Page 1


West Area Recorder Colin Jakes, 7 Maltward Avenue, BURY ST EDMUNDS IP33 3XN Tel: 01284 702215

North-East Area Recorder David Fairhurst, c/o RSPB, Minsmere Reserve, WESTLETON IP17 3BY Tel: 01728 832719 E-mail: davidfairhurst@lycos.com

South-EastArea Recorder Eddie Marsh, 17 Post Mill Gardens, GRUNDISBURGH, IP13 6UP Tel: 01473 735425 E-mail: marshharrier@btinternet.com


SUFFOLK BIRDS VOL. 55 A review of birds in Suffolk in 2005

Editor Malcolm Wright

Assisted by Adam Gretton (Papers) Philip Murphy (Systematic List) Trevor Kerridge (Photos) Tony Howe (Artwork)

Published by SUFFOLK NATURALISTS' SOCIETY in collaboration with SUFFOLK ORNITHOLOGISTS' GROUP

2006


Published by The SufFolk Naturalists' Society, c/o The Museum, High Street, Ipswich IP1 3QH Š The Suffolk Naturalists' Society 2006 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 0264—5793

Printed by Healeys Printers Ltd, Unit 10-11, The Sterling Complex, Farthing Road, Ipswich, Suffolk IP1 5AP.


CONTENTS Page .

Editorial Malcolm Wright

5 7

Review of the Year Malcolm Wright First and Last Dates of Migrants PhiI Croxton and Tim Sparks

.

16

Pomarine Skuas Over-wintering off the North Suffolk Coast 1993-2005 Peter Dure and Paul Reed

. 24

Baltic Gull in Suffolk Brian Small

. 34

Minsmere RSPB Reserve 2005 Adam Rowlands

. 36

The 2005 Suffolk Bird Report: Introduction

. 39

Systematic List

. 41

Appendices

. 152

List of Contributors

. 157

Gazetteer

. 159

Earliest and Latest Dates of Summer Migrants

. 161

A Guide to Recording Birds in Suffolk

. 162

Rare Birds in Suffolk 2005 David Walsh

. 166

Régional Review Adam Gretton

. 170

Suffolk Ringing Report 2005 Peter Lack

. 178

List of Plates Plate

Facing

Plate

Page

No.

No.

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Eider Tim Brown Goldeneye Alan Tate Great Northern Diver Bill Bastón Red-necked Grebe Alan Tate Hen Harrier Bill Bastón Killdeer Robert Wilton Pacific Golden Plover Bill Bastón Red Knot Clive Naunton Little Stint Alan Tate Purple Sandpiper Alan Tate Spotted Redshank Edmund Fellowes

12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.

48 48 48 48 49 49 49 49 96 96 96

Facing Page

Black-tailed Godwit Bill Bastón Lesser Crested Tern Adam Rowlands Whiskered Tern Alan Tate Short-eared Owl Bill Bastón Barn Owl Bill Bastón Nightjar Bill Bastón Kingfisher Clive Naunton Isabelline Wheatear Jim Lawrence Dusky Warbler Brian Egan Long-tailed Tit Bill Bastón Trumpeter Finch Bill Bastón

Front cover: Stone-curlew Peter

Partington

The copyright remains that of the photographers/artist

3

97 97 97 97 144 144 144 145 145 145 145


Suffolk Birci Report 2005

Notice to Contributors Suffolk Birds is an annual publication of records, notes and papers on all aspects of Suffolk ornithology. Except for records and field descriptions submitted through the county recorders, all material should be original. It should not have been published elsewhere or offered complete or in part to any other journal. Authors should carefully study this issue and follow the style of presentation, especially in relation to references and tables. Where relevant, nomenclature and order should follow the latest published for The British List by the British Ornithologist's Union and available on their website at www.bou.org.uk. English names should follow the same list. Contributions should, if possible, be submitted to the editor on disk and written in Microsoft Word. If typed, manuscripts should be double-spaced, with wide margins, on one side of the paper only. They must be in the final form for publication: proofs of longer papers are returned to authors, but alterations must be confined to corrections of printer's errors. The cost of any other alterations may be charged to the author. Photographs and line drawings are required to complement each issue. Suitable photographs of birds, preferably taken in Suffolk, can be either digital or in the form of 35mm transparencies. A payment of ÂŁ12 will be made to the photographer for each photograph published and ÂŁ12 for each drawing. Every possible effort will be made to take care of the original photographs and artwork. However, photographers and artists are reminded that neither the editor nor the SNS can be held responsible in the unlikely event that loss or damage occur. Authors may wish to illustrate their papers, but this will be subject to the illustrations being of the standard required by the editor and the decision on such matters will rest with him or her. Material submitted for publication should be sent to the editor no later than March 1st of each year. Authors of main papers may request up to five free copies of the journal. Any opinions expressed in this Report are those of the contributor and are not necessarily those of the Suffolk Naturalists' Society or the Suffolk Ornithologists' Group.

Suffolk Ornithological Records Committee'. Chair: Richard Drew Area County Recorders'. Colin Jakes, David Fairhurst, Keith Bennett (to 31/12/2005), Eddie Marsh. Secretary. Justin Zantboer Other Committee Members: Will Brame, James Brown, John Grant, Lee Gregory, Peter Ransome, Brian Small, David Walsh, Malcolm Wright.

ADDRESSES Papers, notes, drawings and photographs: The Editor ( S u f f o l k Birds), The Suffolk Naturalists' Society, c/oThe Museum, High Street, Ipswich IP1 3QH. Records: See inside front cover. Suffolk Ornithological Records Committee - correspondence: The Secretary, SORC, c/oThe Museum, High Street, Ipswich IP1 3QH.

4


Suffolk Birci Report 2005

Editorial Later in this Report, the reader will find a paper entitled "First and Last Dates of Migrant Birds in Suffolk 1950-2004" by Phil Croxton and Tini Sparks of the NERC Centre for Ecology and Hydrology at Monks Wood. This paper analyses the arrivai and departure dates of the, mainly summer, visitors to Suffolk over the past fifty-four years, as reported by the county's birders and recorded in past issues of this Report. Their conclusions are quite startling, namely that, on average, spring migrants are now arriving in Suffolk six days earlier than they were at the beginning of the period and the autumn departure is now ten days later, on average, than it was thirty to fifty years ago. So the typical summer visitor is now spending about sixteen days of the year longer in Suffolk than it was just a few decades ago. Other authors have looked at arrivai and departure dates elsewhere in Britain and Europe in recent years and have corne up with similar results. The authors do not go into the reasons behind these changes in their paper, but the evidence is that they are being driven by increasing temperature change, both in Britain and elsewhere. They state "whilst birds cannot anticipate tempĂŠratures in England, these tempĂŠratures reflect general conditions across Europe and the indirect influence of earlier food resources encouraging earlier arrivais". Quite probably this is one more tiny little piece to add to the huge jigsaw which is global warming and climate change. Birds are sensitive indicators of change. Everyone is familiar with the story of the coal miners who took a Canary to the bottom of the pit to check for the presence of carbon monoxide and perhaps this is a modem equivilent. The latest published scientific research into global warming is quite frightening and it begins to look as if it may be proceeding much quicker than scientists thought even five years ago. Recent research by American and Russian scientists has found that the Arctic permafrost, which is starting to melt due to global warming, is releasing five times more methane gas than they had previously predicted. They also calculate that methane has a global warming potential which is 23 times worse than the same amount of carbon dioxide and there may be as much as 450 billion tons of methane and carbon dioxide trapped in the world's permafrost. The danger is of a runaway affect; the more permafrost is melted, the warmer it becomes and even more permafrost melts, leading to a vicious, accelerating cycle of temperature rise and climate change. Separate research by American scientists from NASA has shown a great surge in the disappearance of Arctic ice cover in the past two years, with an area almost the size of Turkey gone in a single year. The engine driving these changes is, of course, man's burning of fossil fuels and misuse of the planet's resources. So what does the future hold for Suffolk's birds, if these trends continue? This is impossible to predict, but the overall effects are very unlikely to be beneficiai. If the polar ice-caps and ice-sheets eventually melt, it will increase sea-levels by many metres and most of our finest nature reserves, such as Minsmere, Walberswick and Trimley Marshes, will go under the sea. Already there are big gaps in the sea wall along the Walberswick shore, which are not being repaired. Habitats will change radically; the Sandlings and Breckland, being on very light, sandy soils, could lose ali their heather and perhaps trees as well and end up as semi-desert, for instance. Some species will inevitably retreat to the north (or become extinct) and it appears that this process has already begun within Britain, with a rapid decline in the population of Ring Ouzels on the high moorlands, which is believed to be due to climate change. The consĂŠquences for people are likely to be equally serious and unpredictable. Much valuable land around the coast may be lost to the sea and it no longer seems like a good idea to buy a holiday cottage anywhere near sea level. Agriculture in the county is likely 5


Suffolk Birci Report 2005 to be turned upside down - perhaps devastated if summer droughts intensify in what is already a low rainfall area. Some scientists predict that if the Greenland ice-cap melts, it would "switch o f f " the warming Gulf Stream current, leading to far more severe winters in Britain. So we could get squeezed from both sides and end up with an extreme climate with very hot summers and very cold winters. While some politicians in this country have been making the right noises about global warming, so far there has been a real lack of initiatives and the really serious action needed to start to combat it. Further afield, the situation could make sane men and women despair, with China building new coal-fired power stations at the rate of one per week, while the current American administration is a disaster for the whole world; tied to the oil lobby and with its head in the sand, denying that a problem even exists. We all deserve much better from our "leaders". In the meantime, every one of us should do what we can to reduce our impact on this sensitive earth: make sure that your house is as well insulated as it can be, install low energy light bulbs, recycle whenever possible, buy a more economical car next time you change it and so forth. Bird your local patch more often, rather than travelling a distance and, if you can, then walk or cycle when you go out into the countryside. Chasing around the county to set a new record year total is most definitely a non-starter. My thanks are owed to many people who have contributed to this Report. Firstly to the many observers, reserve wardens and volunteers, WeBS counters, BBS surveyors, the observers at Landguard and Orfordness and bird ringers who have sent in their records from which the Report is written. The three county recorders, Colin Jakes, David Fairhurst and Keith Bennett enter all the records onto the computer system and are a vital part of the process and our thanks are due to them for much hard work. Keith has retired now as recorder for the south-east and has been replaced by Eddie Marsh. Sixteen different authors have written the systematic list and they are credited at the beginning of that section, while the papers have been contributed by Phil Croxton and Tim Sparks, Peter Dare and Paul Read, Brian Small, Adam Rowlands, David Walsh, Adam Gretton and Peter Lack. My thanks to them all. Philip Murphy has once again read through all the systematic list and made many corrections and suggestions for improvement, for which I am most grateful. Adam Gretton has edited the papers and given much valuable support, while Richard Drew and Philip Murphy have read and commented on the Review of the Year. Trevor Kerridge and Tony Howe collated the photographs and artwork respectively and Peter Partington painted the splendid cover illustration of a Stone-curlew. Our thanks to the artists and photographers, for allowing us to use their work. Peter Lack has helped me to sort out various IT problems again, David Walsh dealt with all the BBRC records and Justin Zantboer helped in numerous ways as secretary of SORC. Andrew Gregory has assisted with publicity and distribution of the Report. The monthly weather summaries in Review of the Year were compiled with assistance from Ken Blowers articles in the EADT and also data from the Met Office website. My thanks especially to my family, who have helped in numerous ways and particularly to Rosemary, who has read the whole Report to look for errors. Mike Gaydon, at Healeys, has seen it all into print with his usual efficiency. Malcolm Wright Pakenham 6


