white heads and the slimmer bill and structure associated with cachinnans; surprisingly, first-winter and second-winter marinus can cause confusion at a distance, with white heads and at times a snouty look. Some second-winter L. fuscus (Lesser Black-backed Gulls) complex show more immature-like plumages, with a white head and body, and have sometimes caused confusion. Second-winter and second-summer Late second calendar-year plumage is attained over a sustained period. The increasingly adult-like grey mantle begins to develop in late summer. whilst some wing coverts moult for the second time in six months - in November the median coverts may be missing completely. Primary moult is complete by late September, by which time ali of the plumage has been changed at least once. By spring and early summer of the third calendar-year. the areas of second-generation wing coverts are looking decidedly worn and bleached - in March the greater coverts can seem almost white: the plumage is looking increasingly adultlike. though the bill colour can vary from being pinkish yellow with a dark band near the tip to yellowish with a black gonydeal spot and sometimes a hint of red. An observer should be immediately struck by the structure, and the head pattern and shape.

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Plumage T h e c o m p l e x nature of the p l u m a g e with a p a t c h w o r k of ages of feathers can m a k e cachinnans s e e m m o r e a d v a n c e d at this a g e . though michahellis is f r e q u e n t l y similarly patterned: argentatus/argenteus have a similar plumage pattern by their third calendar-year, but with different-looking primaries, etc. Any Submission should take careful note of many or all of the f o l l o w i n g : • H e a d and underparts. T h e s e are often pristine, u n m a r k e d , and white. In early winter there is a h a l f - c o l l a r of dark spots on the rear n e c k , but this b e c o m e s increasingly unmarked by spring and s u m m e r . • M a n t l e . An increasingly u n m a r k e d mid-grey ( s o m e t i m e s with one or two bleached scapulars), d a r k e r than argenteus and equal to a third-summer michahellis. • U p p e r - w i n g . T h e coverts are a mixture of new grey (usually median and some inner greater), b r o w n i s h blotches on the marginal coverts, hidden on the closed wing, and dark g r e y i s h - b r o w n outer greater c o v e r t s , as in michahellis. By s u m m e r , these s e c o n d generation greater coverts b e c o m e very faded - those on the f o r e w i n g less so, creating a darker leading edge to the w i n g . T h e inner primaries are adult-like g r e y , with slightly paler inner w e b s to the outer primaries forming a 'slatted' pattern that breaks up the black; the secondaries form a broken black band across the w i n g . • Tertiais. Second-generation tertials attained during the s u m m e r of the second calendaryear. have a pattern similar to michahellis: a largely black base, but quite white near the tip with black bars. H o w e v e r , though they are f r e q u e n t l y replaced quite quickly (in N o v e m b e r of the second calendar-year the two shortest are o f t e n adult-like grey and by late winter, they often all look grey), some birds can still retain all-black tertials in March of the third calendar-year. • Under-wing. White. Distinctively the underside of the primaries is also very white with m u c h more restricted black than michahellis and argentatus/argenteus. restricted to the wing tips. T h e majority show a white mirrar of variable size on plO: on s o m e it is no more than a swelling of a pale shaft streak; on others it is very obvious and as large as in the third-generation plO. I have never noted this on second-winter michahellis, indeed it can be absent on third-winter; michahellis appears to have the outer t w o solidly black. • Tail. W h i t e , marked by a broken tail b a n d , though s o m e are m o r e solid and similar to michahellis. • Bare parts. T h e bill is remarkably long and quite Strang and most often is noted as pale creamy yellow (sometimes pinkish yellow in early winter) with a broad black band near the tip. This pattern is kept into the third calendar year as late as July, but some have a m o r e developed bill colour - a colour-banded s e c o n d - s u m m e r bird from G e r m a n y in July 2001 had a yellowish bill with a black spot on the lower mandible at the g o n y s and a hint of red. T h e legs are long, slim and pale pinky or yellow-flesh, more orange-coloured than Herring and perhaps a little less yellow than most michahellis. Iris, dark. Pitfalls I find birds of this age and y o u n g e r really beautiful and possibly, once you k n o w (I mean really know) the features, to be easier than birds aged third-winter and older. They have a unique combination of characters. which make them unmistakable, though oddly some firstwinter cachinnans in March or April can look so advanced (with an almost complete grey mantle and grey coverts) as to be c o n f u s e d with second-winter birds. As the plumage gets m o r e adult-like you rely m o r e heavily on structural differences. particularly f r o m (the main pitfall) michahellis, to identify t h e m , c o u p l e d with detailed e x a m i n a t i o n of the o u t e r

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Guidelines

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primaries. Personally. I cannot foresee confusion with other species, though some older argentatus/argenteus are regularly confused with second-winter cachinnans. Third-winter and -summer By the end of the summer of its second calendar-year, cachinnans is beginning to look much more adult-like - some more than others. It will have undergone a complete moult and attained its third-winter plumage, but close examination of the outer primaries, tail and marginal, lesser and inner greater coverts is needed to confirm this, and to separate it from michahellis. A careful assessment of the following features is essential to rule out michahellis and argentatus/argenteus. Plumage • Head. This seems smaller, finer and. in early winter, whiter than surrounding michahellis and argentatus/argenteus, lacking the bulky feel and usually fairly prominent streaking around the eye. In early winter. a half-collar of sparse dark streaks is visible on the hind neck, but by late winter and into third-summer the head looks completely white, as do the underparts. • Mantle, scapulars and wing coverts. Generally grey, like the adult, but signs of immaturity can sometimes be seen on the marginai coverts, forming spots on the leading edge to the wing. Inner greater coverts may be slightly paler with faint brownish marks. The outer primary coverts show some black and some black might be visible on the bases of the basically grey tertials (Jonsson, 1998). • Tail. This often shows a vestigial tail band of isolated black marks, but may sometimes be white or with minimal marks. • Underwing. The underside of the wing is white apart from restricted black on the outer primaries. The pattern becomes more adult-like, with whitish slivers on the inner edges of the outer primaries, and is very distinct from argentatus and michahellis, which show much more black on the outer primaries. The pattern of plO is variable: some show an advanced adult-like pattern: others have a pattern similar to adult michahellis, with an almost ali dark plO and prominent white mirror, but much larger than third-winter michahellis on which the white is absent or very small; sometimes a small white spot can be seen on p9. • Bare parts. The bill is slim. pale milky or greyish yellow, becoming richer in colour in the late winter. It has a neat dark band near the tip, sometimes with a red 'shadow' on the distai part of the lower mandible. The legs are subtly différent to other forms, pale grey becoming pale flesh-pink on the feet (argenteus may occasionally be grey-pink). The eye always looks dark. The ageing and identification becomes more difficult after the complete moult in the latter half of the fourth calendar-year, by which time cachinnans is intrinsically adult. Some may show dark marks on the primary coverts, and these are the only indications of a fourthwinter plumage. Some descriptions are of 'adults' in August, but the descriptions then describe atypical (more black and less white) patterns for p9 and plO, the chance that these are fourth calendar-year moulting to adult should not be discounted. Adult Come early winter, this age becomes perhaps the most difficult to identify. Up until this time the majority of argentatus/argenteus have streaking on the head (but with subtly différent patterns), whilst cachinnans and michahellis are unmarked (or virtually so). I have found the key features to be structure and plumage détails, in particular head and bill shape.

