BTO Research Report No. 335 Low-Tide Distributions of Waterbirds on the Severn Estuary SPA: Results of the 2002/03 WeBS Low Tide Counts and a Historical Analysis Adroddiad Ymchwil Rhif 335 yr Ymddiriedolaeth Adareg Brydeinig Dosbarthiad Adar Dŵr pan fo hi’n ddistyll ar Aber yr Afon Hafren AGA : Canlyniadau AAyG 2002/03 o’r Cyfrifon Distyll Ynghyd ẩ Dadansoddiad Hanesyddol Authors Burton, N.H.K., Marchant, J.H., Musgrove, A.J., Armitage, M.J.S., Holloway, S.J. & Phillips, J. Report of work carried out by The British Trust for Ornithology under contract to English Nature and the Countryside Council for Wales November 2003 © British Trust for Ornithology, English Nature and the Countryside Council for Wales British Trust for Ornithology, The Nunnery, Thetford, Norfolk, IP24 2PU Registered Charity No. 216652 British Trust for Ornithology Low-Tide Distributions of Waterbirds on the Severn Estuary SPA: Results of the 2002/03 WeBS Low Tide Counts and a Historical Analysis BTO Research Report No. 335 Burton, N.H.K., Marchant, J.H., Musgrove, A.J., Armitage, M.J.S., Holloway, S.J. & Phillips, J. Published in November 2003 by the British Trust for Ornithology The Nunnery, Thetford, Norfolk, IP24 2PU, UK Copyright © British Trust for Ornithology, English Nature and the Countryside Council for Wales ISBN 1-902576-99-3 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......................................................................................................................................... 5 List of Figures ....................................................................................................................................... 7 Executive Summary............................................................................................................................ 13 PART 1 THE 2002/03 WEBS LOW TIDE COUNT SURVEY ..................................................... 17 1. INTRODUCTION................................................................................................................. 17 2. METHODS............................................................................................................................. 19 2.1 Count Sections and Survey Methodology............................................................................ 19 2.2 Coverage................................................................................................................................. 20 2.3 Data Presentation .................................................................................................................. 20 3. RESULTS OF THE 2002/03 WEBS LOW TIDE COUNTS OF THE SEVERN ESTUARY............................................................................................................. 23 3.1 Little Grebe Tachybaptus ruficollis ..................................................................................... 23 3.2 Great Crested Grebe Podiceps cristatus.............................................................................. 23 3.3 Cormorant Phalacrocorax carbo......................................................................................... 23 3.4 Bittern Botaurus stellaris...................................................................................................... 23 3.5 Little Egret Egretta garzetta................................................................................................. 24 3.6 Grey Heron Ardea cinerea ................................................................................................... 24 3.7 Mute Swan Cygnus olor ....................................................................................................... 24 3.8 Bewick's Swan Cygnus columbianus................................................................................... 24 3.9 Whooper Swan Cygnus cygnus............................................................................................ 25 3.10 European White-fronted Goose Anser albifrons albifrons................................................ 25 3.11 Greylag Goose Anser anser.................................................................................................. 25 3.12 Canada Goose Branta canadensis........................................................................................ 25 3.13 (Dark-bellied) Brent Goose Branta bernicla bernicla ........................................................ 25 3.14 Shelduck Tadorna tadorna ................................................................................................... 26 3.15 Wigeon Anas penelope.......................................................................................................... 26 3.16 Chiloe Wigeon Anas sibilatrix.............................................................................................. 26 3.17 Gadwall Anas strepera.......................................................................................................... 26 3.18 Teal Anas crecca ................................................................................................................... 27 3.19 Mallard Anas platyrhynchos ................................................................................................ 27 3.20 Pintail Anas acuta ................................................................................................................. 27 3.21 Shoveler Anas clypeata ......................................................................................................... 27 3.22 Pochard Aythya farina.......................................................................................................... 28 3.23 Tufted Duck Aythya fuligula................................................................................................ 28 3.24 Scaup Aythya marila ............................................................................................................. 28 3.25 Common Scoter Melanitta nigra.......................................................................................... 28 3.26 Goldeneye Bucephala clangula............................................................................................ 29 3.27 Goosander Mergus merganser ............................................................................................. 29 3.28 Water Rail Rallus aquaticus ................................................................................................ 29 3.29 Moorhen Gallinula chloropus .............................................................................................. 29 3.30 Coot Fulica atra .................................................................................................................... 29 3.31 Oystercatcher Haematopus ostralegus ................................................................................ 30 3.32 Avocet Recurvirostra avosetta .............................................................................................. 30 3.33 Ringed Plover Charadrius hiaticula .................................................................................... 30 3.34 Golden Plover Pluvialis apricaria........................................................................................ 31 3.35 Grey Plover Pluvialis squatarola ......................................................................................... 31 3.36 Lapwing Vanellus vanellus................................................................................................... 31 BTO Research Report No. 335 1 November 2003 Page No. 3.37 Knot Calidris canutus ........................................................................................................... 32 3.38 Sanderling Calidris alba ....................................................................................................... 32 3.39 Purple Sandpiper Calidris maritima..................................................................................... 32 3.40 Dunlin Calidris alpina........................................................................................................... 32 3.41 Jack Snipe Lymnocryptes minimus...................................................................................... 33 3.42 Common Snipe Gallinago gallinago.................................................................................... 33 3.43 Black-tailed Godwit Limosa limosa..................................................................................... 33 3.44 Bar-tailed Godwit Limosa lapponica................................................................................... 34 3.45 Curlew Numenius arquata ................................................................................................... 34 3.46 Spotted Redshank Tringa erythropus.................................................................................. 34 3.47 Redshank Tringa totanus ..................................................................................................... 35 3.48 Greenshank Tringa nebularia.............................................................................................. 35 3.49 Green Sandpiper Tringa ochropus...................................................................................... 35 3.50 Common Sandpiper Actitis hypoleucos............................................................................... 35 3.51