Suffolk Birci Report 2005

Review of the Year Malcolm Wright Weather The year began with a mild and dry January, but February was much colder with persistent winds from a northerly point and nearly 75mm (three inches) of snow fell on 23rd. March also began cold with snow showers; it was very warm mid-month for a few days but then became colder again. April was a notably warm month, with daytime maximum temperatures exceeding the average on 26 days. The seesaw continued in May, with a cold spell of 11 days in mid-month, which brought northerly winds and night frosts and probably damaged the breeding season for some species. June was the driest for 43 years, but the rest of the summer was unsettled with only short spells of hot and sunny conditions and a deficit of sunshine. In contrast the autumn was exceptionally warm and ranked as one of the most favourable in the past 100 years, with temperatures well above average. Early November was mild, but then freezing cold northerly winds set in and gave an early taste of winter with some snow. December was milder and very dry until 27th, when bitter cold winds brought more snow. Overall it was a dry year and rainfall in Ipswich was about 75mm (three inches) below the long-term average. Much of the deficit came in the winter months and resulted in low ground-water levels and parched wetlands. Rarities There were two additions to the Suffolk list in 2005; a Killdeer in fields on the south side of Breydon Water in late March and a Pacific Golden Plover at Levington Creek on the River Orwell in August. The over-wintering Dusky Warbler from 2004 stayed at Kessingland until mid-April and the Glossy Ibis at Burgh Castle remained until early March. Highlights of the spring included two Alpine Swifts, a Whiskered Tern at Lakenheath Fen, a pair of Black-winged Stilts on Orfordness, a party of seven Bee-eaters at Dunwich and the splendid Trumpeter Finch at Landguard Point. The summer was more productive than in some recent years and saw records of Caspian and Gull-billed Terns, a Red-footed Falcon at Walberswick, a long-staying Marsh Sandpiper at Minsmere and North Warren and a Lesser Crested Tern at both Minsmere and East Lane, Bawdsey. The warm autumn which followed was rather ordinary, but October still featured a Red-rumped Swallow at Covehithe, an Isabelline Wheatear at Landguard, an Olive-backed Pipit at Thorpeness, and a Dusky Warbler at Southwold but only two Pallas's Warblers. At the end of December there was an Arctic Redpoll near Icklingham. Breeding Birds The numbers of Little Egrets continue to climb. The January WeBS counts reported a total of 73 wintering birds on the four main southern estuaries, about 30 pairs nested in 4 colonies and a new Suffolk record count was set in October, when 112 went to roost at Loompit Lake on two dates. Bittern numbers are increasing much more slowly, but 20 booming males were present in 2005, which is one more than the previous year and represents 43% of the British population. About 125 young Marsh Harriers were fledged, from the 46 nests that were located and Buzzards continued to consolidate their recent re-colonisation of the county. Hobbys are also doing well and the county population is now considered to be at least 40-50 pairs. 7


Suffolk Birci Report 2005 At Minsmere, 104 pairs of Avocets nested and succeeded in fledging 36 young, but the 67 pairs on Havergate Island and the 30 pairs on Orfordness lost all their young to predators. The number of Stone Curlews breeding in Suffolk is static at present (at least 85 pairs bred) but the population as a whole is slowly edging up and reached 300 pairs nationally in 2005. Little Ringed Plovers are more precariously placed, with under ten pairs nesting in Suffolk. Mediterranean Gulls nested for the first time at Minsmere, with four pairs breeding on the Scrape, but only fledging two chicks and there were up to ten pairs at a more established site. Little Terns had a poor year, with at least 73 pairs at eight colonies fledging no more than about 12 pulii. There were 146 singing male Wood Larks in the Sandlings and 135 singing males in the Suffolk part of Thetford Forest, plus an unknown number of pairs on heathland and farmland in the latter area. Although these figures are well down on the peak years of 1999/2000, the county still holds a substantial proportion of Britain's Wood Larks. A total of 79 singing male Cetti's Warblers was reported from 30 sites and Dartford Warblers moved into three figures, with 113 pairs found at ten sites. Bearded Tits maintained their high numbers in the reedbeds on the coast and the population at Lakenheath Fen (three pairs in 2004) shot up to 14 pairs. Two pairs of Golden Oriole nested successfully at this latter site and there were indications of a small recovery in Tree Sparrow numbers. It was not such a good breeding season for many of our commoner birds in 2005. At Lackford Lakes, the number of adults trapped on the Constant Eifort Site (CES) ringing scheme was 130 (128 in 2004) but the number of juveniles trapped was well down at 208 (318 in 2004). Wetland species, such as Snipe and Redshank, continue to decline and there is little sign so far of a recovery in numbers for many farmland birds, such as Lapwing, Skylark or Corn Bunting, although new agricultural grant schemes give optimism for the future. Concern must also be expressed for the populations of some of our summer visitors wintering in Africa, such as Redstart and Willow Warbler, which are declining quickly and are evidently being affected by currently-unknown factors on migration or in their winter quarters. January The month was very mild overall and quite sunny, but with well below normal rainfall. The first two weeks were unsettled and deep Atlantic depressions produced some strong winds. A gale on 7th was accompanied by gusts of over lOOkph (60 mph) which felled a 25 metre (80 feet) high beech tree in Ipswich cemetery. Also on 7th, temperatures were as high as 14C (57F), a figure more typical of April. The second half of the month saw an anticyclone dominate and it became more settled, dry and cloudy with northerly breezes. Some snow fell on 24th but melted rapidly. It was the third successive month with a large rainfall deficit, with most places recording only about 25mm (one inch) of rain. No doubt all of Suffolk's keen birders were out early on the 1st and among the finds that day were a female Ferruginous Duck on Alton Water, an early singing Wood Lark on Sizewell Common, a flock of 80 Waxwings in Ipswich, the long-staying Great Grey Shrike on Weather Heath, Elveden and at Kessingland, 140 Snow Buntings and the over-wintering Dusky Warbler. The latter, found on December 2nd 2004, was to stay until April 18th. A flock of 60 Twite was on the shore pools at Dunwich on 4th and four Slavonian Grebes inhabited Alton Water between 6th and 18th. The monthly winter WeBS count found no less than 616 Pintail on the Blyth Estuary, while on the four southern estuaries (Aide/Ore, Deben, Orwell and Stour), the observers counted a total of 73 Little Egrets. A day-total of 1393 Red-throated Divers was reported offThorpeness on 13th and this 8


Review of the Year is the highest count of the year. Two sub-adult Caspian Gulls frequented the Blyth Estuary on 15th and a third, an adult, was seen at North Warren on 23rd. On 16th, there were 14 Water Pipits at Minsmere and a flock of 120 Snow Buntings on Orfordness. There was a very low total of just eight Hen Harriers in the coastal roosts, but there were several sightings of Rough-legged Buzzards, including two on the Deben Estuary between 23rd and 30th.

Smew Peter Beeson

At least four Merlins wintered along the coast and eight or nine Peregrines. The numbers of Pink-footed Geese seen in the county are increasing year by year; as more birds winter in Norfolk, some push further south and the 5000 at Burgh Castle on 22nd sets a new mark. The rarity of the month was without doubt the Black Guillemot, which flew north close inshore off Sizewell on 24th; there were only four confirmed records of this species in Suffolk during the whole of the last century. The four Hawfinches recorded at Sotterley Park on 27th proved to be the highest count of the year for this charismatic finch, while the 115 Bewick's Swans which flew over Minsmere on 31st must have made a fine spectacle. February The first twelve days were similar to late January, with a blocking anticyclone dominant and rather quiet, mild and dry conditions. Strong sunshine on 12th took temperatures up to 13C (55F), but then winter arrived with a vengeance on 13th, when a very cold, persistent, northerly airstream set in, which was to last until the month s end. During this spell, there were showers of hail, sleet and snow and then a heavier snowfall on 23rd, when nearly 75mm (three inches) was measured in Ipswich. More snow and hail showers gave another covering early on 27th. Rainfall in Ipswich was a little above the long-term average. Three Black Redstarts seen at the Sizewell power stations on 6th were presumably over-wintering there. Up to three Smew were reported at Minsmere throughout the month and there was also a redhead on Alton Water. A drake Green-winged Teal on Lakenheath Washes from 12th to 16th was seen on the Suffolk side of the county boundary on 12th and 13th at least. That scarce auk, the Puffin, was seen offshore at Felixstowe on 14th and Southwold on 22nd and 24th, while the scarce gulls were represented by a second-winter Iceland Gull at Minsmere/Sizewell from 19th until March 13th and a first-winter Glaucous Gull in Lowestoft harbour on 21st. The long-staying Glossy Ibis was seen occasionally at Burgh Castle throughout the month. Among high WeBS counts reported in February were 730 Avocets and 4819 Lapwings on the Aide/Ore Estuary; 1408 Curlews on the Stour; a total of 4348 Redshanks on the four southern estuaries and 575 Turnstones on the Orwell and Stour. March The northerly winds and consequent wintiy weather persisted well into March, with some heavy snow showers in the first few davs. Over the period 2nd to 4th, a total of 100mm (four inches) of snow was measured in Ipswich and overall it was the coldest early-March weather since 1987. From 10th onwards there was a slow rise in temperature and then a warm southerly airstream took the mercury to 19C (67F) on 16th, well above the seasonal 9


Suffolk Birci Report 2005 normal and brought with it the first Wheatears, Sand Martins and Swallows. Temperatures feti back on 20th and several following days saw heavy cloud and gloom. The month ended dull and cool, with spells ofrain and drizzle. Yet again, there was a deficit of rain. Apart from a roost count of 140 Corn Buntings at Lakenheath Fen on lst, there was little of note during the first ten days but then signs of spring arrived on 11 th, with a drake Garganey on the Scrape at Minsmere. A Hooded Crow was on Orfordness on 13th/14th and then the much warmer weather on 16th brought in the first Wheatear and Sand Martin, followed by a Swallow on 17th and five Stone Curlews in Breckland on 19th. There was a count of 470 Great Crested Grebes on the sea offDunwich on 17th and high WeBS counts included a total of 7274 Wigeon on the Aide/Ore Estuary and 5506 Dunlin on the Suffolk shore of the Stour. A Black Brant was seen intermittently at Shotley/ Erwarton Marshes between lOth and 3lst. The warm speli in mid-month also produced a very good run of Black Redstarts, peaking with 15 at Landguard on 2 lst. Even better were the three male Bluethroats, of the white-spotted form, at the same site between 20th and 23rd. Also at Landguard on 23rd, a Black-necked Grebe swam south on the sea, on 24th a Rough-legged Buzzard flew over Benacre and on 26th, three Shore Larks were on Orfordness. The bird of the month was found late; the first Suffolk Killdeer was discovered in a field near the south wall of Breydon Water on 28th. It showed only briefly to the finder on that day, but was admired by many on 29th. Aprii A quiet month, weather-wise, with temperatures above average on 26 days, but once more a rainfall deficit, in spite of some traditional Aprii showers. There was a short colĂ speli around 8/9th, when a stiff northerly wind kept temperatures below 7C (45F). Snow fell on 9th but soon melted. An anticyclone became established about I lth, but generally low pressure dominated and winds were mainly light and varied, between south-west and south-east. There were more than 12 hours of sunshine on 21st and temperatures reached 20C (68F) on 30th, as warm air pushed up from the south. The first Nightingale was singing at Minsmere on 4th and what is presumed to have been the same Alpine Swift was seen at Minsmere, Sizewell and Thorpeness on 5th, 6th and 7th. Another Caspian Gull was at Minsmere on 8th. Early Hobbys were noted at Orfordness and Holton St Mary on 9th and the first Whitethroat was at Minsmere on this date. A Turtle Dove at Bramford on 11 th was quickly followed by the first Cuckoo the following day, when a Raven was seen at Holbrook Park. A Wryneck at Landguard on 20th was the only one of the spring. Further arrivals of summer visitors included the first Garden Warbler at Hardwick Heath on 22nd, the first Swift over Landguard on 23rd and a Whinchat at Boyton Marsh on 26th. A Wood Warbler at North Warren, also on 26th, was the first of six found within a week. A distinctly quiet month ended with two Cranes seen at Minsmere on 28th. May The first few days were very warm but unsettled, with some thundery rain. It then became cooler with showers and from lOth a ridge of high pressure became established, giving more settled, dry conditions, but quite cold with some night frosts. A chilly easterly wind gave a noticeably cold day on 13th and it remained very cool far the next few days. Low pressure returned front about I9th, bringing south-westerly winds, some rain and warmth. By 27th the wind was in the south and it was hot, with the mercury reaching 27C (81F). A cold front brought fresher conditions on 28th and the 30th was quite wet. 10