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Suffolk Birci Report

2007

tone of mantle and a detailed examination of the plO pattern. To re-emphasise a point made earlier, plumage tone will not enable cachinnans to be separated from michahellis or argentatus/argenteus. Fourth-winter birds are basically adults with some immaturity in the bill and primary coverts, but separating them from advanced third-winter birds may be difficult. Though it can be a strikingly large, tali gull, with a long primary projection, not all adult cachinnans stand out from a flock on size alone. The head is small with the crown often looking rounded, a slight raised nape might be noted on some occasions when at rest; when the head is lifted up it is very like a Common Gull. The bill and legs are long, the bill being particularly noteworthy on males. Plumage • Head. Virtually unmarked white at all ages. By early September a few brownish streaks may be visible on the hind neck and above the eye. The remainder of the underparts are white. • Mantle. The mantle tone is very close to that of Common Gull, and I often resort to comparing gulls with canus as a standard tone in varying lighting conditions. In direct comparison with argenteus, it is darker, alongside michahellis and argentatus it is paler. • Tertiais. These have narrow white tips and are held fiat against the body giving a flatbacked appearance. • Primary moult. A little later than michahellis in my experience, matching that of Herring. The exact pattern has been discussed previously, but the timing may give some clues and the opportunity to see the pattern more clearly. In mid-August, an adult may have the outer two primaries showing beyond new and growing primaries just protruding beyond the tertials, and in such a situation the long, whitish inner web can be visible on the upperside of p9 as well as the underside of plO. At various times in September, plO is stili retained, p9 is just beginning to grow; p8 is virtually fully grown, or plO is shed and is beginning to grow, whilst p9 is fairly well grown and p8 is fully grown. The typical pattern of plO for Caspian is described previously. • The pattern of the longest, outermost primary (plO) is typically, black along the outer edge of the feather crossing it as narrow band near the large white tip, and a long white or very pale grey tongue runs along the inner web - some have more black, but on the open wing from above grey inner 'tongues' will always break up the black of the outer primaries. Sometimes the white tip meets the tongue and sometimes it has small black notches near the tip. • Bare parts. Bill colouration can vary from a grey-green colour to the basai third. becoming yellower towards the tip, to a more creamy-yellow at any stage from late summer to spring, when I see them regularly, though a richer yellow is more often noted by midwinter. The eye often appears dark in comparison with argentatus, but may in close views appear paler, from an amber-yellow to burnt umber (never completely black). The orbitai ring is orange-red. The legs are long, thin and, in winter, commonly coloured very pale (almost whitish) flesh, yellow-flesh or flesh-yellow, paler but brighter than virtually ali argentatus/argenteus and not as obviously yellow as michahellis (though some arrive in autumn with pale, slightly pink-yellow legs). Pitfalls There are many pitfalls in adult plumage and this is one of the hardest plumages to identify. Observers must take very careful notes, plus (preferably) photographs or video, especially if they are inexperienced.

22


Guidelines

for the Identification

of the Caspian

Gull

I hope that the above does not sound too daunting: I have tried to give as much detail, but without over-complicating the picture. There is no doubt the identification of large gulls is very difficult - even very experienced observers admit to this - and the subject is not one to approach lightly. However, there is a growing pool of information and knowledge to help, and as the recent run of records at Minsmere show the birds are out there, so go and watch them and learn. References Jonsson.L., 1998. Yellow-legged Gulls andyellow-legged Herring Gulls in the Baltic, Alida 3/1998: 74-100. Garner, M., and Quin, D., 1997. Identification of Yellow-legged Gulls in Britain, British Birds 90: 25-62. Garner, M.,Quin. D.. and Glover, B.. 1997 .Identification of Yellow-legged Gulls in Britain, British Birds 90:369-383. Harris, A., Shirihai, H, and Christie, D., 1996. Macmillan Birders Guide to European and Middle Eastern Birds. Shirihai, H., 1996. The Birds of Israel, Academic Press, London Mailing Olsen, K., and Larsson, H., 2003. Gulls of Europe, Asia and North America. Helm, London. Collinson, M.. Parkin, D., Knox, A., Sangster, G., and Svensson, L., 2008. Species houndaries in the Herring and Lesser Black-backed Gull complex. British Birds 101 : 340-363. Brian Small

23


Suffolk Birci Report

2007

The Return of Nesting Crânes (Grus grus) to the Fens of Eastern England Summary Two pairs of crânes nested, unsuccessfully, at Lakenheath Fen reserve in 2007; they may well have come from the expanding population on continental Europe. Their foraging areas in summer were partly-flooded reedbed clearings, grazing marsh, setaside and post-harvest cereal fields. Each pair foraged on mutually-exclusive areas of 18 hectares. The inter-nest distance and density corresponded to those of continental studies, One pair, which may have nested within the visitor-zone, moved to a quieter part of the reserve once visitor numbers increased in May. History Crânes bred commonly in East Anglia until about 1600 and. at one time, great flocks occurred in the Cambridgeshire and Lincolnshire fens (Piotrowski 2003). There is no clear evidence that they ever bred in the 30 sq. miles of Suffolk fens. Since 1983 they have occurred in Suffolk almost annually, often involving birds from the small breeding population in the Norfolk Broads. Background to 2007 Between 31 st March and 23rd July 2007, Crânes were seen at 64 locations in the UK, based on reports submitted to the Birclwatching magazine. The locations were within about 29 counties and ranged from the northern tip of Shetland to southern Cornwall and from west Wales to east Kent; reports from locations in east Norfolk were excluded. The majority of locations (50) were east of lines connecting Newcastle-on-Tyne, Liverpool and Bournemouth. Based on the reports, the highest total on one day was 11 in southern England on 29th Aprii but. with five in northern Scotland just three days later, a minimum total of about 20 is more likely. It is possible that some of these crânes came from the population in the Broads of east Norfolk; it's known that some temporarily disperse from there in late winter/early spring. However, some, if not ail. may have emanated from an expanding continental population; for example, the breeding population in Denmark increased from four pairs in 1990 to about 60 pairs in 2006. Based on 212 successful pair-seasons between 1998 and 2006 inclusive, this Danish population produced a mean of 1.58 young (Tofft 2007) or a total of about 40. Tofft considered that the increase in Denmark stemmed from increasing numbers in nearby countries, such as Germany. that, in turn, related to better protection and improved feeding conditions in their winter quarters. If any of these young, continental birds migrated westwards in search of suitable habitat for their first- nesting attempts. they may have been assisted by favourable weather; between about 22nd March and 6th May 2007 there were persistent east or north-east winds and anti-cyclonic conditions over southern Britain and the North Sea. Crânes at Lakenheath Fen A pair of Crânes (pair A) was first seen in late March and they stayed at or near the reserve, or elsewhere in The Fens, until the year-end. Six migrating crânes circled the reserve several times on 18th Aprii but departed. at a high altitude, to the north-east. At about the same time, pair B arrived and stayed until the year-end.

24


The Return of Nesting Cranes to the Fens of eastern

England

Nest areas The two nest sites were 1.200 metres apart. Other studies show that nests are rarely closer than 2-3 kilometres apart (based on habitats in Russia) although nests have been found only a few hundred metres apart where birds flying to their foraging site can avoid crossing other birds' territories (Cramp el al. 1980). In Estonia. 54% of nests were over one kilometre apart and 34% were 500 to 1.000 metres apart (Leito et al. 2005). The nest-site of pair A was an open area within the reedbed. The characteristics of the area were: a perimeter deep-water channel enclosing just over a hectare of land; a reed-fringe along 100% of the perimeter; a 20 cm deep pool (800 sq metres) within the area; damp and dry land over the rest of the area; and an uninterrupted view from the nest of over 100 metres. The plant species on the damp and dry areas included: Sparse Reed (Phragmites australis), Great Water Grass (GlycerĂ­a mĂĄximo), Reed Canary Grass (Phalaris arundinacea), Amphibious Bistort (Persicaria amphibia), Great Reed Mace (Typha latifolia), Celery-leaved Buttercup (Ranunculus sceleratus) and Great Pond Sedge (Care.x riparia). The shallow pool was, even in July, devoid of vegetation. This suggests that the cranes were cropping plants as soon as they emerged from the ground below water. Much evidence was found of cranes having cropped growing reed and great water grass around the pool's margins. The nest-site of pair B was in an open area with patches and fringes of reed nearby. The characteristics of the site were: deep water around 70% of the general, two- hectare, area; 2,300 sq. metres of open, slightly raised land immediately around the nest; reed around 80% of its perimeter; a shallow pool nearby containing plant species similar to pair A's site; and an uninterrupted view from the nest of no more than 50 metres. The site was drier than that of pair A, with grasses Agropyron spp dominant. Pair A certainly laid two eggs and, judging by the behaviour of the adults, young may have survived for about eight days. Possible causes of mortality were predation by Marsh Harriers, Circus aeruginosus, which nested within 100 metres, and 43 mm of rain that fell in a two-day period soon after the latest hatching date. Pair B made a nest but there was no evidence of eggs having been laid or predated. Cranes, even in full breeding plumage, can make a nest and yet fail to lay eggs (John Buxton pers. comm.). Types of foraging sites Between March and September inclusive, the two pairs of cranes used four main types of habitat for foraging: open areas within the reedbed on the reserve, grazing marsh on the reserve, plus set-aside and post-harvest cereal fields beyond the reserve. Open areas within the reedbed are typified by the description of pair A's nest area (see above) but the relative abundance of plant species' varied from site to site. Every site consisted of vegetation emerging from shallow water but as the vegetation height increased with time, so the use by cranes diminished. The grazed pasture on the reserve covers about 28 hectares. The sections used by Cranes were water-logged or shallowly flooded for much of

