BTO Research Report No. 660 The Wash Bird Decline Investigation 2014 Authors Ian D. Woodward, Viola H. Ross-Smith, Rafael Pérez-Domínguez, Mark M. Rehfisch and Graham E. Austin Report of work carried out by The British Trust for Ornithology under contract to Natural England March 2015 British Trust for Ornithology The British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU Registered Charity No. 216652 British Trust for Ornithology The Wash Bird Decline Investigation 2014 BTO Research Report No. 660 Ian D. Woodward, Viola H. Ross-Smith, Rafael Pérez-Domínguez, Mark M. Rehfisch and Graham E. Austin Published in March 2015 by the British Trust for Ornithology The Nunnery, Thetford, Norfolk, IP24 2PU, UK Copyright British Trust for Ornithology 2015 ISBN 978-1-908581-52-5 CONTENTS Page No. List of Tables ...................................................................................................................................... 3 List of Figures ...................................................................................................................................... 5 EXECUTIVE SUMMARY ........................................................................................................................... 7 1 INTRODUCTION ................................................................................................................ 9 1.1 Background and aims ....................................................................................................... 9 1.2 Species of concern .......................................................................................................... 12 2 METHODS ...................................................................................................................... 15 2.1 Literature search ............................................................................................................ 15 2.2 Assessment of the evidence and ecological knowledge ................................................... 15 3 RESULTS ......................................................................................................................... 17 3.1 Waterbird accounts ........................................................................................................ 17 3.1.1 Dark-bellied Brent Goose ............................................................................................... 18 3.1.2 Shelduck ........................................................................................................................ 20 3.1.3 Mallard .......................................................................................................................... 23 3.1.4 Pintail ............................................................................................................................ 25 3.1.5 Oystercatcher ................................................................................................................ 27 3.1.6 Grey Plover .................................................................................................................... 31 3.1.7 Lapwing ......................................................................................................................... 34 3.1.8 Knot ............................................................................................................................... 37 3.1.9 Sanderling ...................................................................................................................... 40 3.1.10 Dunlin ............................................................................................................................ 43 3.1.11 Black-tailed Godwit ........................................................................................................ 46 3.1.12 Bar-tailed Godwit ........................................................................................................... 49 3.1.13 Curlew ........................................................................................................................... 52 3.1.14 Redshank ....................................................................................................................... 55 3.1.15 Turnstone ...................................................................................................................... 58 3.2 Food availability trends .................................................................................................. 61 3.2.1 Intertidal bivalve fishery resource abundance and distribution ........................................ 61 3.2.2 Mussels (Mytilus edulis) ................................................................................................. 61 3.2.3 Cockle (Cerastoderma edule) .......................................................................................... 62 3.2.4 Intertidal macrofauna abundance ................................................................................... 62 3.2.5 Intertidal macrofauna assemblages, biotopes and sediment type .................................... 64 3.2.6 Relevance of changes in intertidal macrofauna to bird numbers on The Wash ................. 64 3.3 Disturbance ................................................................................................................... 67 3.3.1 Activities causing disturbance ......................................................................................... 67 3.3.2 Impacts of disturbance ................................................................................................... 68 3.3.3 Potential disturbance activities on The Wash .................................................................. 71 3.4 Habitat Change .............................................................................................................. 74 3.4.1 Intertidal Mudflats ......................................................................................................... 74 3.4.1.1 Sewage inputs ................................................................................................... 75 3.4.1.2 The Great Ouse Outflow ..................................................................................... 75 BTO Research Report No. 660 1 March 2015 3.4.2 Saltmarsh ....................................................................................................................... 75 3.4.3 Managed Realignment ................................................................................................... 76 3.4.4 Sandy Beaches ............................................................................................................... 77 3.4.5 Lagoons ......................................................................................................................... 77 3.4.6 Coastal and Floodplain Grazing Marsh ............................................................................ 77 3.4.7 Inland Habitats ............................................................................................................... 77 3.5 Secto-level cross-tabulation of waterbird and environmental information ....................... 78 4 DISCUSSION ................................................................................................................... 85 4.1 Species Overviews .......................................................................................................... 85 4.1.1 Dark-bellied Brent Goose ............................................................................................... 86 4.1.2 Shelduck ........................................................................................................................ 87 4.1.3 Mallard .......................................................................................................................... 88 4.1.4 Pintail ............................................................................................................................ 89 4.1.5 Oystercatcher ................................................................................................................ 90 4.1.6 Grey Plover .................................................................................................................... 91 4.1.7 Lapwing ......................................................................................................................... 92 4.1.8 Knot ............................................................................................................................... 93 4.1.9 Sanderling ...................................................................................................................... 94 4.1.10 Dunlin ............................................................................................................................ 95 4.1.11 Black-tailed Godwit ........................................................................................................ 96 4.1.12 Bar-tailed Godwit ........................................................................................................... 97 4.1.13 Curlew ........................................................................................................................... 98 4.1.14 Redshank ....................................................................................................................... 99 4.1.15 Turnstone .................................................................................................................... 100 4.2 Conclusions .................................................................................................................