Review of the Year A Grey-headed Wagtail was at Landguard on 1st and 2nd and on the latter date an adult Whiskered Tern was watched by many along the Little Ouse River at Lakenheath Fen. Also on 2nd, a Great White Egret was at North Warren and it was subsequently seen at Minsmere on 4th, 5th and 17th. North Hoopoe Peter Beeson

Warren also attracted a Purple

Heron, a sub-adult present in the reedbeds from 5th to 15th and two Cranes were at this site on 13th. The solitary Temminck's Stint of the year was present at Lackford Lakes on 4th and 5th and there were two Hoopoes, the first present around Icklingham between 5th and 11th and another at Westleton on 9th. A Montagu's Harrier flew north over Westleton Heath on 8th. After a slight lull, a party of seven Bee-eaters over Dunwich on 14th provided an exciting antidote. There was an excellent passage of Pomarine Skuas in mid-May, peaking between 12th and 15th at Kessingland, Covehithe, Thorpeness and Landguard. The 16th saw a pair of Black-winged Stilts on Orfordness, a Red-backed Shrike at Minsmere and a Golden Oriole at Landguard and there was another Golden Oriole at Minsmere on 17th. Several Quail were also singing at this time, including two at Gisleham from 14th and two at Westleton from 15th. The 21st saw the discovery of Suffolk's 2nd and Britain's 9th Trumpeter Finch at Landguard Point. Many hundreds of observers came to enjoy it during its six day stay. The 21st also produced a Honey Buzzard soaring over Flatford Mill, with further birds at Minsmere on 25th and King's Fleet on 26th. A Montagu's Harrier was also at King's Fleet, on 23rd. A female Serin was at Landguard on 26th and on 30th a Raven flew over Hanchett, near Haverhill. June A remarkably dry month, with just 9mm (0.35 inches) of rain measured in Ipswich, making it the driest June for 43 years. It was unsettled for the first few days, but from 6th onwards a high pressure system intensified over the British Isles. From mid-month the temperatures rose as very warm air pushed up from the south and this peaked on 23/24th with the mercury at 29C (84F) and high humidity. With conditions still very hot, a spectacular hailstorm affected parts of south Suffolk on 29th. A Honey Buzzard flew south over Livermere Lake on 3rd and was seen just three hours later at Great Barton, three kilometres to the south; another Honey Buzzard was watched over High Lodge, Brandon, on 6th. Minsmere recorded its second Red-backed Shrike of the spring on 4th and on 8th a Tawny Pipit was found in the dunes there and a Golden Oriole was singing near Benacre. A Marsh Warbler was at Hollesley Bay between 5th and 11th and a second bird took up residence near Frostenden on 7th and was heard singing there until at least 18th. The 14th produced three contrasting rarities in the shape of a male Red-footed Falcon at Westwood Marshes, a Gull-billed Tern, which flew north off Landguard and a second Alpine Swift between Dunwich and Walberswick. Two adult Roseate Terns were at Minsmere on 18th. A Long-tailed Duck at Loompit Lake on 19th was most unseasonable, 11


Suffolk Birci Report 2005 but was outshone by a Caspian Tern seen along the south shore of Breydon Water and the 20th saw a Bee-eater flying over Landguard. A Night Heron was seen rather briefly at Minsmere on 24th and several Quail were calling at various sites around the county. July The first week was unsettled, with rain on 4th, but from 7th an anticyclone became established, giving mainly dry, sunny and warm conditions for the next two weeks, but with some scattered thunderstorms at times. A depression crossed southern England on 24th and the last week was very unsettled, with rain and strong winds. On 27th London recorded its coldest July day for 25 years, with the temperature only reaching about 15C (59F). A Kentish Plover frequented Breydon Water in early July and was seen on the south side of the estuary at least on 2nd and 10th. There was a good sequence of Roseate Terns, with an adult at Minsmere on 8th and 9th, a first-summer there on 12th and then an adult at Trimley Marshes on 15th. Minsmere then produced a great run of good records, with a Bee-eater on 14th, a Great White Egret from 15th to 17th, a Marsh Sandpiper from 16th to 20th, a Lesser Crested Tern on 20th and 21st and two Long-tailed Skuas and seven Arctic Skuas soaring together over the sluice on 22nd. The Marsh Sandpiper re-located to North Warren from 21st to 25th and the Lesser Crested Tern was refound on the shore at East Lane, Bawdsey, on 22nd. Away from Minsmere, a White-rumped Sandpiper was watched on the south shore of Breydon Water between 18th and 20th and a Marsh Warbler was trapped at Hollesley Bay on 26th. Two Caspian Gulls returned to the Southwold area; a second-winter on 28th and a Kiev-ringed third-winter on 30th and the latter bird was seen along the coast into November. Finally, an adult White-winged Black Tern at Minsmere/Sizewell on 29th completed an interesting July. August August was a disappointing, cloudy, unsettled month with below-average sunshine. North-westerly winds were often a feature of the weather and they resulted in cool conditions on a number of days. Rain fell on twelve days and in Ipswich was measured at 65mm (2.56 inches), a little above the long-term average. The coolest day was the 9th; the 19th and 24th were both very wet and there was a brief heat wave late in the month, when temperatures approached 26C (80F). Lowestoft shared in the records of Roseate Tern with an adult found there on 3rd. Inland, a count of 23 Turtle Doves on wires in Long Melford on 6th was the best of the year. The 7th saw a Cory's Shearwater off Slaughden and another Caspian Gull was found at Southwold. On 10th a Goshawk flew over Westleton Common and another Roseate Tern was offshore at Aldringham on 12th. Spoonbills cross the North Sea from Holland to Suffolk in late summer every year and the peak count this August was 22 at Havergate Island on 16th. A Red-backed Shrike was at Kessingland on 19th and 20th and 26 Sooty Shearwaters were logged north off Thorpeness on 21st. Only a solitary observer was fortunate enough to see the Buff-breasted Sandpiper on Orfordness on 23rd. On 25th, 30 Black Terns were feeding round the Sizewell rigs and Curlew Sandpipers peaked at 39 on Orfordness on 26th. The bird of the month was easily Suffolk's first Pacific Golden Plover, found on saltings beside the R.Orwell at Levington Creek on 26th and present there until 31st. Sometimes it flew across the river to saltings on the south bank and so could be elusive, but it was eventually seen by most observers. Two Pectoral Sandpipers briefly visited the Scrape at Minsmere on 27th. 12


Review of the Year September It was one of the warmest Septembers in the past half century and RAF Wattisham recorded an average maximum temperature of20C (68F). The month began with high pressure to the east of Britain and very warm, humid conditions affected all areas. Over 9/10th, a 24 howrainfall of 41mm (1.61 inches) was recorded in Ipswich and more heavy rain fell on 15th. For the last ten days of the month winds were from a south-westerly direction and there were long spells of sunshine. In most places rainfall was above the long-term average. On 2nd a Pectoral Sandpiper was found at Trimley Marshes, which stayed until 9th and a Honey Buzzard flew over the Trimley/ Levington area. A Marsh Warbler at Landguard on 4th was identified in the field and the identification was later confirmed in the hand, to the relief of those involved. The same day an adult and a juvenile Purple Heron flew over Aldringham. A Redbacked Shrike, found at North Warren on 5th, stayed until the 9th and on 6th a Grey Phalarope flew south at Southwold. It was an excellent month for Wrynecks and 12 were found between 7th and 26th, involving ten on the coast and two inland at Flixton and Bucklesham.

A juvenile

Rose-coloured Starling Su Gough

Rose-coloured

Starling was at Landguard from 7th to 12th. Another Pectoral Sandpiper visited Minsmere on 11th and on 12th there was a Barred Warbler at Landguard and a Wood Warbler at Benacre Broad, both the sole records of the autumn. A Leach's Petrel flew north up the coast past Southwold and Kessingland on 16th and on 17th two more Caspian Gulls were observed in the Southwold/Benacre area. Also on 17th a solitary Dotterel was seen on Lavenham Airfield, the only record of the year of this sought-after wader. Yellow-browed Warblers were found at Gunton on 17th and Thorpeness on 22nd, the vanguard of the October invasion and a late Honey Buzzard was seen over Leiston on 24th. October A long spell of persistent southerly winds led to another warm month and the long term daytime average temperature of 14C (57F) was reached or exceeded on 29 days. The warmth was due to an airflow originating in northern A frica, as evidenced by the traces of Saharan dust deposited on parked cars in some parts of the region. Somewhat surprisingly, there was little evidence of rarities from the south and most of those which occurred were of an easterly origin. There was little rain for the first 20 days, but a deep depression passing close to the north of Britain gave gales and rain on 24th and 25th and by the end of the month total rainfall was at or above the long-term average in most places. The temperature in Ipswich reached 20C (68F) on 30th. A Red-rumped Swallow flew south over the clifftops at Covehithe early on 1st and a Red-backed Shrike, found close-by at Benacre, was to stay until the 3rd. The find of the month was Suffolk's third Isabelline Wheatear at Landguard on 4th, but its stay was brief. The 112 Little Egrets counted into the roost at Loompit Lake on 5th was a new county record and that total was reached again at the same site on 16th. A Lesser Yellowlegs was on the Scrape at Minsmere between 9th and 11th. 13


Suffolk Birci Report 2005 It was certainly a Yellow-browed Warbler month and almost 40 were recorded, with at least 15 in the Lowestoft area alone and two inland, at Long Melford on 2nd and Brettenham on 7th. By comparison, there were just two Pallas's Warblers, at Thorpeness on 14th and Southwold on 18th and in-between these was the sole Dusky Warbler, at Southwold on 16th. An Olive-backed Pipit was also found on 16th, at Thorpeness and it stayed until 20th and a Red-breasted Flycatcher was at Landguard on 16th and 17th. Three Lapland Buntings were on the clifftops at Corton on 14th and three more were on Orfordness on 16th and a Bluethroat was seen at Landguard on 17th. The wintering Great Grey Shrike had returned to Weather Heath, Elveden on 9th and further birds, evidently passing through Suffolk, were at Lackford Lakes on 15th, Kessingland on 17th and Corton on 23rd and 24th. Out at sea, Balearic Shearwaters were recorded off Kessingland and Southwold on 14th and Slaughden on 20th. Late in the month a Richard's Pipit was on Orfordness on 27th and a Crane flew over Aldeburgh on 28th. November It was a month of two very contrasting halves. The first 13 days were mild with southwesterly winds from the Atlantic and temperatures exceeded 9C (48F) on every day. On 2nd and 3rd the mercury reached I7C (62F). The change came on 14th, as a cold north-westerly airstream extended across Britain, introducing a spell of wintry weather which lasted until the month's end. There were snow showers during this cold spell, with some places reporting more than an inch of snow and the coldest day was 25th, when freezing winds gave an arctic feel to the day. Yet again rainfall was below the long-term average. Seawatching off Southwold on 3rd produced a Storm Petrel and a juvenile Sabine's Gull and also on 3rd, a solitary Shore Lark arrived at Minsmere to spend the winter there. A total of 16 Red-necked Grebes was seen offshore during the month and four of these flew south at Covehithe on 4th and another four flew south there on 27th. A Hooded Crow was on Sudbourne Marshes on 5th. Inland, eight Stone Curlews were still on a Breckland site on 13th, but these were the final birds of the year. Grey Phalaropes were seen offshore on four dates between 6th and 25th but only small numbers of Little Auks were encountered, with a month's total of 14 north at Covehithe being the highest from any location. There was a strong showing from Marsh Harrier Peter Beeson Slavonian Grebes, with a peak count of seven on the River Orwell at Fox's Marina on 20th and the accumulated WeBS total of wintering Black-tailed Godwits at the eight main sites was 2010. A Ring-billed Gull was seen at Covehithe Broad on 17th but did not stay and a Long-eared Owl was at Landguard on 19th, with a second bird in off the sea on the same date. December December was another dry month, with some localities reporting rainfall of more than 25mm (one inch) below the average. Low pressure held sway during the first week, but 14