25


Suffolk Birci Report

2007

the summer, with a cover of Sparse Rushes (Juncus spp), Celery-leaved Buttercup, Creeping Buttercup (Ranunculus repens), Great Willow herb (Epilobium hirsutum) etc., all - except the rushes - grazed by cattle and sheep. The use by Cranes was fairly constant throughout the seven months. The main area for foraging on the agricultural land was an eight-hectare field of, effectively, short-term set-aside (though not in an agri-environment scheme). At the end of May the estimated ground cover was about 60%; a casual survey showed that Mugwort (Artemesia vulgaris) was dominant, with other ruderal species such as Goosefoots (Chenopodium and Atriplex spp) and Annual Nettle (Urtica urens). However, the important food source for cranes was potatoes that had emanated from the remains of a commercial crop of 2004. 90% of the potato plants had tubers attached, some at or just below the ground surface, and cranes were regularly seen eating the tubers (in situ) between May and August inclusive. From late August to the end of September, cranes fed on post-harvest cereal fields, presumably taking spilt grain alongside hundreds of Wood Pigeons and corvids. From October to December inclusive, both pairs remained at or near the reserve for most of the time; on occasion one pair spent several days at other sites in The Fens, such as the Ouse Washes, and pairs seen elsewhere may or may not have been Lakenheath Fen birds. By the year-end both pairs were again regularly roosting within the reserve's reedbeds. The foraging areas from October to December were similar to those of April to September. The principal difference was much less use of open areas of the reedbed perhaps due to the plants being taller and more woody - but with little difference in use of the pasture on, and to a limited degree off, the reserve. Additional habitats used for foraging were areas of maize, recently-drilled cereal crops, ploughed land being prepared for rootcrops and recently-harrowed set-aside land. Extent of foragin° sites Luckily, it was possible to distinguish the two pairs: the two birds of pair A were more or less the same but the individuåis of pair B were noticeably different in size and one was paler. When it was possible to determine the pair (A or B) in the field, and when the birds were clearly foraging. the location was recorded on maps. By super-imposing a hectare grid over the foraging sites it was possible to determine the total area used for foraging as well as per pair and per month. From March to September, each pair used a total of approximately 18 hectares for foraging. Pair A's area consisted of nine hectares of pasture (throughout nearly all months), six hectares of cereal stubble (September only), two hectares of reedbed-clearing (throughout the summer) and one hectare of set-aside in late summer. Pair B was different: five hectares each of pasture and set-aside (potatoes) for much of the summer, six hectares of cereal stubble in autumn and two hectares of reedbed clearing throughout the period. The population density, in more general terms of pairs per square kilometre, conformed to some other reports. The two pairs at Lakenheath Fen occurred within about 170 hectares of apparently-suitable habitat (reed-bed. sedge-bed, pasture, ungrazed fen) where disturbance by humans was almost absent; this is 1.2 pairs/sq km. Arvidsson (in Ratcliffe 2005) found 0.18prs/sq km in Swedish Lapland and Hakala (in Ratcliffe 2005) found 0 . 3 - 1 . 6 pr/sq km in subarctic Finland. Densities as high as 7.5-12.5 pr/sq km have been reported (Cramp et al. 1980). Visitor management The reserve is divided into two zones: the western zone where there is a little-used. public

26


The Return of Nesting Cranes to the Fens of eastern

England

footpath on the northern side, but no internai paths; and the eastern zone where there is more of the northern public footpath (well-used here) plus internai visitor trails. These internal trails amounted to nearly four kilométrés adjacent to approximately 50 hectares of cranes' foraging/roosting/nesting habitat. From late March to mid May the eastern (visited) zone was used by pair B for foraging and roosting but once visitor numbers increased in May they deserted 90% of this zone and moved, to forage, roost and nest, in the western (quiet) zone. Leito et al. (2005) found that, in Estonia. 67% of nests were over 500 metres from the nearest building, road orpath and that only 4% were less than 100 metres away. The former produced significantly more young than the latter. The future With both pairs present at the end of December 2007, it is possible that they will attempt to nest in 2008. However, the size and suitability of the reserve, combined with the internest distance of. typically, several hundred metres may restrict the number of nesting pairs to three or four at most. The large wetland habitats being created in Cambridgeshire should provide better opportunities for a larger population of nesting cranes: a total of over 6,000 hectares at Wicken Fen and Woodwalton/Holme Fen. Much depends on whether nesting cranes are a specific objective (perhaps necessitating specific management) and the extent to which public access is promoted. If done successfully. The Fens of eastern England could once again be the place to enjoy, throughout the year, the distant trumpeting of wild cranes in the home of their ancestors. Acknowledgements Katherine Puttick and Steve Wiltshire also spent many hours watching and recording cranes throughout the year; likewise David Spencer on nearby farmland. John Blackburn, John Buxton, Andrew Grieve, Phil Heath. Steve Prowse and Richard Starling kindly shared their enthusiasm and knowledge of Cranes in The Broads. Granger Harrison willingly put cranes high on his agenda while managing his cattle and sheep on the reserve. Brian Palmer decided to maintain his set-aside field as such, rather than prepare the land for a commercial crop. References Piotrowski, S.H. 2003. The Birds ofSuffolk Christopher Helm, London. Tofft, J 2007. Tranens Grus grus bestandsudvikling i Danmark 1990-2006. Dansk Orn. Foren. Tidsskr 101: 67-72. (English summary). Cramp. S. et al. (eds) 1980. Handbook of the Birds of Europe, the Middle East and North Africa (The Birds of the Western Palaearctic): voi. 2., Oxford University Press, Oxford. Leito, A., Ojaste. I., Truu, J. & Palo, A. 2005. Eurasian crâne nest-site selection. Omis Fennica 82: 44-54 Ratcliffe. D. 2005. Lapland: A Naturai History. Yale University Press, New Häven and London. Norman Sills Site Manager. RSPB Lakenheath Fen nature reserve May 2008

27


Suffolk Birci Report

2007

Changes in a House Martin colony in north Suffolk during 25 years Peter J. Dare Introduction These colonial nesting hirundines, and their hemi-spherical mud-built nests attached below the eaves of rural dwellings, are stili a familiar sight throughout much of Suffolk (Piotrowski 2003). However, House Martins are thought to have been declining over recent decades in many areas of Britain (Wernham et al. 2002) but the extent has not been measurable. except very locally. Ringing in Lincolnshire has shown that birds frequently interchange between neighbouring colonies and villages (Hill 2003, Wernham et al. 2002) and thus pose censusing difficulties. Unlike its Swallow and Sand Martin relatives, the life history of House Martins is not well understood; in fact, this commensal breeder with man is stili a bird of mystery in several respects (Hill 1995). Thus, many aspects of its behaviour and life style resemble more closely those of Swifts than of the other two hirundines. Most notable is the ability of both adults and nestlings to withstand several successive days of bad weather during the breeding season, by using fat reserves and by lowering their metabolism and body temperature to become torpid in the nest until favourable feeding conditions return (Prinzinger & Siedi 1988, Steen et al. 1989). Furthermore, House Martins are generally much higher altitude feeders, mainly on aphids and tiny flies (Bryant 1973, Turner & Rose 1989), than its congeners. Also, unlike Swallows, the fledglings are not fed away from the nest. They differ also by not forming large roosts, either on autumn passage or in winter (Cramp 1988, Hill 1997). Indeed, there is good circumstantial evidence that many birds may roost overnight high in the air, like Swifts, both when in this country and in their winter quarters above the central African highlands and rain forests (Cramp 1988, Wernham et al. 2002). Given these intriguing facts, it was, thus, a privilege to live with and observe, for 25 years, the House Martins nesting on our former house at Henstead in north Suffolk. This paper describes the fortunes and vicissitudes experienced by this colony between 1983 and 2007, and offers some insights into the life style of this fascinating and charming 'summer guest under our eaves'. Spring Arrivais The first returning martins were eagerly awaited each year from mid Aprii onwards. Usually singles, but sometimes a pair, would appear flying up to old nests early on a dry morning between 06.45 and 08.45 BST, though occasionally in late morning ( 10.45-11.30 h) and once in the early evening (19.00 h). Extreme dates were Aprii 17th (2004) and May 19th (1984). In 14 of the 20 years with records the first arrivais were in the last 11 days of Aprii but in five years not until May 12-19th. The average first arrivai date was Aprii 30th (mĂŠdian Aprii 26th). There was often a gap until next birds arrived; colony members would then increase gradually over an extended period of a month or more. In many years probably only half the pairs had arrived by the end of the third week in May. In 2001, when record numbers bred. there was a late influx in June and early July apparently of birds displaced from nearby houses that were being redecorated by the local council. In Lincolnshire also. arrivais may continue into June (Hill 2003).

