BTO Research Report No. 683 Identification of Wintering Waterfowl High Tide Roosts on the Severn Estuary SSSI/SPA Phase 2 (Clevedon to Oldbury) & Phase 3 (Bridgwater Bay) Authors Woodward, I.D., Calbrade, N.A., Norfolk, D., Salter, A., Burton, N.H.K. & Wright, L.J. Report of work carried out by The British Trust for Ornithology under contract to Natural England August 2016 British Trust for Ornithology The British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU Registered Charity No. 216652 British Trust for Ornithology Identification of Wintering Waterfowl High Tide Roosts on the Severn Estuary SSSI/SPA Phase 2 (Clevedon to Oldbury) & Phase 3 (Bridgwater Bay) BTO Research Report No. 683 Woodward, I.D., Calbrade, N.A., Norfolk, D., Salter, A., Burton, N.H.K. & Wright, L.J. Published in August 2016 by the British Trust for Ornithology The Nunnery, Thetford, Norfolk, IP24 2PU, UK Copyright British Trust for Ornithology 2009 ISBN 978-1908581-71-6 CONTENTS Page No. List of Tables .......................................................................................................................................... 5 List of Appendices ................................................................................................................................ 11 EXECUTIVE SUMMARY ......................................................................................................................... 13 1. INTRODUCTION ....................................................................................................................... 15 1.1 Background ............................................................................................................................. 15 1.2 Species of concern .................................................................................................................. 16 2. METHODS ................................................................................................................................ 19 2.1 Approach and methods .......................................................................................................... 19 2.1.1 The Wetland Bird Survey (WeBS) .............................................................................. 19 2.1.2 Coverage of WeBS sectors ......................................................................................... 19 2.2 Methodology for sectors currently covered by WeBS volunteers ........................................ 19 2.3 Methodology for sectors not currently covered by WeBS volunteers ................................. 21 2.4 Consideration regarding the methodological approach ....................................................... 21 2.4.1 Difference of scale between different WeBS sectors/identifying roost sites ......... 21 2.4.2 Bird distribution on neap tides ................................................................................. 21 2.4.3 Accuracy of information in this report...................................................................... 22 2.5 Identification of Primary Roost sites ..................................................................................... 22 2.6 Outputs ................................................................................................................................... 23 3. RESULTS ................................................................................................................................... 25 3.1 Littleton Warth (WeBS sector 14454) .................................................................................... 25 3.1.1 Roost site 1A (The Pill) ............................................................................................... 25 3.1.2 Roost site 1B (Upstream of pill) ................................................................................ 26 3.1.3 Roost site 1C (Downstream of pill) ........................................................................... 26 3.1.4 Roost site 1D (Aust cliffs) .......................................................................................... 27 3.1.5 Comparison of roost site estimates with WeBS count data .................................... 28 3.2 Severn Beach Shore (WeBS sector 14451) ............................................................................. 29 3.2.1 Roost site 2A (Cake Pill, Aust Warth) ........................................................................ 30 3.2.2 Roost site 2B (Northwick Warth and flush) .............................................................. 31 3.2.3 Roost site 2C (Chestle Pill, New Passage) ................................................................. 32 3.2.4 Roost site 2D (Pilning Wetland) ................................................................................ 33 3.2.5 Roost site 2E (Shaft rocks) ......................................................................................... 34 3.2.6 Roost site 2F (Severn Beach Shore)........................................................................... 35 3.2.7 Roost site 2G (New Pill) ............................................................................................. 36 3.2.8 Roost site 2H (Stupp Pill, Chittening Warth) ............................................................ 37 3.2.9 Comparison of roost site estimates with WeBS count data .................................... 38 3.3 Severn – Avonmouth (WeBS sector 14408) ........................................................................... 39 3.3.1 Roost site 3A (Hole’s Mouth; Area A8) ..................................................................... 41 3.3.2 Roost site 3B (Area A9) .............................................................................................. 41 3.3.3 Roost site 3C (Area A6 and A7) ................................................................................. 42 3.3.4 Roost site 3D (Area A4) ............................................................................................. 42 3.3.5 Roost site 3E (Main Jetty; Area A3)........................................................................... 43 3.3.6 Roost site 3F (Under lighthouse, Area A2) ................................................................ 43 BTO Research Report No. 683 1 August 2016 Page No. 3.3.7 Roost site 3G (River Avon bank; Area A1a) .............................................................. 44 3.3.8 Comparison of roost site estimates with WeBS count data .................................... 44 3.4 Severn – M5 Bridge over River Avon (WeBS sector 14409) .................................................. 45 3.4.1 Comparison of roost site estimates with WeBS count data .................................... 45 3.5 Royal Portbury Docks (WeBS sector 14407) .......................................................................... 46 3.5.1 Comparison of roost site estimates with WeBS count data .................................... 46 3.6 Portbury Wharf (WeBS sector 14406) .................................................................................... 46 3.6.1 Roost site 6A (Chapel Pill; Area P1)........................................................................... 47 3.6.2 Roost site 6B (East Pier; Area R4) .............................................................................. 48 3.6.3 Roost site 6C (Areas R2 and R3) ................................................................................ 48 3.6.4 Comparison of roost site estimates with WeBS count data .................................... 49 3.7 River Avon – Sea Mills (WeBS sector 14415) ......................................................................... 50 3.7.1 Roost site 7A (Horseshoe Bend, Shirehampton) ...................................................... 50 3.7.2 Roost site 7B (Near Horseshoe Bend, Shirehampton) ............................................. 51 3.7.3 Roost site 7C (Near Sea Mills Harbour) ..................................................................... 51 3.7.4 Roost site 7D (Sea Mills Harbour) ............................................................................. 52 3.7.5 Roost site 7E (rocks) .................................................................................................. 52 3.7.6 Comparison of roost site estimates with WeBS count data .................................... 53 3.8 Severn – Battery Point (WeBS sector 14411) ........................................................................ 53 3.8.1 Roost site 8A (Battery Point) ..................................................................................... 54 3.8.2 Comparison of roost site estimates with WeBS count data .................................... 54 3.9 Battery Point to Redcliff Bay (WeBS sector 14412) ............................................................... 54 3.9.1 Roost site 9A (Woodhill Bay) ..................................................................................... 55 3.9.2 Comparison of roost site estimates with WeBS count data .................................... 55 3.10 Wain’s Hill to Charlcombe Bay (WeBS sector 14413) ............................................................ 56 3.10.1 Roost site 10A (Clevedon Marine Lake) .................................................................... 56 3.10.2 Roost site 10B (Clevedon Bay) .................................................................................. 57 3.10.3 Roost site 10C (Walton Bay) ...................................................................................... 57 3.10.4 Comparison of roost site estimates with WeBS count data