Review of the Year thereafter high pressure systems were largely dominant. Fog was widespread on 11th and cold air from the Arctic reached the region on 16th, with gusts ofSOkph (30 mph). The run up to Christmas saw south-westerly winds and mild conditions, but on 27th bitterly cold east winds originating in Siberia swept into East Anglia. Up to 63mm (2.5 inches) of snow fell in Ipswich and on 29th the maximum temperature failed to exceed —2C (28F). Thus the year ended on a very cold note. Crossbill numbers increased during the year and among the flocks in The King's Forest were 40 at North Stow on 3rd and 36 at West Stow on 5th. On 10th eight flocks of Bewick's Swans, with about 50 birds in each flock, were reported flying over Ingham, near Bury St Edmunds. They must have been a fine sight and were, no doubt, heading for their wintering grounds on the Ouse Washes. On 15th a Black Brant was located on the Orwell Estuary and it was to stay well into 2006. Up to 307 White-fronted Geese were at North Warren during the month and up to 750 Barnacle Geese could be found near Southwold, although the origins of the latter are unclear. The December WeBS count of Teal on the Aide/Ore Estuary was 3126, the highest total of the year. The year ended with an excellent inland find; amongst a flock of 25 Mealy Redpoll found near Icklingham on 31st was an Arctic Redpoll and it stayed well into the New Year.

Barn Owl Peter Beeson

15


Suffolk Birci Report 2005

First and Last Dates of Migrant Birds in Suffolk 1950-2004 Phil Croxton and Tim Sparks NERC Centre for Ecology and Hydrology, Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire PE28 2LS This paper examines the first and last observations of migrant birds in Suffolk, as reported by Suffolk Birds and its preceding publications, since 1950. Some earlier records exist, for example, for seven years between 1932 and 1947, but these tend to be patchy and incomplete. The Suffolk record is especially important for its continuity and for the inclusion of autumn departure dates which are always, quite understandably, more difïïcult to obtain than spring records. We looked at the recorded dates of 46 migrant bird species (Table 1 ), consisting of 44 summer visitors and two winter visitors, Fieldfare and Redwing. Our aim was to summarise first arrivai and last departure dates and examine the data for shifts in dates over time. We decided to omit Savi's Warbler from this paper as it had only eight records for first sighting and just one last sighting record. The increased overwintering patterns of Blackcap and Chiffchaff resulted in a virtual end to first and last records for these species in 1985. P.W. Murphy (1981), in a review of Suffolk migration dates, remarked on the increase in overwintering birds and the trend towards later observations reported in the autumn. Overwintering has been reported in Suffolk Birds for further species including Whimbrel, Greenshank, Common Sandpiper, Turtle Dove, Swallow, Yellow Wagtail, Black Redstart, Ring Ouzel and Willow Warbler. For purposes of analysis, ail dates were converted to days post December 31. So, for example, the 14th February becomes day 45 and the 8th Aprii day 98. Dates in Leap Years are modified accordingly. The data were examined by dividing the sériés into two approximately equal parts, 1950-1977 and 1978-2004. Différences in mean first and last dates between these two periods were calculated where at least ten years of data were recorded in each half, and compared using two sample t-tests. Results A summary of first observations is given in Table 1. The standard déviation varies greatly for these species, reflecting consistency in arrivai dates. For 31 species there were at least ten years of data in the two "halves" and these have been examined for change. Of the 29 spring arrivais, 27 were earlier in the more recent period (of which 19 were significantly earlier). Both species getting later, i.e. Redstart and Red-Backed Shrike, were significantly later. The average change in the 29 spring species was 6.2 days earlier. There was no significant change in the two autumn arrivais (Fieldfare and Redwing). When changes to Hobby were ignored (a very strong trend to earlier arrivai) there was a corrélation between change in dates and mean arrivai date (r=0.42, p=0.027, Figure 1), suggesting that it was the earlier-arriving species that were becoming more early. An example of first arrivai date of a species with a change in arrivai date close to the average, Sedge Warbler, is given in Figure 2. A summary of last observations is given in Table 2. As for first observations, the standard déviation in dates varies greatly between species. Ten years of data were available in both "halves" for 31 species, although these were not exactly the same species as for arrivai. Of the 29 autumn departures, 26 were later in the more recent period and 14


First and Last Dates of Migrant Birds in Suffolk

1950-2004

significantly so. Of the three species to leave earlier in the recent period, one (Nightjar) was significantly earlier. The average change between the two periods for the 29 autumn departures was 10.0 days later. There was no significant change in the dates of the two spring departures. Unlike arrivais, there was no significant corrélation between change and mean departure date (r =-0.07, p=0.72. Figure 3). An example of last departure date of a species with a change in departure date close to the average, Spotted Flycatcher, is given in Figure 4. Overall there was a strong relationship between mean first arrivai date and mean last departure date (r = -0.51, p<0.001. Figure 5), with early arriving species tending to be those which departed latest, and vice-versa. There was, however, no overall pattern between change in first arrivai date and change in last departure date (r = -0.13, p = 0.53, Figure 6), other than a general tendency for earlier arrivai and later departure. It is not altogether clear what is driving these changes in arrivai and departure date. We must not overlook the possibility that earlier arrivais and later departures may be partly caused by recording biases from increased observer effort or of growing (bird) population size. However, since the majority of species are probably in decline, this would result in a tendency to observe arrivais later and departures earlier; for example, masking trends in the rapidly declining Cuckoo. The focus of this paper is to report changes in migration dates and there isn't sufficient space to analyse the causes of the changes. A quick-and-dirty analysis of dates with Central England monthly temperatures would suggest that 16 of the species show a significant negative corrélation between arrivai date and temperature (warmer = earlier) and eight of the species show significant positive corrélation between departure date and temperature (warmer = later). Whilst birds cannot anticipate temperatures in England, these temperatures reflect general conditions across Europe and the indirect influence of earlier food resources encouraging earlier arrivais. We hope to undertake a more complete analysis of arrivai and departure dates in Suffolk, in relation to temperatures both in Britain and further south, at a later date. Discussion Lehikoinen et al. (2004) reported that almost 40% of 1000 European series of spring arrivai dates were significantly earlier and only 2% significantly later. The Suffolk arrivai data summarised here, which were not included in the Lehikoinen et al. summary, show 60% of species were significantly earlier. There are fewer studies of autumn departure, but the results summarised here suggest almost 50% of species were departing significantly later. The length of the Suffolk record clearly helps in detecting changes over the last half century. Combining the mean changes in spring (-6.2 days) with those in autumn (10.0 days) suggests that summer visitors spent 16 days longer in Suffolk in the second half of the study period compared with the first half. A number of studies of county bird report data have already been published. Much of the data summarised in our paper concurs with these. However, county bird report data need to be treated with some caution hearing in mind the growing observer effort over the years. The dates of rarer, or more-difficult-to-observe, species are most likely to be influenced by changing recorder effort. This may also be true of species undergoing dramatic increases (likely to result in earlier spring and later autumn observations) or decreases (effect opposite to above). Hobby, for example, may fall into more than one of the above catégories. Dates for the more common, highly-visible species, such as Sand Martin, provide us with more reliable information. In fact, the earlier arrivai of Sand Martin in this analysis by 13 days, confirms changes seen in Sussex, Essex, Avon, 17


Suffolk Birci Report 2005 Leicestershire, Sheffield and Wharfedale. We have not yet found a eounty report that does not show a marked advance in Sand Martin arrivai. An obvious comparison should be with the analysis of data from the Essex Bird Reports covering the years 1950-1998 (Sparks & Mason, 2001). The Essex analysis (admittedly based on another method) did not include the most recent six, globally-warm, years included in our Suffolk analysis. It is not surprising, therefore, that whilst ten of 32 examined Essex species were significantly earlier, the ĂŠquivalent figure, as we have seen, was 19 out of 29 in Suffolk. Similarly autumn departures in eight out of 32 species were significantly later in Essex, coinpared with 14 out of 29 in Suffolk. Overall the order of species' mean dates in spring between the two counties agree (r = 0.96, p<0.001), although Suffolk was some three days later on average (paired t = 3.98, p<0.001). Order of autumn departures also agreed (r = 0.91, pO.OOl) and departure was, not significantly, one day later on average in Suffolk (paired t = 0.85, p = 0.40). There was no agreement between the two counties in variability of dates (species standard dĂŠviation) in either spring (r = 0.11, p = 0.51) or autumn (r = 0.07, p = 0.67). Of the ten species significantly earlier in spring in Essex, seven (Wheatear, Sand Martin, Whimbrel, Tree Pipit, Reed Warbler, Hobby and Swift) were also examined in this paper and ail were also significantly earlier. Of the eight significantly-later autumn species in Essex, seven were also analysed for change in this paper and five (Tree Pipit, Lesser Whitethroat, Garden Warbler, Whinchat and Reed Warbler) were also significantly later. Despite some misgivings about what these changes actually mean for the entire migrant populations, there can be little doubt that species are responding to temperature increases operating over the continental, or larger, scale. The Suffolk data benefits from having the recent warmer years in its analysis and thus produces a greater number of significant changes in dates than did the analysis of the Essex data, based on years to 1998 only. Murphy (1982) drew on other data sources to report first and last dates of birds in Suffolk between 1950 and 1980 and drew attention to more extreme dates taken from older literature. We deliberately chose, for continuity, to confine our analysis to data contained in summaries in Suffolk Birds and its preceding publications. Acknowledgements We thank the many hundreds of individuĂĄis who have contributed to the data summarised here and which, through their tenacity, has now proven to be so valuable. References Lehikoinen, E., Sparks, T.H. and Zalakevicius, M. (2004). Arrivai and departure dates. In: Moller, A.P., Fieldler, W. and Berthold, P. (eds) Birds and Climate Change. Advances in Ecologica! Research, 35, 1-31. Murphy, P.W. 1982. Early and Late dates for Summer and Passage Migrants in Suffolk 1950-1980. Suffolk Birds 1981, 35-47. Sparks, T.H. and Mason. C.E (2001). Dates of arrivais and departures of spring migrants taken from Essex Bird Reports 1950-1998. Essex Bird Report 1999, 154-164.