28


Changes in a House Martin colony in north Suffolk during 25 years

Fig. 1a. House Martins: first arrivai dates, 1 9 8 6 - 2 0 0 7 50 45 S 40 ï

a

35

< 30

2 25 £20 >

S 15 10

y = 0.6323x + 1292.6 R2 = 0.2003

5 •

0 1985

1990

1995

2000

2005

2010

Fig. 1b. Arrivai t i m e s and c o l o n y size that year 45

When first dates are plotted as a time series (Fig. la) it can be seen that there was a slight tendency for birds to arrive progressively earlier in more recent years. However. this was in part a function of colony size (Fig. Ib) though not of breeding numbers in the preceding summer (Fig. le). In other words, the more birds that returned the more likely it was that the first one would be earlier than usual. (An explanation of R2 values is given at the end of this paper). Fig 1c. Arrivai t i m e s and c o l o n y size in the preceding year

;

40 35 30

:

20

•' *

15

y = 0.018x +28.133 R2 = 0.0002

10 y = -0.7376X + 38.24 R2 = 0.2283 5

10

15

20

25

no. of pairs in year n-1

Nest Observations Nests were built on ail four sides of the house but mostly, and about equally, along the lengthier north and south facing aspects. Their structure and inaccessibility under the 20ft high eaves precluded inspections to measure basic parameters such as laying dates, clutch sizes, hatching dates and fledging success. To do so. it would have required something like fibre-optic endoscope probes and innumerable high ladder ascents from soft footings. I was, however, able to note probable hatching dates, by listening for recently hatched chicks calling at dusk or from newly hatched shells dropped beneath nests. From these, approximate laying dates could then be estimated by back-dating using an average incubation period of 15 days (Turner & Rose 1989). Actual fledging dates and departures could be observed directly. Old nests were occasionally taken over by other bird species. In addition to House Sparrows in the early years, a pair of Spotted Flycatchers reared young in a half-built nest in 1985 and 1987 after ousting the rightful owners. In the latter year, the martins reclaimed their nest after the flycatcher brood had fledged. A pair of Blue Tits nested successfully in 2004 and 2005 while two other nests provided winter roosts for a Wren and Blue Tit. Annual Variations in Colony Size Although three pairs were already breeding when we moved into the Henstead house in 1983, the first observations were not made until 1987 when there were 5 pairs that fledged a total of only 6 broods, owing to interference from two pairs of House Sparrows usurping nests. Subsequently (Fig. 2), the colony fluctuated erratically between four and 11 pairs

29


Suffolk Birci Report

2007

until 1998 after which numbers rose rapidly to peaks of 21 and 22 pairs in 2000-01 and again of 20 and 22 pairs in 2004-05. Sadly and inexplicably, the colony then declined rapidly to only eight pairs in 2007.

Fig. 2. House Martins: numbers of 1 st (black), 2nd (bars) and 3rd (chequer) broods reared each year, 1987-2007 25

20 -

15 -

10

-

5 -

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

House Martins also nested annually, but in small and variable numbers, on several other dwellings around the village. Their numbers gradually increased roughly in parallel with those in our colony. Thus, from about 12 pairs at five sites in the 1990s, numbers had risen to c.28 pairs (ten sites, four pairs in artificial nests) by 2005 - when 22 pairs were nesting on our house. Numbers then fell sharply in 2007. In many of these years our colony was almost certainly the largest within a 10km radius. Breeding Season The martins, as elsewhere, had a five-month season lasting from May through well into September with many pairs rearing two broods each year. The timing and duration of the season varied between years, largely according to the arrivai patterns and to the highly unreliable availability of mud for nest repairs or building new nests. In most years, birds brought mud from a farm lane 250m away or from irrigated fields closer to the house. During spring droughts (not uncommon here) martins readily made use of mud 'wallows' provided in the garden or by watering scrapes dug into the adjoining beet and potato fields (Dare 1996). Exceptionally, given ample mud close by. one new nest was built by a pair in only four or five days. In most years there were unclaimed nests from previous years. Early birds returning to undamaged nests apparently started laying in mid May whereas late-comers or any awaiting suitable mud conditions began 2-3 weeks later. This often led to considĂŠrable overlaps between early hatching and late laying pairs, most notably in

2006. Based on dates when tiny chicks were first audible, the first clutches hatched during June 8th-25th in 14 recorded years. The average first date was June 15th and the mĂŠdian June 12th. These dates would indicate that first eggs had been laid probably between May 20th and June 7th; as estimated from back-dating based on an average clutch of four eggs and

30


Changes in a House Martin colony in north Suffolk during 25 years a 15-day average incubation period from the last egg (Bryant 1979. Cramp 1988. Turner & Rose 1989). The corresponding average and médian first-egg dates would have been May 28th and May 25th respectively. lt should be noted that 'incubation may be prolonged by bad weather when the adults leave eggs unattended for long periods' (Turner & Rose 1989). The first broods of young martins started to leave their nests between June 25th and July 20th in the 10 years when exact dates were recorded. One brood was observed fledging between 11.00-11.15 am on a fine morning though most flew much earlier in the day. The mean and médian of first fledging dates were both on July 12th. which indicates a nestling period of 27-30 days (mean and médian). Extreme values for individuai nests varied in différent years from 17 days (in 1998) to a remarkable 34 days (in 1994 and 2007). Bryant (1978) quoted a range of 22-32 days, such high variability depending partly on brood size and it may be lengthened in bad weather. The sizes of successful broods at Henstead could not be measured accurately but 2 or 3 fledglings appeared to be the norm; one brood of 4 was counted leaving its nest. Fledglings were never observed to be fed by their parents unless they had returned to their nest. This they did for several days until strong on the wing, at which point, and despite there being unused old nests available, they departed. Some adults also abandoned the colony around this time leaving a variable proportion behind to lay second clutches. Thus, there was often a considérable réduction in colony size during late July and early August. Where these birds went remains a mystery; perhaps they began their autumn migration? The last of the second broods typically fledged between September 16th and 27th, but in the very bad summer of 2007 the only pair to breed twice fledged their last young on August 23rd. The very latest fledging date, for the only third brood to be recorded. was on October lOth in 1995. Breeding Success Annual fluctuations in the colony size and its overall breeding performance are shown in Figs. 2 and 3). Successful pairs raised mostly two or three fledglings per brood from normal

Fig. 3. House Martins: annual numbers of pairs (large square) and broods fledged (small Square), 1987-2007

