BTO Research Report No. 515 Carrying Capacity Modelling for the Pied Oystercatcher at Lauderdale and Surrounding Sites. Lauderdale Quay Proposal. Authors Philip W. Atkinson1 & Richard A. Stillman2 1British Trust for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU, UK & 2School of Conservation Sciences, Bournemouth University, Talbot Campus, Poole, Dorset BH12 5BB, UK. November 2008 © British Trust for Ornithology & Bournemouth University Report prepared for Aquenal Pty Ltd British Trust for Ornithology, The Nunnery, Thetford, Norfolk, IP24 2PU Registered Charity No. 216652 British Trust for Ornithology Carrying Capacity Modelling for the Pied Oystercatcher at Lauderdale and Surrounding Sites. Lauderdale Quay Proposal. BTO Research Report No. 515 Philip W. Atkinson & Richard A. Stillman Published in … 2008 by the British Trust for Ornithology The Nunnery, Thetford, Norfolk, IP24 2PU, UK Copyright © British Trust for Ornithology 2008 ISBN 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 BTO Research Report No. 515 i November 2008 CONTENTS Page No. List of Tables ........................................................................................................................................iv List of Figures........................................................................................................................................v Executive Summary .............................................................................................................................vi 1. INTRODUCTION ...................................................................................................................1 1.1 Background to this study.........................................................................................................1 1.2. Overview of the model.............................................................................................................1 1.2.1 Application and testing the model to Eurasian Oystercatchers .............................2 1.2.2 Parameters required to apply the model to a new system.......................................2 1.2.3 Applying the model to Lauderdale and surrounding bays .....................................3 2. METHODS ...............................................................................................................................4 2.1 Study Sites ................................................................................................................................4 2.1.1 Site selection ................................................................................................................4 2.1.2 Division of the study sites into patches......................................................................5 2.2 Availability of Intertidal Feeding Habitat ............................................................................7 2.2.1 Introduction.................................................................................................................7 2.2.2 Methods........................................................................................................................7 2.2.2.1 Generating tide tables and bathymetry .........................................................................7 2.2.2.2 Ascertaining patch area available to birds ....................................................................8 2.3 Calculation of the Energy Content of the Invertebrate Prey.............................................11 2.3.1 Introduction...............................................................................................................11 2.3.2 Ash-Free Dry Mass Estimation................................................................................11 2.3.3 Results........................................................................................................................11 2.4 Foraging Studies ....................................................................................................................20 2.4.1 Introduction & methods...........................................................................................20 2.4.2 Results........................................................................................................................20 2.5 Parameterising the Model for Pied Oystercatcher .............................................................26 2.5.1 Single- and multi-bay models...................................................................................26 2.5.2 Environmental parameters ......................................................................................26 2.5.2.1 Time period simulated ................................................................................................26 2.5.2.2 Time step length..........................................................................................................26 2.5.2.3 Day length...................................................................................................................26 2.5.2.4 Tidal cycle...................................................................................................................27 2.5.3 Patch parameters ......................................................................................................27 2.5.3.1 Maximum patch area ..................................................................................................27 2.5.3.2 Patch area available to birds .......................................................................................27 2.5.4 Food resource parameters........................................................................................28 2.5.4.1 Prey size classes..........................................................................................................29 2.5.4.2 Numerical density of prey at start of each season.......................................................29 2.5.4.3 Prey mass during each season.....................................................................................29 2.5.4.4 Prey energy content ....................................................................................................30 2.5.5 Bird parameters ........................................................................................................30 2.5.5.1 Population size............................................................................................................30 2.5.5.2 Target body mass and starvation body mass...............................................................31 Continued…/ BTO Research Report No. 515 ii November 2008 Page No. 2.5.5.3 Energy density of bird reserves...................................................................................31 2.5.5.4 Metabolic rate .............................................................................................................31 2.5.5.5 Time and energy cost of moving between patches .....................................................31 2.5.5.6 Size ranges of prey diets consumed by the birds ........................................................31 2.5.5.7 Individual variation.....................................................................................................32 2.5.5.8 Day and night variation in foraging efficiency ...........................................................32 2.5.5.9 Interference competition .............................................................................................32 2.5.5.10 Functional response ...................................................................................................33 2.5.5.11 Maximum intake rate .................................................................................................33 2.5.5.12 Assimilation efficiency ..............................................................................................33 2.5.5.13 Decision rules.............................................................................................................33 2.5.6 Modelling habitat loss...............................................................................................33 2.5.7 Summary of the parameterised model....................................................................35 3. MODEL PREDICTIONS OF THE EFFECT OF THE DEVELOPMENT ON PIED OYSTERCATCHER FORAGING CARRYING CAPACITY........................36 3.1 Quantity of Food in Relation to the Requirements of the Birds........................................36 3.2 Predicted Behaviour, Body Mass and Survival in the Absence of Habitat Loss..............39 3.2.1 Patch choice...............................................................................................................39 3.2.2 Diet selection..............................................................................................................39 3.2.3 Food intake rate ........................................................................................................40 3.2.4 Percentage of time spent feeding .............................................................................40 3.2.5 Body mass and survival............................................................................................40 3.3 Predicted Effect of Partial Habitat Loss on Behaviour, Body Mass and Survival...........42 3.3.1 Behaviour...................................................................................................................42