18


First and Last Dates of Migrant Birds in Suffolk

1950-2004

Table 1. First arrivai dates. Numbers of years of data in the 55-year (1950-2004) period, overall mean date and Standard déviation (SD) of date. The earliest and latest recorded calendar dates are given. The différence ("Diff") between mean dates for 1950-1977 and 1978-2004 is tested using two sample t-tests, significant results are shown in bold. Species are arranged in order of increasing mean date. Wheatear Stane Curlew Chiffchaff Greenshank Garganey Sand Martin Black Redstart Little Ringed Piover Sandwich Tern Whimbrel Swallow Willow Warbler Blackcap House Martin Yellow Wagtail Redstart Ring Ouzel Sedge Warbler Common Sandpiper Tree Pipit Common Tern Cuckoo Nightingale Whitethroat Grasshopper Warbler Whinchat Turtle Dove Little Tern Reed Warbler Osprey Lesser Whitethroat Garden Warbler Swift Wryneck Pied Flycatcher Curlew Sandpiper Arctic Tern Black Tern Wood Warbler Spotted Flycatcher Hobby Wood Sandpiper Nightjar Red-backed Shrike Fieldfare Redwing

54 52 37 17 41 54 17 30 49 36 54 54 34 54 54 54 36 55 16 52 45 54 53 52 52 53 54 46 53 21 54 54 55 26 34 16 30 34 34 54 31 33 51 40 47 40

mean date SD 16-Mar 8.3 18-Mar 10.5 18-Mar 7.3 23-Mar 30.2 24-Mar 10.4 24-Mar 11.2 25-Mar 15.4 26-Mar 14.9 27-Mar 13.0 29-Mar 15.2 30-Mar 8.3 30-Mar 6.6 01-Apr 16.1 02-Apr 11.9 02-Apr 7.7 04-Apr 8.7 04-Apr 14.8 06-Apr 6.6 07-Apr 31.1 08-Apr 7.8 09-Apr 7.0 10-Apr 7.6 12-Apr 5.0 13-Apr 5.7 14-Apr 7.3 16-Apr 10.3 17-Apr 7.3 18-Apr 4.2 18-Apr 6.7 19-Apr 14.1 19-Apr 6.1 19-Apr 7.7 9.4 22-Apr 22-Apr 16.4 26-Apr 11.9 27-Apr 31.4 28-Apr 27.7 29-Apr 11.6 30-Apr 10.5 7.4 02-May 03-May 26.8 9.1 03-May 08-May 5.7 8.4 12-May 10-Sep 21-Sep

22.5 12.7

Mean dates latest 1¡950-1977 1978-2004 Diff earliest 12-Mar - 6 . 5 19-Mar 1 l-Apr-52 25-Feb-90 18-Mar -0.7 19-Mar 13-Apr-71 20-Feb-60 06-Apr-62 04-Mar-66 28-Apr-94 29-Jan-50 26-Mar 23-Mar -2.7 15-Apr-80 28-Feb-73 17-Mar - 1 3 . 3 30-Mar 13-Apr-71 21-Feb-90 30-Apr-60 01-Mar-85 07-May-50 03-Mar-97 23-Mar - 8 . 7 31-Mar 21-May-50 06-Mar-69 07-Apr 25-Mar - 1 2 . 7 12-Feb-79 18-Apr-53 27-Mar - 7 . 0 03-Apr 08-Mar-04 28-Apr-87 27-Mar - 5 . 5 01-Apr 14-Apr-70/75 16-Mar-85 21-Apr-62 13-Jan-60 28-Mar - 9 . 9 07-Apr 18-Apr-76 17-Feb-98 29-Mar - 7 . 7 06-Apr 12-Apr-56 08-Mar-90 01-Apr 07-Apr 5.3 19-Apr-92 15-Mar-97 03-May-60 06-Mar-03 03-Apr - 6 . 2 24-Apr-54 09-Apr 22-Mar-02 25-May-56 03-Jan-59 03-Apr - 8 . 7 26-Apr-50 12-Apr 21-Mar-68 06-Apr - 7 . 3 13-Apr 26-Apr-53 26-Mar-80 08-Apr -2.3 11-Apr 22-Apr-54 14-Mar-90 10-Apr -2.4 13-Apr 27-Apr-54 03-Apr-91/02 15-Apr 12-Apr - 3 . 4 01-May-72 01 -Apr-59 10-Apr - 7 . 2 17-Apr 29-Apr-56 Ol-Apr-89/95 15-Apr -3.0 18-Apr 1 l-May-72 20-Mar-64 15-Apr - 5 . 4 20-Apr 04-May-60 01-Apr-94 19-Apr 17-Apr -2.2 26-Apr-72 08-Apr-89 15-Apr - 7 . 2 22-Apr 05-Apr-80/89 01 -May-50 & 62 20-May-56 29-Mar-86/97 18-Apr -2.8 20-Apr 02-May-70 04-Apr-59 17-Apr - 5 . 1 22-Apr 04-May-70 03-Apr-02 15-Apr - 1 0 . 2 26-Apr 16-Mar-83 05 -May-57 & 79 21 -May-54 29-Mar-02 22-May-59 04-Apr-58 25-May-60 19-Jan-53 28-Jul-60 06-Apr-99/03 1 l-Jun-56 08-Apr-67 29-May-53 13-Apr-95 30-Apr - 5 . 5 05-May 16-May-57 09-Apr-83 20-Apr - 4 1 . 1 29-Jul-59 31-May 10-Apr-97/04 20-May-56 16-Apr-83 08-May 07-May -0.5 15-May-80 17-Apr-04 18-May 8.6 08-Jun-91 09-May 27-Apr-56 21-Jul-1963 03-Aug-1953

19

31-Oct-1952 17-Oct-1958

12-Sep 22-Sep

9-Sep 21-Sep

-2.3 -1.2


Suffolk Bird Report

2005

Table 2. Last departure dates. Numbers of years of data in the 55-year (1950-2004) period, overall mean date and Standard déviation (SD) of date. The earliest and latest recorded calendar dates are given. The différence ("Diff") between mean dates for 1950-1977 and 1978-2004 is tested using two sample t-tests, significant results are shown in bold. Species order as Table 1.

mean date SD 02-Nov 14.0 19-Oct 21.5 26-Oct 22.5 28-Oct 22.1 25-Sep 22.8 24-Oct 16.4 06-Nov 15.6 16-Sep 19.8 16-Oct 18.5 12-Oct 22.0 25-Nov 13.9 14-Oct 16.5 30-0ct 24.9 23-Nov 12.6 14-Oct 13.1 23-Oct 12.5 05-Nov 12.1 09-0ct 17.2 21-Oct 18.9 27-Sep 16.2 25-Oct 12.8 22-Sep 11.7 10-Sep 21.0 11-Oct 19.6 12-Sep 14.0 17-Oct 17.3 14-Oct 15.2 24-Sep 19.4 17-Oct 13.3 07-0ct 17.6 09-0ct 11.0 14-Oct 18.4 17-Oct 19.6 27-Sep 18.9 05-0ct 15.4 06-0ct 20.0 15-Oct 19.7 29-Sep 20.0 10-Sep 18.7 06-0ct 9.2 06-0ct 27.0 29-Sep 21.0 12-Sep 16.3 21-Sep 17.2

Wheatear Stone Curlew Chiffchaff Greenshank Garganey Sand Martin Black Redstart Little Ringed Piover Sandwich Tern Whimbrel Swallow Willow Warbler Blackcap House Martin Yellow Wagtail Redstart Ring Ouzel Sedge Warbler Common Sandpiper Tree Pipit Common Tern Cuckoo Nightingale Whitethroat Grasshopper Warbler Whinchat Turtle Dove Little Tern Reed Warbler Osprey Lesser Whitethroat Garden Warbler Swift Wryneck Pied Flycatcher Curlew Sandpiper Arctic Tern Black Tern Wood Warbler Spotted Flycatcher Hobby Wood Sandpiper Nightjar Red-backed Shrike

36 41 39

Fieldfare Rcdwing

45 22-May 43 9-May

54 46 34 17 39 55 14 33 48 36 55 53 32 55 53 53 34 51 16 47 43 53 46 51 40 54 51 46 52 21 52 51 55 28 35 16

28 35 27 52 31

25.5 18.7

earliest 09-Sep-51 15-Sep-82 12-Sep-02 19-Sep-94 17-Aug-54 22-Sep-01 24-Sep-50 02-Aug-56 20-Aug-54 18-Aug-50 07-0ct-50 17-Sep-73 07-Aug-51 lO-Oct-52 17-Sep-50 24-Sep-50/55 09-Oct-55 16-Sep-95 10-Sep-50 12-Aug-73 l9-Sep-69 28-Aug-66 01-Aug-67 05-Sep-50 12-Aug-95 01-Sep-51 09-Sep-53 09-Aug-50 17-Sep-55 05-Sep-58 19-Sep-67 1l-Sep-73 09-Sep-51 23-Aug-50 08-Aug-53 10-Sep-53 1O-Sep-55 27-Aug-50 04-Aug-52 15-Sep-70 21 -Jul-51 25-Aug-60 09-Aug-03 18-Aug-75 23-Apr-58/02 18-Mar-50

20

Mean dates latest 1950-1977 1978-2004 Diff 29-Nov-OO 28-Oct 08-Nov 11.5 31-Dec-53 25-Oct 15-Oct -10.0 13-Dec-72 16-Dec-55 09-Nov-92 07-Sep 04-0ct 2 7 . 5 09-Dec-51 22-Oct 26-Oct 3.4 25-Nov-84 27-Oct-83 13-Dec-00 05-0ct 25-Oct 2 0 . 2 27-Nov-99 26-Sep 18-Oct 2 1 . 3 16-Dec-56/00 24-Nov 26-Nov 1.2 16-Nov-82/94 04-0ct 24-Oct 19.1 07-Dec-74 17-Dec-71 22-Nov 24-Nov 1.8 16-Nov-03 08-0ct 20-0ct 12.7 22-NOV-75 19-Oct 26-Oct 6.5 26-Nov-95 08-Dec-85 07-0ct 10-Oct 2.6 02-Dec-51 02-NOV-04 18-Sep 05-0ct 17.7 16-NOV-77 25-Oct 25-Oct 0.5 17-Oct-98 18-Sep 25-Sep 6.3 19-NOV-93 05-Sep 15-Sep 9.7 07-Dec-91 02-0ct 21-Oct 1 8 . 3 04-Oct-93 09-Sep 14-Sep 5.2 08-Dec-81 08-0ct 28-Oct 2 0 . 0 25-NOV-68 lO-Oct 17-Oct 7.2 18-NOV-73 24-Sep 23-Sep -1.1 02-Dec-94 09-0ct 24-Oct 14.8 18-Nov-OO 08-NOV-90 02-0ct 16-Oct 13.8 13-NOV-88/00 02-0ct 26-Oct 2 4 . 7 09-Dec-74 13-Oct 21-Oct 8.0 08-NOV-86 07-NOV-82

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First and Last Dates of Migrant Birds in Suffolk

1950-2004

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Suffolk Birci Report 2005

Sep 15 O

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Figure 3. Mean change (days) between the two halves of the study for 29 autumn departures plotted against mean last departure date. Species above the line left later in the more recent period.

