BTO Research Report No. 361 South West London Waterbodies SPA Wildfowl Population Analysis Authors A.N. Banks, G.E. Austin & M.M. Rehfisch A report by the British Trust for Ornithology to English Nature April 2004 © British Trust for Ornithology The National Centre for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU Registered Charity No. 216652 CONTENTS Page No. List of Tables...........................................................................................................................................3 List of Figures.........................................................................................................................................3 List of Appendices ..................................................................................................................................5 EXECUTIVE SUMMARY....................................................................................................................7 1. INTRODUCTION...................................................................................................................9 1.1 Aims..........................................................................................................................................9 2. METHODS ............................................................................................................................11 2.1 Data and Site Structure........................................................................................................11 2.2 Analysis..................................................................................................................................11 3. RESULTS ..............................................................................................................................15 3.1 Site Trends.............................................................................................................................15 3.1.1 South West London Waterbodies SPA................................................................15 3.1.1.1 Gadwall ..............................................................................................................15 3.1.1.2 Shoveler..............................................................................................................15 3.1.1.3 Tufted Duck........................................................................................................16 3.1.2 Regional and National Trends..............................................................................17 3.1.2.1 Gadwall ..............................................................................................................17 3.1.2.2 Shoveler..............................................................................................................17 3.1.2.3 Tufted Duck........................................................................................................17 3.1.3 Staines Moor SSSI .................................................................................................19 3.1.4 Knight and Bessborough Reservoirs....................................................................19 3.1.5 Thorpe Park Number 1 Gravel Pit ......................................................................19 3.1.6 Kempton Park Reservoirs ....................................................................................19 3.1.7 Wraysbury Reservoir............................................................................................20 3.1.7 Wraysbury & Hythe End Gravel Pits (including Yeoveney Lake and County Ditch Lake)........................................................................................20 3.1.9 Wraysbury Number 1 Gravel Pit.........................................................................20 3.1.10 Wraysbury Number 1 Gravel Pit (North)...........................................................20 3.1.11 Wraysbury Number 1 Gravel Pit (South) ...........................................................21 3.1.12 Wraysbury II (North) Gravel Pit.........................................................................21 3.1.13 Wraysbury II (South) Gravel Pit .........................................................................21 3.1.14 Yeoveney Lake.......................................................................................................21 3.1.15 County Ditch Lake ................................................................................................21 3.1.16 Wraysbury & Hythe End Gravel Pits (excluding Yeoveney Lake and County Ditch Lake)........................................................................................22 3.1.17 Wraysbury & Hythe End Gravel Pits (North & South) and Wraysbury Number 1 Gravel Pits................................................................22 3.1.18 ‘All winter months’ Alerts ....................................................................................22 3.2 Timing of Counts...................................................................................................................40 3.2.1 Staines Moor ..........................................................................................................40 3.2.2 Knight & Bessborough Reservoirs.......................................................................40 3.2.3 Thorpe Park Number 1 Gravel Pit ......................................................................40 3.2.4 Kempton Park Reservoirs ....................................................................................40 3.2.5 Wraysbury Reservoir............................................................................................40 BTO Research Report No. 361 1 April 2004 Page No. 3.2.6 Wraysbury & Hythe End Gravel Pits (including Yeoveney Lake and County Ditch Lake)........................................................................................41 3.2.7 Wraysbury Number 1 Gravel Pit.........................................................................41 3.2.8 Wraysbury Number 1 Gravel Pit (North)...........................................................41 3.2.9 Wraysbury Number 1 Gravel Pit (South) ...........................................................41 3.2.10 Wraysbury II (North) Gravel Pit.........................................................................41 3.2.11 Wraysbury II (South) Gravel Pit .........................................................................41 3.2.12 Yeoveney Lake.......................................................................................................41 3.2.13 County Ditch Lake ................................................................................................41 3.2.14 Wraysbury & Hythe End Gravel Pits (excluding Yeoveney Lake and County Ditch Lake)........................................................................................42 3.2.15 Wraysbury & Hythe End Gravel Pits (North & South) and Wraysbury Number 1 Gravel Pits .......................................................................42 3.2.16 South West London Waterbodies SPA................................................................42 4. CONCLUSIONS ...................................................................................................................59 4.1 SPA Species Trends ..............................................................................................................59 4.2 SSSI, Sector Level and Site Combination Trends..............................................................59 4.3 Timing of Peak Counts .........................................................................................................60 4.4 Future Research....................................................................................................................61 4.5 Specific Conclusions in Relation to Aims............................................................................61 Acknowledgements...............................................................................................................................63 References .............................................................................................................................................65 Appendices ............................................................................................................................................67 BTO Research Report No. 361 2 April 2004 List of Tables Page No. Table 3.1.1 Table of Alerts for 15 site consolidations and the SPA as a whole............................39 List of Figures Page No. Figure 3.1.1.1 Smoothed index for Gadwall on South West London Waterbodies SPA ..................15 Figure 3.1.1.2 Smoothed index for Shoveler on South West London Waterbodies SPA .................16 Figure 3.1.1.3 Smoothed index for Tufted Duck on South West London Waterbodies SPA ...........16 Figure 3.1.2 National and Regional smoothed GAM trends for Gadwall, Shoveler and Tufted Duck ...............................................................................................................18 Figure 3.1.3 Staines Moor SSSI. Site trends (‘Target consolidation’) shown for GA, SV and TU, with regional, national and SPA trends for comparison...............................24 Figure 3.1.4 Knight & Bessborough Reservoirs SSSI. Site trends (‘Target consolidation’) shown for GA, SV and TU, with regional, national and SPA trends for comparison.................................................................................................................25 Figure 3.1.5 Thorpe Park No. 1 Gravel Pit