Winter Gull Roosts in the United Kingdom in January 1993 with Recommendations for Future Surveys of Wintering Gulls
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BTO Research Report No. 277 Winter Gull Roosts in the United Kingdom in January 1993 With Recommendations for Future Surveys of Wintering Gulls Authors N.H.K. Burton, A.J. Musgrove, M.M. Rehfisch & A. Sutcliffe Report of work carried out by the British Trust for Ornithology under contract to English Nature October 2002 British Trust for Ornithology The National Centre for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU Registered Charity No. 216652 British Trust for Ornithology Winter Gull Roost In the United Kingdom In January 1993 With recommendations for Future Surveys of Wintering Gulls BTO Research Report No. 277 N.H.K. Burton, A.J. Musgrove, M.M. Rehfisch & A. Sutcliffe Published in October 2002 by the British Trust for Ornithology The Nunnery, Thetford, Norfolk, IP24 2PU, UK Copyright British Trust for Ornithology 2002 ISBN 1-902576-54-3 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 the prior permission of the publishers. CONTENTS Page No. List of Tables...........................................................................................................................................3 List of Figures.........................................................................................................................................5 List of Appendices ..................................................................................................................................5 EXECUTIVE SUMMARY....................................................................................................................7 1. INTRODUCTION .....................................................................................................................9 2. METHODS...............................................................................................................................11 2.1 Field Methods...........................................................................................................................11 2.2 Data Analysis ..........................................................................................................................11 2.2.1 Minimum Population Estimates and 1% Thresholds...........................................11 2.2.2 Comparison with Earlier Surveys ..........................................................................12 2.2.3 Assessment of the Representiveness of Single Counts ..........................................12 3. RESULTS.................................................................................................................................15 3.1 Coverage...................................................................................................................................15 3.2 Minimum Population Estimates and 1% Thresholds ..........................................................15 3.3 Comparison with Earlier Surveys..........................................................................................16 3.3.1 Comparison of Minimum Population Estimates...................................................16 3.3.2 Comparison of Counts at Individual Sites.............................................................17 3.4 Assessment of the Representativeness of Single Counts ......................................................17 4. DISCUSSION...........................................................................................................................19 5. RECOMMENDATIONS ........................................................................................................21 Acknowledgements...............................................................................................................................23 References .............................................................................................................................................25 Tables.....................................................................................................................................................29 Figures...................................................................................................................................................39 Appendices ............................................................................................................................................51 BTO Research Report No. 277 1 October 2002 BTO Research Report No. 277 2 October 2002 LIST OF TABLES Page No. Table 3.1.1 The numbers of inland and coastal sites covered by the 1953, 1963, 1973, 1983 and 1993 Winter Gull Roost Surveys ..................................................................29 Table 3.2.1 Minimum Population Estimates for Black-headed Gull, Common Gull, Lesser Black-backed Gull, Herring Gull and Great Black-backed Gull wintering in Great Britain, Northern Ireland, the Isle of Man and the Channel Islands, together with 1% Thresholds for Great Britain ............................................................30 Table 3.2.2 Sites which held at least 1% of the minimum Great Britain populations of Black-headed Gull, Common Gull, Lesser Black-backed Gull, Herring Gull and Great Black-backed Gull in January 1993 .............................................................31 Table 3.2.3 Sites which held at least 20,000 gulls in January 1993 ................................................34 Table 3.3.1.1 Minimum population estimates of wintering gulls at inland sites in England, Wales and Scotland in 1953, 1963, 1973, 1983 and 1993............................................35 Table 3.3.1.2 Minimum population estimates of wintering gulls at coastal sites in England, Wales and Scotland in 1983 and 1993..........................................................................36 Table 3.4.1 Coefficients of variation for counts of gulls at a. The King George V & William Girling Reservoirs and b. Chelford Farmwood Pool, between December and February................................................................................................37 BTO Research Report No. 277 3 October 2002 BTO Research Report No. 277 4 October 2002 LIST OF FIGURES Page No. Figure 3.2.1 Estimated numbers of gulls counted at inland sites in Great Britain in January 1993 ..............................................................................................................39 Figure 3.2.2 Estimated numbers of gulls counted at coastal sites in Great Britain in January 1993 ..............................................................................................................40 Figure 3.3.1.1 Numbers of gulls counted at inland sites in England during the 1953, 1963, 1973, 1983 and 1993 surveys, in relation to the number of sites surveyed and with roosts............................................................................................41 Figure 3.3.2.1 Numbers of Black-headed Gulls at roosts surveyed in 1953, 1963, 1973, 1983 and 1993............................................................................................................42 Figure 3.3.2.2 Numbers of Common Gulls at roosts surveyed in 1953, 1963, 1973, 1983 and 1993.....................................................................................................................43 Figure 3.3.2.3 Numbers of Lesser Black-backed Gulls at roosts surveyed in 1953, 1963, 1973, 1983 and 1993..................................................................................................44 Figure 3.3.2.4 Numbers of Herring Gulls at roosts surveyed in 1953, 1963, 1973, 1983 and 1993.....................................................................................................................45 Figure 3.3.2.5 Numbers of Great Black-backed Gulls at roosts surveyed in 1953, 1963, 1973, 1983 and 1993..................................................................................................46 Figure 3.4.1 Numbers of gulls roosting at the King George V & William Girling Reservoirs in the Lea Valley between 1957 and 1960...............................................47 Figure 3.4.2 Numbers of gulls roosting at Chelford Farmwood Pool in Cheshire in the winter of 1985/86.......................................................................................................48 Figure 3.4.3 Numbers of gulls roosting at Frampton & Waveridge Sands on the Severn Estuary between November 1988 and January 1993 .................................................49 LIST OF APPENDICES Page No. Appendix 1 Estimated numbers of gulls counted in the 1993 Winter Gull Roost Survey ...............51 Appendix 2 Estimated numbers of gulls counted in the 1983 Winter Gull Roost Survey ...............53 Appendix 3 Estimated numbers of gulls counted at inland sites in the 1973 Winter Gull Roost Survey.................................................................................................................59 Appendix 4 Estimated numbers of gulls counted at inland sites in the 1963 Winter Gull Roost Survey.................................................................................................................61 Appendix 5 Estimated numbers of gulls counted at inland sites in the 1963 Winter Gull Roost Survey.................................................................................................................62 BTO Research Report No. 277 5 October 2002 BTO Research Report No. 277 6 October 2002 EXECUTIVE SUMMARY 1. This report is in two