Year Figure 4. Last departure dates of Spotted Flycatcher in Suffolk 1950-2004. The thick grey line is a distance weighted smoothed (LOWESS) line emphasising the underlying trend. 22


First and Last Dates of Migrant Birds in Suffolk

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Suffolk Birci Report 2005

Pomarine Skuas Over-wintering off the North Suffolk Coast 1993-2005 Peter Dare and Paul Read Among skua connoisseurs the Pomarine Skua Stercorarius pomarinus is arguably the most fascinating of the four European species on account of the huge (almost legendary) numbers that may occur in the North Sea in autumn after particularly good breeding seasons. Major influxes involve several thousand skuas (mainly juveniles) and these 'good Pom years' are awaited eagerly by many east coast sea-watchers. This nomadic skua of the Siberian tundra in summer requires, and searches for, regions of high lemming abundance before it breeds. Lemmings are noted, of course, for their highly cyclical population fluctuations. After the breeding season, many Pomarines from the western Palaearctic population first migrate west around Norway and then south to winter in West African waters. Most take the direct Atlantic route west of the British Isles, while a highly variable number pass down the Baltic Sea, North Sea, and English Channel (Cramp & Simmons 1983; Olsen & Larsson 1997). Others fly south over Russia and Asia Minor to winter in the Arabian Sea, in another biologically rich upwelling region (Olsen & Larsson 1997). Pomarine Skuas also breed across east Siberian and North American tundras as far east as Baffin Island by the Labrador Sea. Many Nearctic birds travel down the western Atlantic to winter in the Caribbean region. There is no evidence for trans-Atlantic crossings to British coasts although, given that Sabine's Gulls from north-east Canada do so each autumn, occasional visits from Nearctic Pomarine Skuas are not inconceivable. In the North Sea, some of the more recent major Pomarine Skua influxes have been correlated with particularly successful breeding productivity in summers of high lemming abundance, sometimes followed by a particular autumnal sequence of weather patterns in the northern North Sea. The latter may involve initially stable anticyclonic conditions thought to induce birds to stay and feed before a breakdown to northerly gales drives them south and close to shore, as occurred in November 1985 (Fox & Aspinall 1987). In that year many hundreds were seen in eastern England, and 200(M1000 along the Dutch coastline (Camphuysen & van Ijsendoorn 1988a). More recent though smaller influxes onto southern North Sea coasts occurred in October 1997 and November 1999 (county bird reports). In Britain and north-west Europe in general, this skua has long been regarded as rarely occurring in winter (Olsen & Larsson 1997; all county bird reports). However, it is now known that, especially (though not exclusively) after some influx autumns, a few immature, and predominantly juvenile, Pomarines may linger through December and then over-winter among gull flocks in certain 'soft coast' localities. This happened most notably in the inner Moray Firth, Firth of Forth and Thames Estuary (Kent-Essex) during winter 1985/86 when groups of up to 20-35 skuas were present (Fox & Aspinall 1987). Otherwise, since then there have been scattered sightings in most winters of one to four birds from here and there down the east coasts of Scotland and England (county bird reports). In Suffolk, too, genuine winter (defined below) occurrences of Pomarine Skuas always had been rare prior to 1985, with just four records between 1963 and 1983 - all in late December or early January (Piotrowski 2003). The great 1985 autumn influx resulted in 11 birds being noted that winter in late December: nine south off Lowestoft on 26th, an adult off Benacre 'all month' and an immature eating a gull carcase at the Orwell Estuary on

24


Pomarine Skuas Over-wintering

off the North Suffolk Coast

1993-2005

29th (Fox & Aspinall 1987, Piotrowski 2003). However, there was no evidence of birds over-wintering in Suffolk waters, whereas many did so off Essex and Kent. In Norfolk, 11 single skuas (some duplication likely) were reported in January 1986 (Norfolk Bird Report) but all appeared to have been transients. In Suffolk since 1990, winter Pomarines have become more frequently reported, possibly due to increased sea-watching effort at this season (Piotrowski 2003). In winter 1999/2000 when a remarkable 25-30 occurred at times along the Suffolk coast from December to April, this event was well documented (Suffolk Bird Report 2000). We observed many of these skuas almost daily through the 1999/2000 winter as part of our long-term systematic recording of seabird movements off the coast of north Suffolk (Dare 1998a, Dare 1998b). A few Pomarine Skuas had been recorded by one of us (PJD) also in most other winters since October 1993. Here, we summarise observations of skua numbers and age compositions in this and the other 12 winters since 1993, and then relate them to records from around the coast of East Anglia, from the Wash to the Thames Estuary, and from further afield. Our observations on the foraging behaviour of wintering Pomarines during 1993 - 2005 are described elsewhere (Dare & Read, in press.). Methods For present purposes 'winter' is defined as the period between the winter solstice (December 20/21st) and the spring equinox (March 20/21st). Skuas seen earlier in December are regarded as more likely to have been late passage birds, though some were potential over-winterers. Birds seen later in March and April are also considered to have over-wintered, as the true spring migration of adult Pomarines, up the Channel and past south-east England, does not start before mid/late April. Our two watch points, at Kessingland (PR) and Covehithe (PJD), are respectively 6 km and 10 km south of Lowestoft. At Kessingland, where recording started in 1998, daily 2-5 hour winter watches were split more or less evenly between mornings and afternoons. The Covehithe watches, which began in October 1993, were usually for 1-3 hours in early mornings on three or more days each week until 2002, but less frequently since then. Observations from both sites are integrated for this analysis. Accurate counts were not always possible, especially in the 1999/2000 influx winter, because many skuas ranged north and south each day along the Suffolk coastline while searching for the mobile feeding flocks of Kittiwakes and larid gulls, which were their target species (Dare & Read, in press). However, our intensive observations enabled us to estimate the number of different individuals we saw each day during winter and those staying into early spring, based on plumage differences, timings and flight directions. Records from elsewhere were taken from county annual bird reports to compile highest day-counts within successive five-day periods at each site in Suffolk, and for each adjacent county. Some duplication of sightings is inevitable between sites when records for concurrent dates were not always available. Observations 1. 1993/94 to 1998/99 winters; Kessingland-Covehithe Wintering skuas were first noted by us off Covehithe in January 1994. Table 1 shows the annual variations in numbers; data refer to the highest day-count of individual birds (not sightings) for each month. The exceptional numbers present off Suffolk through winter 1999/2000 are reflected also in our local area counts (and see below). At least 90% of all birds seen were first-winter immatures, the rest being classed as older immatures with (rarely) a possible pale phase adult in non-breeding plumage. With records in ten of the last 25


Suffolk Birci Report 2005 12 winters, albeit often in small numbers, it is clear that Pomarine Skuas nowadays are not unusual off the Suffolk coast at this season. Some over-winter locally in certain years, while other individuals may visit sporadically from (as yet) unknown wintering areas in the North Sea (see below). The latter probability is indicated by the sudden influx of immature Pomarines in mid-April 1994 (Table 1). This included nine birds (eight first-winters and a sub-adult) moving north on 16th, with many other seabirds, after five had passed north on 13th, and ones or twos on other mornings (some duplication between days is possible). It contrasted with the few Pomarines Seen here over the preceding winter months. This event occurred during a period of strong northerly winds and suggested a 'relatively locai' origin further north in the North Sea. Such movements should not be confused with the true spring passage, of adult Pomarines, which, very occasionally, is seen off Suffolk in May.

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Pomarine Skuas Over-wintering

off the North Suffolk Coast

1993-2005

In most of these recent winters, apart from 1999/2000 (see below), only occasional Pomarine Skuas were reported elsewhere off Suffolk (SBRs), Norfolk (Table 2; NBRs), Essex (EBRs) and north Kent (KBRs). Further north, winter Pomarines remained a rare sight; for example, four singles over six winters in Lincolnshire (LBRs). In Yorkshire just one or two mid-winter records have occurred in most years since the 1970s (Wilson & Slack 1996). Thus, even at Flamborough Head only ten birds were seen during January-March over six of the winters between 1993 and 2001 (Flamborough Ornithological Group Reports). A similar scarcity prevailed in eastern Scotland during 1987 to 2002, and none was seen there in March (Scottish Bird Reports).

2. 1999/2000 winter influx: Suffolk Events in this winter were so unusual that a full analysis is given here. In November 1999, a record autumn passage of at least 675 Pomarine Skuas (mainly juveniles) had occurred off Norfolk (Table 2), including 435 past Sheringham on two November days (NBR 1999); but only eight in December. Off Suffolk, far smaller numbers were seen, including a November total of just ten juveniles at Kessingland and 17 further south at Thorpeness (SBR). From mid-December onwards, however, numbers off Suffolk increased rapidly to a record winter level (Figure 1). By January 7th an estimated 23-30 birds had congregated close inshore between Lowestoft and Aldeburgh; 21 of these were foraging along a 13 km stretch of Sole Bay from Dunwich southwards (SBR). There, on January 6th, one of us (PJD) observed at least ten Pomarine Skuas (eight first-winters, one subadult, one possible pale-phase adult) incessantly harassing hundreds of Kittiwakes (Rissa tridactyla) and Common Gulls (Larus canus) feeding at the outfall upwelling of Sizewell nuclear power station at Sole Bay. In our study area the skuas at first exploited mainly Kittiwakes, attracted to shoals of sprat (Sprattus sprattus) in January, and then switched to Common Gulls and larger larids later in the winter (Dare & Read, in press). The changing numbers of foraging skuas between Covehithe and Kessingland reflected an overall bimodal pattern evident for Suffolk and the East Anglia region (Figure 1 ). Thus, we saw most skuas in late December (up to ten different birds in a day) and again in late February and early March (up to 13 birds daily). They were scarcest (1-2 per day) in mid and late January, when numbers in the Thames mouth were highest (Figure 1, and below). This suggests a southerly dispersal from Suffolk of some skuas, though the whereabouts of others was not evident. All our sightings were of first-winter birds except for occasional views from February onwards of a 'sub-adult' with paler head and large white ventral area. In early March, the population comprised 12 first-winters (at least), a second-winter, an older immature ('sub-adult') and an apparent winter-plumaged adult. By mid-February, when most Kittiwakes had left Suffolk coastal waters, local skua numbers fell to the lowest level (Figure 1) but increased again from late February until mid-March when some 15-20 birds were again present (Figure 1). The last double-figure count was on March 14th when 16 flew north off Lowestoft (SBR). In south Suffolk, one or two birds lingered off Landguard Point until April 14th (www.birdguides.com), while the last bird was off Kessingland next day. None was then seen until mid-summer when single first-summer (second calendar-year) immatures appeared off Covehithe and Kessingland on six dates between June 23rd and July 15th, and three were off Thorpeness on July 9th (SBR); probably birds returning from the Thames area (see below). A typically sparse autumn passage began in late August 2000 and few sightings were made in the 2000/01 winter (Table 1). During the 1999/2000 winter, two other skua species were seen intermittently in our 27


Suffolk Birci Report

2005

area: a dark Arctic Skua (S. parasiticus) on nine dates in late December 1999 and three single Great Skuas (S. skua) passing through in late December and January. IA A