o 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

31


Suffolk Birci Report

2007

clutches of probably 4-5 eggs (Campbell 1972, Harrison 1975). Nesting success was high; 93.2 % of first clutches producing flying young; similar to the 90.4% value recorded in a 5-year Scottish study (Bryant 1979). A highly variable proportion (0-89 %, average48.5 %) of pairs also reared a second brood in their same nests while an exceptional third brood was fledged from the one nest in early October 1995. This was similar to the output by colonies in Lincolnshire (Hill 2003) whereas a higher incidence of second broods (76.5%) was observed in Scotland (Bryant 1979). At Henstead, there was a slight tendency for the proportion of second broods to be greater at larger colony sizes than when only a few pairs nested (R 2 = 0.1133, n = 20). On the other hand. even when the colony was thriving there were striking différences between successive years. Thus, when 19 pairs bred in both 2004 and 2005 there were 11 (58%) and three (16%) second broods attempted, respectively. As a resuit, each pair reared on average 1.41 broods in a summer though this varied considerably; from 1.72-1.89 broods in the four best summers (1997, 1999,2002,2006) to only 0.63-1.00 in the four poorest years ( 1991, 1996,2005,2007). There was no corrélation between colony size and the average individuai performance of pairs (R 2 = 0.0386, n = 20). Possible reasons for annual variability will be discussed later. There was also no corrélation between colony size and breeding success in any given year with the number of birds returning to breed the following spring. Causes of Mortality Total loss of a brood was uncommon; in 12 of 20 years ali first clutches produced fledglings and only 6.8% of ali first clutches failed. By far the two worst years were 1996 (37.5% failed) and 2007 (67.5% failed). Repeated periods of bad weather in late May and early June of 2007, when parents were confined to nests for 1-2 (exceptionally 3 successive) days, caused many complete brood losses. Many local Swallow broods were also lost at this time (C. Carter, pers.comm.). Successful broods could also suffer partial losses within nests. Some nestlings died very soon after hatching, as evidenced by finding three mummified corpses under nests, two when martins were 'spring cleaning' the following year and one between broods. Only one occupied nest collapsed, with three nearly-fledged young inside but these were rescued, fed and flew several days later. In his Scottish colony, Bryant (1979) noted that whole brood losses were unusual (0% of first broods. 4% in second broods) and only 3-4% of chicks died in partial brood size réductions. The first flight was also a very criticai time for broods - there were no second chances for unfit youngsters (whereas Swallow fledglings normally have perches beside their sheltered nests). At fledging time. a total of 12 young martins were found beneath nests or after crash-landing on lawns. Of these. 7 (2 runts) were dead or dying and 5 (3 runts) were rescued. Four of the last group were placed in the nearest nests while a full-grown youngster flew strongly from the hand. One runt had fallen as its siblings fledged and departed with their parents. Eight of these casualties happened over a short period in 2005 after repeated spells of bad weather: several youngsters were clearly too weak to fly back up to their nests. In contrast, only three parents are known to have died at the colony, ail from accidents orectoparasites. One fell beside me with abroken wing.having just collided with something, and another was found hanging dead from a nest with its foot entangled in nest material after a fight with an intruding martin. The third bird was infested with a bloated tick below one eye and a large Crataerina hirundinis flat-fly in its plumage. Bryant (1979) had also found that adult mortality was well below 5% in his colony of 30 pairs in which only one bird was known to have died during 5 breeding seasons. Predators: Prédation losses were low despite regular sightings of Sparrowhawk and Hobby over or in the garden. The Martins' early-warning system was very effective in

32


Changes in a House Martin colony in north Suffolk during 25 years alerting the colony (and me) to the presence of these raptors. In 2005 and 2006 a maie Sparrowhawk made several attempts to catch birds emerging from nests by flying swiftly along beneath the eaves or by swooping up from low level. It was suspected to have been successful on one occasion. Birds from the local Hobby pair frequently over-flew the colony in late summer but attacked only once; when an adult stooped spectacularly into the garden close to the house while narrowly missing contact with tree branches, téléphoné wires and the ground. Final Autumn Departures The occupation period of the colony each year varied widely from 119 day s ( 1991 ) to 170 days (1995) and averaged 148 days duration in 18 years. Not surprisingly. the duration of stay tended to be longer when the colony was largest in the later years ( R : = 0.1588, Fig. 4a). Fig. 4a. House Martins: c o l o n y size and stay

Fig. 4b. House Martins: last departure dates,

duration

1987-2007 50

170160 S

5 40

S

150

S 140 3 130

0) a V

«

«

20

E

o » 10

120 110 100

-O E 30

'

y = 0.9373X + 136.53

y = -0.3943x +811.87 R2 = 0.0437

R 2 = 0.1588

5

10

15

20

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008

25

no. pairs

-10

Birds that had reared early second broods started to leave during late August and early September within days of the young fledging. The latest broods of the season usually went with their parents on the morning of their first flight in late September or early October, the latest being by a third brood on October lOth. There was no long term trend in the final departure dates (R 2 = 0.04, Fig. 4b). In October of one or two years I noted a few autumn passage birds dropping in to roost for a night a week or more after the last breeders had gone. Discussion With their highly aerial life style and trans-equatorial migrations. House Martins should be especially vulnerable to vagaries of weather in ali seasons. This has been confirmed by the Henstead colony observations and from perusing the limited literature, as will be noted below. The first arrivai dates of our summer visitors have been eagerly recorded each spring in Suffolk and elsewhere for decades and then logged in county reports. Analyses of such lengthy time series have indicated that some species may be tending to arrive earlier nowadays (Sparks 1999). In Suffolk since 1950, the mean first arrivai date for House Martin has been Aprii 2nd though with wide variability between years (Croxton & Sparks 2005). This date is more than three weeks before the median first date at my colony. These authors have further estimated that first dates since 1970 have become earlier by an average 9.9 days.compared with the pre-1970 period. It is therefore interesting to note a similar if slight tendency by the House Martins at Henstead though this could at least in part have been linked with changes in colony size (Fig. lb). It should also be cautioned that, given the protracted and variable arrivai pattern of the colony each spring, conventional first dates

33


Suffolk Birci Report

2007

(many probably relating to passage birds) are probably an unreliable indicator of changes in population phenology. They are also liable to be biased by the huge increases in observer effort since the 1970s. A more meaningful indicator would be to use the date by which (say) 50% of birds had returned, though that would require more effort to measure. The considérable annual changes in the size of the Henstead colony (Fig. 2) were typical of martins,even over an area as large as the 150 km 2 rural district surveyed in Lincolnshire (Hill 2003). These fluctuations are caused by a range of man-induced and naturai factors. The former involve localised influxes of birds displaced by human disturbance (house maintenance and nest destruction) as happened elsewhere at Henstead in June-July 2001. Naturai factors include variable nesting behaviour (site fidelity) and, more importantly and over wide areas, weather related impacts on breeding success and subséquent survival overwinter in Africa and during return spring migration. For example, between-years fidelity to a spécifié colony varies (as shown by ringing and retrapping studies) with the âge and sex of martins. The intensive Lincolnshire study (Hill 2003) showed that virtually ail (88%) surviving breeding maies returned in the next year to their colony or (98%) to one within 5km whereas breeding females were rather less faithful (75%) to their former sites. First-time breeders returned to the same general area of birth (98% of maies, 86% of females) but were much less faithful to their actual natal colony (49% and 18%). In other words, colony size in any year depends mainly upon the survival of adult (more especially niale) breeders from the previous year and much less upon the previous breeding success. This could explain why good breeding seasons at Henstead were no guarantee of high numbers the next year. In addition, House Martins experience high annual death rates; estimated as being 57% for adults in a Scottish colony (Bryant 1979) and ranging from 36-67% in Continental countries (Cramp 1988). As at Henstead, extremely few adults died in the breeding season at the Scottish colony. Juvenile or first-year mortality is perhaps as high as ca. 80%. Large mortalities have been recorded in African winter quarters during adverse weather (unseasonal rain and cold); estimated ca.20 000 birds died in one such incident (Wernham et al. 2002). Losses during spring migration, though unquantifiable, could be sufficient in particular years to explain sudden large year-to-year falls in breeding numbers in Britain. Thus, a fall nationally (and at Henstead, Fig.2) in 1991 was attributed to adverse conditions in the western Mediterranean basin that spring (BTO News no.176, Hill 2003). Grounded and dying martins were found in northern Morocco, just after their Saharan crossing, during cold weather in one Aprii during the 1960s by BTO ringers (BTO report). In fact, periods of inclement weather are not unusual over the Gibraltar Strait and southern Iberia during Aprii though the effects of these migration hazards on annual arrivai patterns and numbers of common species in Britain are yet to be assessed. Weather factors at Henstead undoubtedly affected the outcome of some seasons' breeding attempts. Poor feeding conditions, as most strikingly in 2007 (Figs. 2 and 3), could lead to above average losses among first broods and then lower the proportion of pairs attempting second clutches. Delayed arrivais of many pairs in other years, perhaps related to bad weather en route, likewise could have precluded them from breeding twice. Finally, our always busy Martins at Henstead were fascinating to watch, while listening to their cheery burbling courtship songs in nests provided a delightful dawn chorus. They also often indulged in fierce squabbles between nest owners and intruders, adults or novice fledglings, trying to enter the wrong nests. In fine weather at the height of the season their activity was non-stop from dawn to dusk, with up to a dozen parents simultaneously bringing in food to their noisy broods. Their flight paths then often criss-crossed at high speeds in a bewildering pattern around the house. There were. however, also anxious times; as when

