Assessing Habitat Use of Herring Gulls in the Morecambe Bay SPA Using GPS Tracking Devices
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BTO Research Report No. 693 Assessing habitat use of Herring Gulls in the Morecambe Bay SPA using GPS tracking devices Authors Chris B. Thaxter, Gary Clewley, Lee Barber, Greg J. Conway, Nigel A. Clark, Emily S. Scragg and Niall H.K. Burton British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK Report of work carried out by the British Trust for Ornithology on behalf of Natural England May 2017 British Trust for Ornithology The British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU Registered Charity No. 216652 British Trust for Ornithology Assessing habitat use of Herring Gulls in the Morecambe Bay SPA using GPS tracking devices BTO Research Report No. 693 Chris B. Thaxter, Gary Clewley, Lee Barber, Greg J. Conway, Nigel A. Clark, Emily S. Scragg and Niall H.K. Burton Published in May 2017 by the British Trust for Ornithology The Nunnery, Thetford, Norfolk, IP24 2PU, UK Copyright British Trust for Ornithology 2009 ISBN 978-1-908581-82-2 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 .................................................................................................................................. 7 EXECUTIVE SUMMARY ........................................................................................................................... 9 1. INTRODUCTION ....................................................................................................................... 11 1.1 Project Aims ............................................................................................................................ 11 1.2 Objectives ................................................................................................................................ 11 2. METHODS ................................................................................................................................ 13 2.1 Focal Species ........................................................................................................................... 13 2.2 Field Sites ................................................................................................................................ 13 2.3 Capture and Attachment Methods ........................................................................................ 13 2.4 The GPS System ...................................................................................................................... 14 2.4.1 GPS devices ................................................................................................................ 14 2.4.2 Sampling schedules.................................................................................................... 14 2.5 Defining Periods of the Year ................................................................................................... 14 2.6 Data Manipulation .................................................................................................................. 17 2.6.1 Sub-sampling data ..................................................................................................... 17 2.6.2 Indicative quality of filtered data .............................................................................. 17 2.7 Data Analysis ........................................................................................................................... 20 2.7.1 Space use .................................................................................................................... 20 2.7.2 Temporal use ............................................................................................................. 23 3. RESULTS ......................................................................................................................... 25 3.1 Data overview ......................................................................................................................... 25 3.2 Movement Modelling to Identify Resting and Foraging Locations ....................................... 27 3.3 Spatial Area Usage .................................................................................................................. 34 3.3.1 Spatial overlap of kernel density estimates with areas of interest ......................... 39 3.3.2 Temporal overlap with areas of interest .................................................................. 53 4. DISCUSSION ............................................................................................................................. 61 Acknowledgments ............................................................................................................................... 63 References ............................................................................................................................................ 65 BTO Research Report No. 693 May 2017 1 BTO Research Report No. 693 May 2017 2 LIST OF TABLES Page No. Table 2.1 Defined birds-specific winter periods ........................................................................ 15 Table 2.2 Periods of data acquisition for each Herring Gull tagged at South Walney, from Development to last date gathered ........................................................................... 16 Table 2.3 Upper and lower bounds of filtered GPS fixes falling within percentage categories, used in turn to indicate the quality of data ................................................................ 18 Table 2.4 Number of fixes from each Herring Gull tagged at South Walney ............................. 19 Table 3.1 Percentage overlaps of 50% and 95% KDEs for Herring Gulls tagged at South Walney with mussel bed shapefile 1 as provided by Natural England ...................... 41 Table 3.2 Percentage overlaps of 50% and 95% KDEs for Herring Gulls tagged at South Walney with mussel bed shapefile 2 as provided by Natural England ...................... 42 Table 3.3 Percentage overlaps of 50% and 95% KDEs for Herring Gulls tagged at South Walney with the Lune Estuary SSSI ............................................................................ 43 Table 3.4 Percentage overlaps of 50% and 95% KDEs for Herring Gulls tagged at South Walney with the Morecambe Bay SSSI ...................................................................... 44 Table 3.5 Percentage overlaps of 50% and 95% KDEs for Herring Gulls tagged at South Walney with the South Walney and Piel Channel Flats SSSI ...................................... 45 Table 3.6 Percentage overlaps of 50% and 95% KDEs for Herring Gulls tagged at South Walney with the Wyre Estuary SSSI ........................................................................... 46 Table 3.7 Percentage overlaps of 50% and 95% KDEs for Herring Gulls tagged at South Walney with the Morecambe Bay SPA ....................................................................... 47 Table 3.8 Are (km2) of 50% and 95% KDEs for Herring Gulls tagged at South Walney based On data filtered to 10 minute and 60 minute rates for the 2014 and 2015 Breeding (Br) and post-breeding (PoBr) periods and the 2015 pre-breeding Period (PrBr) ............................................................................................................... 48 Table 3.9 Percentage overlaps of 50% and 95% KDEs for Herring Gulls tagged at South Walney with (a) mussel beds and (b) the Morecambe Bay SPA and constituent SSIs .............................................................................................................................. 49 Table 3.10 Final summary of spatial values for (a) 95% KDE overlaps and (b) 50% KDE overlaps for the South Walney Herring Gull population ............................................ 52 Table 3.11 Percentage temporal overlap for Herring Gulls tagged at South Walney with the Mussel bed shapefile 1 as provided by Natural England ........................................... 54 BTO Research Report No. 693 May 2017 3 Page No. Table 3.12 Percentage temporal overlap for Herring Gulls tagged at South Walney with the Mussel bed shapefile 2 as provided by Natural England ........................................... 55 Table 3.13 Percentage temporal overlap for Herring Gulls tagged at South Walney with the Lune Estuary SSSI ........................................................................................................ 56 Table 3.14 Percentage temporal overlap for Herring Gulls tagged at South Walney with the Morecambe Bay SSSI .................................................................................................. 57 Table 3.15 Percentage temporal overlap for Herring Gulls tagged at South Walney with the South Walney and Piel Channel Flats SSSI .................................................................. 58 Table 3.16 Percentage temporal overlap for Herring Gulls tagged at South Walney with the Wyre Estuary SSSI ....................................................................................................... 59 Table 3.17 Final summary of temporal overlaps