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Pomarine Skuas Over-wintering

off the North Suffolk Coast

1993-2005

3. 1999/2000 winter influx: nearby counties In Norfolk surprisingly few Pomarine sightings (just ones and twos) were reported during this winter, even in Mareh when they were numerous off Suffolk (Table 2; NBRs). North of the Wash no Pomarine Skuas appear to have been reported from Lincolnshire and only four sightings in Yorkshire - at Flamborough Head (Flamborough Ornithological Group Report 2000), In contrast, there were considerable two-way movements between Suffolk and the Thames area, where two or three skuas had been present between Essex and north Kent since mid-December (Figure 1). In late January, numbers increased in the Thames mouth between Sheppey and Foulness, but were difficult to assess due to considerable skua mobility and fragmentary reporting. They probably peaked at 15 birds (including an adult) during a short-lived influx in Kent on January 23rd (KBR, EBR, D.L.Davenport, pers. comm.). These birds soon departed, however, and only occasional birds were then reported through February and March. In fact, few skuas were seen anywhere in East Anglia for 3-4 weeks from late January, which indicates that most had moved offshore; after which 15 to 20 birds reappeared off Suffolk for three weeks from late February (Figure 1). Soon after this departure of Suffolk winter birds, some skuas began to appear again in the Thames mouth from mid-April. By April 28th at least ten birds (including an adult and a second-winter) had settled on the river itself at Cliffe in Kent. From these, a group of six (four first-summers, a second-summer and an adult in 'poor' (moult?) condition stayed into June. The four first-summer birds subsequently over-summered into July, with three of them staying until August 30th (KBR, D.L. Davenport,pers. comm.). On several occasions the summering Pomarines attacked Rooks (Corvus frugilegus) flying across the Thames between their feeding grounds in Essex and nesting colony in Kent. Along the English Channel coast of Kent, no more than three skuas were noted intermittently in January and early February; presumably birds moving around from the Thames group. After their memorable 1985 autumn influx, many Pomarines had subsequently over-wintered around the Thames mouth, which became the premier winter site in Britain (Fox & Aspinall 1987). There, a flock of 35 skuas had gathered by December 15th off Southend (EBR). In January 1986, an estimated 30-50 birds were present in this región, including 20 along the entire north coast of Kent (D.L.Davenport, pers. comm., KBR, EBR). 4. 1999/2000 winter: Belgium, Holland and Germany Extremely few skuas over-wintered along the southern coast of the North Sea. One or two did so (unusually) at Helgoland in the Germán Bight (Dierschke & Daniels 2002). No firm information is yet available from Holland or Belgium where, too, Pomarines are rarely noted in winter. Even after the massive 1985 influx, no more than a dozen birds stayed in Holland until December and apparently just one or two were seen later that winter (Camphuysen & van Ijsendoorn 1988b). In the 1994/95 winter, small numbers of both Pomarine and Great Skuas were recorded along the Dutch coast in early January (Dutch Birding 1995) and 12 Pomarine Skuas (with 56 Great Skuas) passed Oostende on January 2nd during northerly gales (Driessens 1995). In the other ten winters from 1993/94 to 2003/04, however, there appear to have been sightings in January or February of only three Pomarines in Belgium and one in Holland (Dutch Birding reports). 5. Pomaríne Skuas at Helgoland in summer 2000 Soon after the departure of most skuas from Suffolk, in March, and the Thames mouth area in early May, an exceptional influx of immature Pomarines began at Helgoland in the Germán Bight. There, after one or two birds had been seen intermittently from January to

29


Suffolk Birci Report 2005 May, numbers built up rapidly to a peak of 16 birds by mid-July before gradually moving away by mid-September (Dierschke & Daniels, 2002). Most were immatures in their second (11) or third (4) calendar-years with moulted primaries, tail feathers and wing coverts. One bird was adult. The skuas fed mainly by robbing Kittiwakes bringing food to a breeding colony. The correspondence between events on the Suffolk - Kent coasts and those in the German Bight - in terms of dates, skua numbers and âge compositions - is intriguing. It suggests that some immatures from our area may have moved north-eastwards 460 km towards their future breeding grounds. Discussion Winter numbers and ages: Before 1985 Pomarine Skuas were rarely seen in winter around British coasts. However, this analysis shows an upsurge in winter records off in

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Pomarine Skuas Over-wintering

off the North Suffolk Coast

1993-2005

Suffolk since unprecedented numbers over-wintered in the Thames mouth area in winter 1985/86. In both these areas winter sightings are nowadays not unusual and the 1999/2000 mid-winter (January) numbers off Suffolk, apparently, were the second highest yet reported in Britain. It appears that significant numbers over-winter only following some of the autumns, such as 1999 (and 1985), when there has been a large and late juvenile passage down the east coast in November. In other years, such as 1997, when there was a large passage (465 birds) off Norfolk in October (Table 2), very few skuas stayed into winter - one sighting off Suffolk (January), none in Essex or Kent, though seven sporadic sightings of singles in Norfolk. However, Pomarine Skuas may also winter far offshore in the North Sea (see below) and only occasionally come within sight of shore observers. Thus, whether these shore-based data represent a real increase and change in skua behaviour, or merely reflect skuas having been overlooked before the great increase in sea-watching effort over the last 15 years (Piotrowski 2003), is debatable. The Pomarine Skuas in our area were probably all immatures, predominantly first-winters with a few second-winters and third-winters ('sub-adults'), but no certain adults in winter plumage were confirmed. Their 1999/2000 over-winter survival appeared to be good, when comparing the maximum counts off north Suffolk in March (15-20) with those in early January (c.25) and allowing for other birds scattered elsewhere. Inshore wintering: The skuas off Suffolk and the Thames mouth area, like those in the Moray Firth in 1985/86 (Fox & Aspinall 1987), associated with large flocks of Kittiwakes and other gulls attracted to dense shoals of sprat. These fish move closer inshore into shallow waters from Suffolk to north Kent from November to mid-February, but shoal sizes and locations (and those of dependent seabirds and fishing boats) vary widely between years (Johnson 1966). The sprats also then become more accessible when brought to the surface by tidal turbulence over banks or in ship wakes (Dare & Read, in press). In effect, for Pomarine Skuas and other fish-eaters, the Suffolk coastal waters could be regarded as the outer northern sector of a 'Greater Thames Estuary' ecosystem, with its approximate seaward limit extending from Lowestoft southwards to Foreness in east Kent. There could also be a link with sprat stocks further offshore in the Southern Bight of the North Sea, where large annual variations in abundance and biomass occur in winter (Anon 2004). The three winters since 1993, when Pomarine Skuas were most frequent off Suffolk (1993/94, 1994/95 and 1999/2000), all coincided with large peaks in sprat biomass in the North Sea. In years (1996, 1997 and 2002) when sprat biomass was low, few or no Pomarines were observed off Suffolk or elsewhere in the region (Table 1), although 12 storm-driven birds were seen off the Belgian coast in January 1995 (see below). Another important factor could be that the south-east facing aspect of the Suffolk and Essex coast-line makes this the most sheltered stretch of North Sea coast from northerly gales in winter. In contrast, the larger sprat shoals that occur further north, from the Wash to Flamborough Head (Johnson 1970), are mostly in deeper and more exposed waters and apparently do not attract skuas. Sprat shoals also occur inshore along the English Channel coast from south Kent to Devon (Johnson 1966), but there, too, they are in deeper waters and off coasts exposed to winter storms; in this case mostly from between south and west. Pomarine Skuas are rarely reported there in winter, despite considerable observer coverage. Offshore wintering: Given that Pomarine Skuas are pelagic in winter off West Africa, it is possible that even in winters when few or none were seen off East Anglia coasts, some birds were wintering well offshore. This would explain the appearance of 12 Pomarines at Oostende, Belgium, on January 2nd 1995, during severe N-NW gales (Driessens 1995),

31


Suffolk Birci Report

2005

though none was seen anywhere in East Anglia at that time (Tables 1, 2). One large region, where Pomarine Skuas could over-winter undetected by shore observers, extends from off the Friesian coast, northern Holland, westwards close to East Anglia. In those waters (see map, Figure 2) large sprat concentrations return offshore in late winter, prior to spawning, and support large fisheries by March (Anon 2004). Indeed, seven Pomarines have been reported there during surveys in December-January and two others in February-March (Camphuysen & Leopold 1994). Demersal fisheries also occur in this region. Pomarines (as Great Skuas) thus could scavenge among and exploit the tens of thousands of Kittiwakes and other gulls, which here attend fishing vessels for discarded small fish and offal (Camphuysen el al., 1995). As, indeed, Pomarine flocks do off West Africa in winter (Cramp & Simmons 1983) and small numbers feed similarly off Spain during autumn passage (Valeiras 2003). Thus, the 'anomalous' April 1994 influx of wind-driven

Figure 2. The January-March distribution of sprat stocks and fisheries in the southern North Sea associated with over-wintering Pomarine Skuas; the major area is cross-hatched (redrawn from Anon 2004). The Wash to Flamborough sprat region is not shown. Places in text are: A - Aldeburgh, C - Covehithe, F - Foreness, FH - Flamborough Head, H - Helgoland, K - Kessingland, LP - Landguard Point, L - Lowestoft, O - Oostende, S - Shellness, TH - Thames Mouth, W - The Wash. Conclusions This analysis suggests that Pomarine Skuas over-wintering off the Suffolk-Thames coast are part of a variable population that remains in the southern North Sea in certain years. 32


Pomarine Skuas Over-wintering

off the North Suffolk Coast

1993-2005

Numbers and loca! distributions depend on a combination of biological and physical factors: (i) the strength and timing of the juvenile passage through the North Sea (in turn related to breeding season success and autumn weather conditions), (ii) the winter abundance and distribution of seabird victim species (related to seasonal movements of fish and associated fisheries), and for our coast (iii) shelter from strong northerly winds. Acknowledgements We are grateful to Steve Piotrowski and David Davenport for constructive comments on draft manuscripts; to the latter also for details of Pomarine Skuas in the Thames area; and to Dr Chris Darby (CEFAS, Lowestoft) for providing information on sprat stocks and fisheries. References Anon (2004). Sprat in the North Sea. International Council for the Exploration of the Sea, Herring Assessment Working Group, Report 2003, section 8. Camphuysen, C.J. & Ijsendoorn, E.J. van (1988a). Invasie van Middelste Jager in Nederland in November 1985. Dutch Birding, 10: 54-66. Camphuysen, C.J. & Ijsendoorn, E.J. van (1988b). Influx of Pomarine Skua in northwestern Europe in autumn 1985. Dutch Birding, 10: 66-70. Camphuysen, C.J. & Leopold, M.E (1994). Atlas of seabirds in the southern North Sea. IBN Research Report 94/6, NIOZ-Report 1994-8,, Texel, 126pp. Camphuysen, C.J., Calvo, B., Durinck, J., Ensor, K., Follestad, A., Furness, R.W., Garthe, S., Jeaper, G., Skov, H., Tasker, M.L. & Winter, C.J.N. (1995). Consumption of discards by seabirds in the North Sea. Final Report EC DG XIV research contract BIOECO/93/10. NIOZ Rapport 1995 - 5, Netherlands Institute for Sea Research, Texel, 240 pp. Cramp, S.C. & Simmons, K.E.L. (1983). The Birds of the Western Palearctic. Vol.3. Oxford University Press. Dare, P.J. (1998a). Seabird movements and abundance off Covehithe, Suffolk, 1994-96. 1. Fulmar, Gannet, Kittiwake, Guillemot and Razorbill. Suffolk Birds, Vol. 46: 16-36. Dare, P.J. (1998b). Movements and abundance of divers off Covehithe, Suffolk, 1994-96. Suffolk Birds, Vol. 46: 37- 47. Dare, P.J. & Read, P. (in press). Foraging behaviour of Pomarine Skuas over-wintering off the Suffolk coast. British Birds Dierschke, V & Daniels, J-P. (2002). Foraging behaviour of non-breeding Pomarine Skuas Stercorarius pomarinus in the North Sea in summer. Atlantic Seabirds, 4 (2): 53-62. Driessens, G. (1995). Recente meldingen Belgie Januari-Maart 1995. Dutch Birding 17: 85-87. Fox, A.D. & Aspirali, S.J. (1987). Pomarine Skuas in Britain and Ireland in autumn 1985. British Birds, 80: 404-421. Johnson, P.O. (1966). The English sprat fisheries. Annales biologiques, 23: 185-191. Johnson, P.O. (1970). The Wash sprat fishery. Fishery Investigations, Series 2, Vol. 26 (4), 77 pp. Olsen, K.M. & Larsson, H. (1997). Skuas and Jaegers. Pica Press, England. 190 pp. Piotrowski, S. (2003). The Birds of Suffolk. Christopher Helm, London. 360pp. Wilson, A. & Slack, R. (1996). Rare and scarce birds in Yorkshire. Guildford, Surrey. Valeiras, J. (2003). Attendance of scavenging seabirds at trawler discards off Galicia, Spain. Scientia Marina, 67 (Suppl. 2): 77-82. Dr Peter Dare, Glebe House, Toad Row, Henstead, Beccles, Suffolk NR34 7LG. Paul Read. High Deene, High Path, Kessingland, Suffolk NR33 7RS.