34


Changes in a House Martin colony in north Suffolk during 25 years trying to replace fallen fledglings into nests or wondering, as in 2007, whether broods and parents could survive prolonged bad weather. Given what 1 have gleaned from the sparse literature about House Martins, I now have a much greater understanding and appreciation of these still mysterious summer guests who chose our abode for their colony. With their final departure each autumn the house and garden suddenly fell eerily silent. It was then high time for me to concentrate on sea-watching once more! [Explanatory note: R 2 has a maximum value of I. when all data points fall on a straight line, i.e. the relationship between two variables (say. arrival dates and years) is perfect and hence 100% of the change in arrival dates is related to the passage of time (years). Thus, in Fig.la, if all first dates of martins had fitted a straight trend line then we would be 100% certain that birds were arriving progressively earlier every year. Conversely, when data points are more variable (scattered) the values of R 2 become smaller, i.e. a smaller percentage of arrival date changes can be time related. The very low R2 values in this study (0.2 or less) show factors other than time per se were more important in producing the trend or tendency.] References Bryant, D.M. (1973). Factors influencing the selection of food by the House Martin (Delichon urbica (L)). Journal of Animal Ecology, 42: 539-564. Bryant, D. M. (1979). Reproductive costs in the House Martin (Deliclion urbica). Journal of Animal ecology, 48: 655-675. Cramp, S. (ed.). The Birds of the Western Palearctic, vol. 5. Oxford University Press. Croxton, P. & Sparks, T.H. (2005). First and last dates of migrant birds in Suffolk 19502004. Suffolk Birds, 55:16 -23. Dare, P.J. (1996). Mud for Martins. Suffolk Ornithologists Group, The Harrier, 109: 18-19. Hill. L.A. (1995). The mysterious House Martin. Safring News 24: 79-80. Cape Town. Hill, L.A. (1997). Trans-Saharan recoveries of House Martins Delichon urbica, with discussion on ringing, roosting and sightings in Africa. Safring News 27: 7-12. Cape Town. Hill, L.A. (2003). A seven year study of House Martins in Lincolnshire. Lincolnshire Bird Report 2003. Piotrowski. S. (2003). The Birds of Suffolk. Christopher Helm. London. Prinzinger. R. & Siedle. K. (1988). Ontogeny of metabolism, thermoregulation and torpor in the house martin Delichon urbica (L) and its ecological significance. Oecologia, 76: 307-312. Sparks. T.H. (1999). Phenology and the changing pattern of bird migration in Britain. International Journal of Biometeorology, 42:134-238. Steen. J. Bâ&#x20AC;&#x17E; Krog, J. 0 . , T o y e n , 0 . & Bretten, S. (1989). Poikilothermy and cold tolerance in young house martins (Delichon urbica). Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology, 159: 379-382. Turner, A. & Rose, C. (1989). Swallows and Martins. Christopher Helm. London. Wernham. C.V., Toms, M. P., Marchant, J. H., Clark, J. A., Siriwardene. G.M. & Baillie, S. R. (eds). (2002). The Migration Atlas: movements of the birds of Britain and Ireland. T. & A.D. Poyser, London. (Dr. PJ.Dare, 2 Corn Hill, Back Road, Wenhaston. Halesworth, Suffolk. IP19 9BW) [Postscript: Following our move to the above address in November 2007, the Henstead colony was destroyed by the new owners in early spring 2008. Some birds probably were able to relocate by joining others on nearby houses in the village.)

35


Suffolk Birci Report

2007

Marked decreases of some migrant passerine breeders in the Walberswick/Dunwich Forest area in 2007 David

Pearson

DĂźring spring and early summer of 2007 I resurveyed selected breeding passerines at Walberswick/Blythburgh/Dunwich Forest, covering the same area of approximately 20 km2 surveyed in 2002-2004 (Pearson 2004), 1994-1999 (Pearson & O'Dowd 1999) and much earlier last Century (ref. Waller 1980, Pearson 1973). This area is bounded to the north by the R. Blyth, to the south by the Westleton-Dunwich road and to the west by the WestletonDunwich road. Methods and coverage compared closely with those of other years between 1994 and 2004 (for detail see Pearson & O ' D o w d 1999). Singing/territorial birds were mapped during early mornings between late April and mid May, and again between late May and mid June. Sites and routes were visited at least once each period; some being checked a number of times. Striking decreases were noted in three common migrants in particular. There were substantial losses of Willow Warbier and Nightingale from the woodlands, and most of the Sedge Warbiers had disappeared from Westwood Marshes. Despite exceptionally warm April weatherthe arrivai of many migrants was surprisingly late. Then cool and very wet conditions prevailed from late May onwards. But results were not thought to have been greatly influenced by these atypical conditions. Counts for 12 summer migrants are given in Table 1, and compared with counts in 1999,2002 and 2004. Figures are also added for four resident species of special interest. Table 1. Counts of territorial birds in the Walberswick/Dunwich Forest area in 2007 and some other recent years Woodlark Lullula arborea Tree Pipit Anthus trivialis Stonechat SaxĂ­cola torquata Redstart Phoenicurus phoenicurus Grasshopper Warbier Locustella naevia Cetti's Warbier Cettia cetti Reed Warbler Acrocephalus scirpaceus Sedge Warbler Acrocephalus schoenobaenus Whitethroat Sylvia communis Lesser Whitethroat Sylvia curruca Garden Warbler Sylvia borin Blackcap Sylvia atricapilla Dartford Warbler Sylvia undata Willow Warbler Phylloscopus trochilus Chiffchaff Phylloscopus collybita Spotted Flycatcher Muscicapa striata nc = not eounted. Major 2007 changes in bold.

1999 30 16 6 3 18 0 c425 141 143 18 95 173 2 212 147 4

2002 16 7 9 3 nc 1 nc 135 162 16 59 161 15 130 150 2

2004 20 1 6 1 10 6 to 8 c400 125 138 27 102 156 26 109 168 0

2007 17 1 6 0 5 25 c250 76 88 11 82 149 15 73 130 0

Willow Warbiers were already down from over 200 territories in 1999 to 109 in 2004, but had declined further by 2007 to just 73 (Maps 1 and 2). The species is now absent from many of the woods and most of the sallow-fringed marsh edge where it was common ten years ago, and confined mainly to a few small pockets of young birch. Its fortunes contrast with those of Chiffchaff, Blackcap and Garden Warbier whose numbers have held up well despite loss of habitat in the maturing pine plantations of Dunwich Forest. Nightingale numbers had halved in 2007 compared with those of 2002-2004. This may be partly explained by a loss of thicket habitat from the growing deciduous fringes of the forest.

36


Decreases of migrant passerine

breeders in the Walberswick/Dunwich

Forest

However, numbers were down in ail areas. with only eight singing birds on Walberswick NNR compared with 30 in 1999 and 18 in 2004. Whitethroats were late to arrive and the eventual count was also well down on that of other recent years. Ali three migrant marshland warblers showed an overall decrease in 2007. Sedge Warblers were down by over 45% from 1999 numbers. This is due to a continued drastic decline on Westwood Marshes, where the count fell from 143 territories in 1999 to 55 in 2004 and just 21 in 2007 (see Maps below). By contrast, numbers appear to have changed little elsewhere. Around the southern edge of the Blyth grazing marshes for instance 32 territories in 2007 compares well with 39 in 2004 and 28 in 1999. Reed Warbler numbers had declined less dramatically, but were well down in eastern and southern parts of Westwood Marshes. Grasshopper Warblers had decreased greatly and seem to have vacated their former stronghold in the upper part of Westwood Marshes. The few reelers are now to be found in areas close to the shore.

Sedge Warbler 1999

Sedge Warbler 2007

No breeding Redstarts or Spotted Flycatchers were found in 2007 and a single singing Tree Pipit on recent replanting in Dunwich Forest compares with a count of 16 territories in 1999. These three migrants have been virtually lost to the area during the last decade. Among resident species, Cetti's Warblers reached their peak to date, with 24 singing males counted between Westwood Marshes/Dingle Hills and Walberswick village. Dartford Warblers on the other hand were somewhat below 2004 numbers, both on Westleton Heath and at two small colonies at Walberswick. Woodlarks maintained their numbers on the heathland, but with only two singing within Dunwich Forest. Although described by Piotrowski (2003) as Britain's commonest summer visitor, the Willow Warbler has declined in much of England over the last few decades. Losses have been greatest in the east, where BBS results showed a 51 % decrease between 1994 and 2006 (Raven et al. 2007). In northeast Suffolk it has largely disappeared from farmland and is now confined mainly to young growth, especially birch, on sandy soils. Its recent contraction at Walberswick presumably represents a continuation of this trend, and the locai future of this species appears very uncertain. The decreased Nightingale numbers in prime coastal habitat may also be cause for concern. It remains to be seen whether this is a temporary drop from a locai peak at the turn of the Millenium or part of a more serious declining trend. This species does not appear to have decreased in England overall since 1994 (Baillie et al. 2007).

37


Suffolk Birci Report

2007

Sedge Warbler numbers seem not to have changed significantly in Britain over the past decade (Baillie et al. 2007) and for eastern England in particular BBS results show a 10% increase (Raven et al. 2007). The depletion of this species in Westwood Marshes is not mirrored by a similar trend elsewhere in the Walberswick area. It is presumably due to local habitat changes which might also account for a loss of Grasshopper Warblers from the same site. Increasing numbers of deer have modified the vegetation around the marsh edges and groups of Red Deer are frequently seen deep within the wet reed-beds. But more significantly perhaps, spring water levels have been held higher in these reed-beds in recent years to benefit the Bittern and other water birds. This is likely to affect nesting in some of the marshland passerines, including the Sedge Warbler. References Baillie, S.R. et al. (2007). Breeding Birds in the Wider Countryside: their conservation status 2007. BTO Research Report No. 487. BTO, Thetford. Piotrowski, S. 2002. The Birds of Suffolk. Christopher Helm, London. Pearson. D.J. 1973. Changes in the status of heath and marshland breeding birds in the Walberswick area, 1953-1972. Trans. Suffolk Nat. Soc. 16, 152-157. Pearson, D. 2004. Breeding birds of the Walberswick NNR, Hen Reedbeds, Dingle Reserve and Dunwich Forest area of coastal Suffolk, 2004. Report for English Nature, the RSPB and the Suffolk Wildlife Trust. Pearson. D. & O ' D o w d . B. 1999. A survey of breeding birds of the Dingle Resen'e, Walberswick NNR, and Dunwich Forest area of coastal Suffolk, 1999. Report for English Nature, the RSPB and the Suffolk Wildlife Trust. Raven, M.J., Noble, D.G. & Baillie, S.R. (2007). The breeding bird survey 2006. BTO Research Report No. 471. BTO, Thetford. Waller, C.S. 1983. Status changes of breeding birds of the Walberswick area 1973-1982. Suffolk Birds 1982,58-62. David Pearson

38


Suffolk Birci Report

2007

Breeding Ringed Piover in Suffolk, 2007 Mick Wright Summary There has been a catastrophic decline in the number of breeding Ringed Plovers of around 77% when compared to the figures from the last major survey in 1984. A comprehensive search of ail coastline and suitable estuarine habitat found only 43 pairs at 22 locations. The Orwell estuary held the highest number of pairs. Ail pairs were found breeding on coastal or estuarine sand/shingle habitats; none were found inland on Heathland or agricultural sites. Another very worrying observation was that very few Ringed Piover chicks fledged, in fact, only four or possibly five chicks were reported to have fledged. If we are to have Ringed Plovers breeding on our beaches, in the future, then drastic action is required. Introduction The Ringed Piover is now on the Birds of Conservation Concern Amber list, and given that the UK and the Republic of Ireland together hold around 80% of the temperate breeding population of the nominate race of this species, it is clearly important that the national population is monitored on a regular basis. In the breeding season of 2007 there was a full national survey of this species, the first since 1984. The main objectives of the 2007 survey were to obtain a new population estimate, assess their current distribution and to establish current habitat usage. In Suffolk, the survey covered the entire coastal strip, tidal areas of estuaries and a number of inland sites. In addition, a number of random inland and coastal areas were selected to be surveyed. This paper documents the findings for Suffolk. Survey Methods The survey was carried out to tetrad level; maps were provided on which to record observations. T w o visits were required. the first between Aprii I5th-May 14th and the second between May 15th-June 30th to count adults present and estimate the number of breeding pairs. The habitat in which the Ringed Piover were found was also recorded. Results A comprehensive search of ail coastline and suitable estuarine habitat for breeding Ringed Piover found only 43 pairs at 22 locations. Of these 70% (thirty pairs) were found at just five sites, which were the Orwell estuary, Orford Ness. Landguard, Erwarton (River Stour) and Minsmere (see Table 1.). Ail pairs were found breeding on coastal or estuarine sand/shingle habitats, none were found inland on Heathland or agricultural sites. None were found on the random sites. (See Appendix I for full list of results.) Table 1. Number of Ringed Piover Pairs at Kev sites Site Pairs Orwell estuary 10 Orford Ness 8 Erwarton Bay 4 Landguard 4 Minsmere 4 Total 30

39

Locations 4 7 1 1 1 14


Suffolk Birci Report

2007

The results, when compared with those from previous surveys, show that the Ringed Piover, as a breeding bird in Suffolk, is clearly in trouble. There has been a catastrophic decline in numbers of around 77% when compared to the figures from the last major survey in 1984 (see Table 2). Table 2. % Change between Surveys Year Pairs % Change 1979 1979 223 1984 183 18% 2007 43 80%

% Change 1984

77%

Discussion The Ringed Piover breeds widely on the coastal beaches in Britain. Many of the favoured breeding habitats are under intense pressure from man's leisure activities, consequently, the aims of the first national breeding census in 1979 was to assess population levels and to provide baseline information from which future trends and distributions could be determined (Prater 1979). By 1984 we were already seeing a serious decline in the number of breeding pairs on beaches, down by 25% from 164 pairs in 1979 to 125 pairs in 1984. However, at that time Ringed Piover were breeding in various other habitats, i.e. adjacent to coastal or estuary fîelds, industriai areas and inland at gravel pits, heathland and reservoirs. Here, also, we see déclinés in breeding Ringed Piover numbers between the 1979 and 1984 surveys; industriai areas down by 73% and inland sites down by 43%. Only on fîelds adjacent to the coast and estuaries was there an increase of 31% (see Table 3 for summary). In the main breeding areas in 1984, Ray Waters (1985) concluded that "ai our largest Ringed Piover colonies, space is becoming limited due to the increased number ofvisitors, causing a decline in numbers." The message was clear after the 1979 and 1984 surveys that recreational activities in breeding areas was cause for concern and this has overwhelmingly been borne out by the results of the 2007 survey. Table 3. Summary of Breeding Habitats for the Years 1979,1984 and 2007 Habitat 1979 1984 2007 164 Sand/Shingle 125 43 Saltmarsh 16 15 Adjacent Fields 18 26 Industriai Areas 11 3 Other 6 _ Inland 14 8 - = No records received Another very worrying observation was that very few Ringed Piover chicks fledged. Although fieldworkers were not asked to prove breeding, most pairs found were on nature reserve beaches or areas where Wardens and fieldworkers regularly visited. The feedback was that breeding success was low or non-existent. In fact. only four or possibly five chicks were reported to have fledged. On Orford Ness no chicks fledged from eight pairs, yet this site was nationally important in 1979 and held the fourth largest concentration in Britain (Piotrowski, 1980). At Landguard, four pairs had about ten clutches between them but were only able to fledge one chick. The warden said that this was a miracle given the number of dogs that daily run free over the site despite wardening and appropriate

40


Breeding Ringed Plover in Suffolk,

2007

signage. Three chicks fledged on the new shingle island in the Orwell estuary adjacent to Trimley Marshes reserve and possibly one other from within the Little Tern enclosure at Minsmere. The number of people accessing our coastal beaches and estuary shoreline has increased dramatically in recent years and is set to increase still further. One of the commonest forms of recreation is exercising dogs, which in most cases are not on a lead. It is also an activity which is habitual. Disturbance by people and by dogs running free were reported from almost all locations and by most observers. There are clearly no measures in place to control recreational activities in sensitive places or to ensure that dogs are kept on leads. It is blatantly apparent that too many people ignore signage. The possibility that only four or five Ring Plover chicks fledged is very worrying. If we want Ring Plovers breeding on our beaches in the future, then drastic action is needed now. Acknowledgements Many thanks to the following birdwatchers who gave up some of their valuable time to help with the fieldwork for this survey: Dean Backhouse, Adam Burrows, Jon Chapman, Karen Coates, Joe Davis, Malte Eden. Reg Etheridge, Adam Gretton, John Glazebrook, Robin Harvey, Colin Jakes, Trevor Kerridge.Rob Macklin.Mike Marsh, Nick Mason, Alan Miller, Nigel Odin, Tom Oliver, Steve Piotrowski, Derek Rothery, Rick Vonk, Malcolm Wright and Mick Wright. References Piotrowski, S. (1980) Suffolk Ornithologists' Group March-April 1980 Bulletin pp. 1-9. Prater, A. J. (1976) Breeding Populations of Ringed Plover in Britain. Bird Study Vol. 23 pp. 155-161. Waters, R. (1985) BTO Breeding Ringed Plover Sun'ey 1984. Suffolk Ornithologists' Group Summer Bulletin 1985 pp. 12-18.