33


Suffolk Birci Report 2005

Baltic Gull in Suffolk Brian Small For a number of years there has been some discussion amongst gull enthusiasts about the status of the Baltic race of Lesser Black-backed Gull Larus fuscus fuscus, often termed 'Baltic Gull' (hereafter, the whole Lesser Black-backed Gull complex is referred to as LBbG and the other forms by their scientific names). Discussion has centred firstly on its identification, and this has then almost certainly aided in resolving its extralimital distribution. Subsequently, this has raised further questions about its taxonomic status, with some pushing for it to be split from the two other forms of LBbG, graellsii and intermedins. A number of recent studies of LBbG populations have questioned the precision with which it was once thought you could assign the three taxa to race. It was often done simply on the mantle tone of adults, which was thought to grade from the palest-grey form in the west (graellsii), eastwards through a darker grey or almost-black intermediate form (intermedins), to the almost black and darkest form in the Baltic region of Scandinavia (fuscus). This is a simplistic picture as there are one or two complications such as intergrade populations between graellsii and intermedius (like those on Orfordness, for instance). In general it was a widely held belief that the almost-black birds seen in Britain and Suffolk at various times of the year were intermedius. A quick check of my Suffolk Birds volume 46 (1996) shows various claims of fuscus from Covehithe and Minsmere from June or July of that year. However, Stuart Ling, who wrote the section on gulls, quite rightly pointed out the status of fuscus as a very rare migrant (thus raising questions as to the validity of the records). As time has passed by, and despite the increased awareness of the features of Baltic Gull, it is interesting to note that claims have dwindled to nothing. In ten years of intense watching, I have seen three birds that might have been fuscus in Suffolk, but, despite having one on video (which other experts agree, in all probability, is fuscus), the absolute proof is lacking or hard to confirm given the overlap in characters of intermedius and fuscus. Lars Jonsson's ground-breaking article in Birding World (1998) confirmed the difficulty involved in identifying Baltic Gull. As well as mantle tone there are other incredibly subtle elements, such as the timing of the moult, although even these are now questioned. As ever with gulls, further problems come in the form of non-adult birds. As a consequence, some concerns were raised by Jonsson about the validity of records of ringed fuscus in the UK. Using the theory that 'some birds ringed as fuscus as chicks have obviously been misidentified argentatus [Herring Gull] chicks', he went on to raise doubts as to the provenance of all five British ringing recoveries: 'the identity of all 12 reported recoveries of fuscus from the North Sea area can be questioned'. Some are questionable for the circumstances in which they were found and others for their date. The only acceptable ringing record of a fuscus in Britain concerns a fourth calendar-year bird ringed in Finland as a pullus in July 1978 and found off the Suffolk coast in October 1981. The full details of this recovery are as follows: Ringed Recovered

18.07.1978 24.10.1981

Porvoo, Uusimaa, Finland Orfordness, Suffolk

60째12'N 25째59'E 52째05'N 1째35'E

Jonsson writes of this record (and others), that the report lacks 'basic information regarding the circumstances of the findings and the exact localities are also very vague'. 34


Baltic Gull in Suffolk Despite these comments, this record has recently been fully examined by the British Ornithologists Union Records Committee (BOURC) and the following dĂŠcision reached: 'The committee has considered whether the nominate race of Lesser Bluck-bucked Gull L. f. fuscus, colloquialiy known as Baltic Gull, should be retained on the British List. On the basis of a Finnish bird ringed as a chick in July 1978 and recovered in Suffolk in October 1981, it was decided that it should but the Committee wish to draw the attention of observers to the extreme rarity of this taxon in Britaln.' So Baltic Gull has occurred in Suffolk, but what of any other claims? As far as I am aware, so far there have been no confirmed claims o f f u s c u s other than the 1981 bird, even though there is indeed a likelihood that they do occur. I am not sure if I can even give much guidance as to how to identify them; you would do much better to go to Jonsson's article, to the large number of websites with images of fuscus (and even only possible fuscus) in order to see the difficulty in positively identifying it, and also the recent 'Gulls' monograph (Mailing Olsen et al, 2003). There is, however, one way of being sure: find one with a colour ring fitted in the natal areas of Finland. It is pertinent to note that the Dutch Rarities Committee has for a while only accepted records of birds ringed in the breeding areas - a dĂŠcision that the British Birds Rarities Committee now follows. Finally, as I write (late May 2006) there is a colour-ringed fuscus near Amsterdam, Holland. They are out there . . . References Jonsson, L. 1998. Baltic Lesser Black-backed Gull Larus fuscus fuscus - moult, ageing and identification. Birding World V o l l 1, No.8, p.295-317. Mailing Olsen, K., and Larsson, H., 2003. Gulls of Europe and North America. Pica Press. Websites http://www.xs4all.nl/~daarruud/ http://www.xs4all.nl/~calidris/gullindex.htm http://www.magikbirds.com/image.asp7title id=781 &show thumbnails=True http://cvherbirding.uib.no/gull/ind lbbg.php

35


Suffolk Birci Report 2005

Minsmere RSPB Reserve 2005 Adam Rowlands, Senior Site Manager Habitat Following the construction of the bunds to compartmentalise the Scrape in autumn 2004, we were able to implement the fallowing project in summer 2005. It is intended to allow at least one compartment to dry out completely during the spring and vegetate over. This was achieved and the végétation was ploughed back into the soil using a tractor-mounted rotavator. The area is then re-flooded in the early autumn, in time to be colonised by aquatic invertebrates (predominantly Chironomid midge larvae). The aim of this project is to increase the invertebrate biomass for feeding waders and subsequently large numbers of Snipe and other waders were attracted to the plot on West Scrape during the autumn. We also used an excavator to create some new islands and shallow drains at the northern end of East Scrape and to improve the wetland viewing adjacent to the North and West hides, as part of our plans to bring birds closer to the hides. A Truxor floating reed-cutting machine was employed for the first time to clear areas of reed in the lowered areas, too deeply flooded to be cut by hand, further improving habitat for Bitterns. We also started work on the fen-restoration project in Meadow Marsh, a wetland area north-east of the Eastbridge meadows. An excavator was employed to clear choked ditches to provide 'wet fences' and enable grazing. This in turn will improve existing fen végétation and the habitat for invertebrates, along with providing feeding opportunities for Bitterns and hopefully benefit breeding Snipe. We also completed fencing work around the heath, to allow sheep grazing by our Manx Loghtans. North Country Cheviot sheep were used to graze the arable reversion areas and produced short, sparse swards, ideal for Wood Lark. A Konik filly was born in July - the first to be bred here at Minsmere. A large area of invading gorse on the arable reversion area was cleared. Visitors We were open seven days a week from Easter and visitor numbers have increased again this year, up 6% on the previous year. Our reception volunteers have done a fantastic job of recruiting new members, with a 21% increase in membership recruitment compared to last year. The guided walk programme continues to improve and our team of leaders, who also assist as "guides in hides", have done an excellent job, with many favourable comments from visitors. We also undertook a targeted mail drop to non-members and supporters in London and East Anglia, offering free entry and guided walks. This proved popular and assisted with attracting more visitors in the quieter winter months. We improved the surface of the trail along the north wall to the sea, so this path is now accessible to ali, allowing sea views. Open Access was introduced onto the main blocks of heathland on the reserve in the autumn. Ali the areas have restrictions, to ensure that dogs must be keep on a lead on Open Access land during the breeding season. This is to prevent disturbance to ground-nesting birds. Further areas will be closed entirely during the breeding season, to reduce disturbance to sensitive ground-nesting species. The importance of Minsmere as a démonstration site was further highlighted by Visits from professional conservationists from many European countries, as well as Japan, Turkey, Thailand, Nepal and South Korea during the course of the year. Birds and Biodiversity We saw another good season, with a number of breeding species responding to recent 36


Minsmere RSPB Reserve 2005 habitat management initiatives. A real highlight was the increase in Bittern numbers to ten booming males, with eight nesting females located. This equates to over 20% of the UK population of males and nearly 30% of females and shows that the intensive reedbed improvement work is really paying off. Marsh Harrier also achieved record levels (12 nests, which fledged 34 young). The Scrape work appeared to benefit Avocet, with 104 pairs fledging 36 young, the best season for a number of years. The management of the grazing marshes and Scrape, carried out to attract breeding waders, tempted 33 pairs of Lapwing to nest, almost certainly the highest number ever recorded on the reserve. Thirty-six pairs of Little Tern represented the best number for over ten years, but they failed to fledge any young. On the heath, Nightjar remained at 22 pairs, Wood Lark slipped to 15 pairs and Dartford Warbler increased to 27 pairs. New breeding species included Barnacle Goose (feral birds) and four pairs of Mediterranean Gull, which fledged two young. Stone Curlew nested again, following last year's first successful breeding in 35 years, but unfortunately the chicks did not survive to fledging. The birds are breeding on a sensitive area and there are presently no opportunities for public viewing. Last year's small curlew, thought by some to be a Slender-billed, was identified by Swedish scientists from DNA analysis of the droppings that had been collected and confirmed to be an abberant Eurasian Curlew. Rarities this year included a Marsh Sandpiper and Lesser Crested Tern (both second records for the site), along with Lesser Yellowlegs, White-winged Black Tern, Alpine Swift, Tawny Pipit and Bee-eater. An intensive study investigating the invertebrates in the reedbed continued and found good numbers of white-mantled wainscot moths, a species restricted to a short section of the Suffolk coast in the UK. We had a specialist survey of the Hymenoptera (bees and wasps) on the heathland, which found Bombus humilis, a bumblebee previously unknown in the area and only known from south Suffolk in the 1960s. The arrival of Harlequin ladybirds was less welcome, with a number of this alien species from Asia attracted to the moth trap. Moth trapping recorded 771 species, which included 94 species of leaf mining micro-moths discovered on a visit by John Langmaid, a number of which were new to the site and took the reserve moth list to 943! On the floral front, 170 red-tipped cudweed plants was an excellent record. Disasters & challenges The sea continĂşes to erode the dunes adjacent to north marsh. We had no major inundations, but the continued erosiĂłn is a concern. We are working with the Environment Agency and National Trust to find a management solution, but the good news is that a 37


Suffolk Birci Report 2005 major re-alignment across the reserve is not considered necessary for at least forty years. The spread of Pirri pirri bur, an invasive alien plant from New Zealand, continued around the car park. We were grateful for a number of volunteer work parties that helped us to collect the burs in an attempt to control the species and prevent it encroaching on heathland habitats. Looking forvvard We plan to complete the Meadow Marsh fen restoration project and introduce grazing stock during 2006. We are also looking to further improve the hydrological management on the grazing marshes on the levels, to provide further habitat for Lapwing and Redshank to nest. The long-term plans for management of the sea defences should be determined by the Environment Agency, providing protection for our breeding Bitterns. New visitor routes on the heath will be promoted, in conjunction with the Open Access land. By managing access, we should provide more opportunities to see birds such as Dartford Warbler and Wood Lark on the reserve, without causing increased disturbance to more sensitive areas. We intend to start work on plans to upgrade the visitor facilities on the reserve, including expanding the tea-room and improving the visitor centre, providing a classroom for school visits and a family friendly trail and picnic area. We also plan to replace the Island Mere hide and provide access for all to this facility.

38

Suffolk Birds 2005 Part 1  

Volume 55

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