41


Suffolk Birci Report

2007

Suffolk Spotted Flycatcher Survey, 2007 Introduction Once a denizen of mature gardens, churchyards, orchards, parkland and woodland edge, the distribution of the Spotted Flycatcher Muscicapa striala in Suffolk seems now to be very much confined to the vicinity of human settlements with few pairs being located in farmland and woodland. Its tendency to use ledges and niches in dwellings and other buildings for a nest site gave this popular bird the old Suffolk nickname of Wall-bird. Nationally, the Spotted Flycatcher's population has declined critically since the 1960s. The combined results of CBC and BBS surveys indicate a rĂŠduction by 84% during 1967-2005 in the UK, and by 87% in England as a whole. It is consequently a Red List Species of Conservation Concern. The distribution map for Spotted Flycatcher in Birds of Suffolk, using data up to 1997, shows it to be widely scattered across the county. But by 2000 the first signs of a retrenchment were appearing, with only three singing maies at Minsmere compared to nine the previous year, and only 12 sites in the county reporting having flycatchers. This subsequently improved with 18 sites in 2001, 25 sites (one with five pairs) in 2002, 24 sites in 2003 and 27 sites in 2004, by which time the species was rarer on the coast and being reported predominantly front the west of Suffolk. Although some 45 pairs were recorded in 2005, predominantly in large village gardens. the flycatcher's decline was indicated by its occurrence in only 4% of BBS squares compared with 24% in 2000 and 30% in 1995. Its status seemed to recover during 2006 when many more records were received than usuai, notably from the west, and a total of 99 pairs of Spotted Flycatcher were known to exist in Suffolk. In 2007 Suffolk Ornithologists Group with Suffolk Wildlife Trust organised a survey specifically to obtain a more accurate picture of the Spotted Flycatcher's current status in the county. For a bird that is readily identifiable this would rely as much on the observations of the public as those of regular contributors to the annual bird report. Two local surveys of Spotted Flycatchers during 2006, around Framlingham and Hadleigh, had demonstrated the value of using community newsletters and a town website to obtain records. The Survey The survey was launched publicly at Parham Village Hall on 8th May. Its aim was to determine the distribution and number of breeding pairs of Spotted Flycatcher in Suffolk. The joint organisers used their respective journals, the SWT website, posters, parish magazines and the media to advertise the survey priorto the breeding season and to appeal to both members and the public for observations of Spotted Flycatchers. A fact sheet and standard survey form were produced which requested data in two catĂŠgories of importance. 'Essential' covered location, habitat and dates of breeding activity. 'Useful' provided the opportunity for nest records including site, clutch size and fledging success. The survey drew much public interest and there was a gratifying response to its appeal for records. Results Records were received from 209 sites across Suffolk of which 153 definitely or probably refer to breeding pairs of Spotted Flycatcher. As can be seen from the resulting plot of ail the records below (Fig 1), most sightings came from the east of the county which is contrary to the trend reported in previous years. However further records submitted to the county recorders partly redresses that balance. The open circles on the map show this phenomenon. The majority of flycatcher records (84%) came from village and town gardens, although observer bias cannot be discounted. Walls, mainly of houses with climbing shrubs or ledges. were the most favoured nest sites, with a few being located in pergolas, trees and open sheds (Table 1 ). Almost none used open-fronted nestboxes or the empty half-coconuts that are

42


Suffolk Spotted Flycatcher

Survey,

2007

secured in climbers or ledges and which have been readily adopted by flycatchers elsewhere. Otherwise, the distribution was churchyards and similar (9%), copses and orchards (4%) and farms (3%). Spotted Flycatcher

Productivity data were too incomplete for analysis, but there was a broad indication of clutch size and fledging success being normal despite the inclement summer weather. Table 1. Nest sites in gardens House climber Hanging basket/pot House ledge/light Nestbox/half-coconut Outbuilding wall Tree Pergola Open shed beam Unspecified Total

31 4 5 4 15 2 2 4 21 88

Discussion Various factors have been posed for the decline of the Spotted Flycatcher in Britain: cool weather during the early part of its nesting period, heavier nest predation by grey squirrels, cats and corvids, the deterioration of woodland quality due to lack of management and, of particular relevance to Suffolk, a reduction in insect food by agricultural pesticides. However, population modelling using data from BTO studies has shown that a decrease in first year survival rates may have driven this decline. There has been no significant change in clutch and brood sizes. The poorer survival rate has been a constan! factor across the country including the west where Spotted Flycatchers are still using farmland and woodland.

43


Suffolk Birci Report

2007

suggesting that the cause lies elsewhere. The flycatchers are quite possibly encountering degraded habitat, drought and a heavier use of pesticides both in their southern African winter quarters as well as on migration. Without a previous county wide survey to compare with this one it is difficult to quantify the supposed decline of Suffolk's Spotted Flycatcher population. However, when adding the reports of other nesting sites made to the county recorders, it is estimated that Suffolk had at least 200 pairs nesting in 2007. Acknowledgements To Steve Piotrowski of Suffolk Ornithologists Group for devising the survey, to Oka Russell of Suffolk Wildlife Trust for distributing and collating the survey forms and to the many flycatcher enthusiasts for reporting their birds in response to the widespread Publicity. Anthony Chapman,

17 Lambert Close, Framlingham.

44

Woodbridge. 1P13 9TE


Suffolk Birci Report

2007

The Barnham Goosanders: A New Breeding Bird for Suffolk The Goosander is described in "The Birds of Suffolk " (Piotrowski 2003) as a locally common winter visitor and passage migrant and in "The Birds of Norfolk" (Taylor et al. 1999) as being rare in summer. I was therefore more than surprised when on June lst 2006, whilst walking along the River Little Ouse in Barnham, a female Goosander was seen dropping from the bank into the water, followed by four recently hatched ducklings estimated to be no more than two or three days old. They were small enough for two to ride piggy-back as the female swam strongly upstream. The brood was monitored at three to four day intervais throughout June during which time they remained loyal to a stretch of river no more than 800m in length just south of the Norfolk-Suffolk border. By the end of June, ail four young had grown almost to adult size, remaining with the adult bird at ail times. They were not seen subsequently. A very similar sequence of observations was made along the same stretch of river between June 4th and 29th 2007, although on this occasion there were five ducklings which, when first seen, appeared to be seven to ten days old, suggesting that they had hatched perhaps a week earlier than in 2006. The brood survived intact throughout June, again remaining with the female bird at ail times and, as in 2006, were not seen in July. A second breeding pair, also with five young, was recorded a further three kilométrés downstream in Thetford on the Norfolk side of the county boundary.

Goosanders Tony Howe

These observations appear to represent the first breeding records for this species in Suffolk and indeed East Anglia. The stretch of river to which the birds remained loyal is clearly healthy with Kingfisher and Grey Wagtail regularly seen. The water is clear, no more than two métrés deep and free-flowing with short sections of semi-turbulent flow over a shallow gravelly bed. The records seem to suggest at least one wintering pair from the nearby Nunnery Lakes BTO Reserve on the outskirts of Thetford (one of the main strongholds for Goosander in Norfolk with a maximum count of 17 in January 2006) remaining to take advantage of suitable local breeding conditions. Throughout these summer observations the male parent was never seen, neither were the nests located. None of the young birds was lost to prédation, perhaps a little surprising in view of the fact that an Otter was seen on two occasions along the same stretch of river in July 2008.

45


Suffolk Birci Report

2007

References Piotrowski, S. 2003. The Birds of Suffolk. Christopher Helm. Taylor, M., Seago, M â&#x20AC;&#x17E; Allard. P. and Dorling. D. 1999. The Birds of Norfolk. Pica Press. East Sussex. John Law (postscript. In 2008 breeding was once again proven, the female parent this time raising four young. First Seen on June 1 st, they appeared to be at least two weeks old at this time but were only seen intermittently up to June 16th after which time they seemed to disappear. However, all four juveniles were again observed on July 14th by which time they were regularly undertaking short flights low over the river. The female bird was absent whenever the young birds were seen in July. On 25th the fully-fledged offspring were seen leaving the river, flying high to the south before returning to the same Stretch about 15 minutes later. The final observation was on July 28th when two of the brood were again seen flying strongly.]

46

Suffolk Birds 2007 Part 1  

Volume 57

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