首页 | 本学科首页   官方微博 | 高级检索  
   检索      


Intake rates and the functional response in shorebirds (Charadriiformes) eating macro-invertebrates
Authors:Goss-Custard John D  West Andrew D  Yates Michael G  Caldow Richard W G  Stillman Richard A  Bardsley Louise  Castilla Juan  Castro Macarena  Dierschke Volker  Durell Sarah E A Le V Dit  Eichhorn Goetz  Ens Bruno J  Exo Klaus-Michael  Udayangani-Fernando P U  Ferns Peter N  Hockey Philip A R  Gill Jennifer A  Johnstone Ian  Kalejta-Summers Bozena  Masero Jose A  Moreira Francisco  Nagarajan Rajarathina Velu  Owens Ian P F  Pacheco Cristian  Perez-Hurtado Alejandro  Rogers Danny  Scheiffarth Gregor  Sitters Humphrey  Sutherland William J  Triplet Patrick  Worrall Dave H  Zharikov Yuri  Zwarts Leo  Pettifor Richard A
Institution:Centre for Ecology and Hydrology, Winfrith Technology Centre, Dorchester DT2 8ZD, UK;Departamento de Ecologia, Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Codigo Postal: 6513677, Santiago, Chile;Departamento de Biologia, Facultad de Ciencias del Mar y Ambientals, E-11510 Puerto Real, Spain;Research and Technology Centre, University of Kiel, Hafentörn, D-25671 Büsum, Germany;Zoological Laboratory, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands;Alterra, P.O. Box 167, NL-1790 AD Den Burg (Texel), The Netherlands;Institut für Vogelforschung "Vogelwarte Helgoland", An der Vogelwarte 21, D-26386 Wilhelmshaven, Germany;29 Askam Road, Bramley, Rotherham, South Yorkshire S66 3YR, UK;School of Biosciences, Cardiff University, Cardiff CF 10 3TL, UK;DST/NRF Centre of Excellence at the Percy FitzPatrick Institute of African Ornithology, University of Cape Town, Rondebosch 7701, South Africa;Schools of Biological and Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK;RSPB North Wales Office, Maes y Ffynnon, Penrhosgarnedd, Bangor LL57 2DW, UK;7 Mill Crescent, N. Kessock, Inverness IV1 3XY, UK;Centro de Ecologia Aplicada 'Prof. Baeta Neves', Instituto Superior de Agraonomia, Tapada da Ajuda, 1349-017 Lisboa, Portugal;Department of Psychology, University of Exeter, Exeter EX4 4QG, UK;Department of Biological Sciences, and NERC Centre for Population Biology, Imperial College London, Silwood Park, Ascot, Berkshire SL5 7PY, UK;Johnstone Centre, Charles Stuart University, PO Box 789, Albury NSW 2640, Australia;Limosa, Old Ebford Lane, Ebford, Exeter EX3 0QR, UK;SMACOPI, 1 place de l'Amiral Courbet, 80 100 Abbeville, France;Countryside Council for Wales, Haverfordwest, Pembrokeshire SA67 8TB, UK;SOLS, University of Queensland, Brisbane, QLD 4072, Australia;RIZA, P.O. Box 17, Lelystad, The Netherlands;Institute of Zoology, Zoological Society of London, Regents Park, London NW1 4RY, UK
Abstract:As field determinations take much effort, it would be useful to be able to predict easily the coefficients describing the functional response of free-living predators, the function relating food intake rate to the abundance of food organisms in the environment. As a means easily to parameterise an individual-based model of shorebird Charadriiformes populations, we attempted this for shorebirds eating macro-invertebrates. Intake rate is measured as the ash-free dry mass (AFDM) per second of active foraging; i.e. excluding time spent on digestive pauses and other activities, such as preening. The present and previous studies show that the general shape of the functional response in shorebirds eating approximately the same size of prey across the full range of prey density is a decelerating rise to a plateau, thus approximating the Holling type II ('disc equation') formulation. But field studies confirmed that the asymptote was not set by handling time, as assumed by the disc equation, because only about half the foraging time was spent in successfully or unsuccessfully attacking and handling prey, the rest being devoted to searching.A review of 30 functional responses showed that intake rate in free-living shorebirds varied independently of prey density over a wide range, with the asymptote being reached at very low prey densities (<150/m-2). Accordingly, most of the many studies of shorebird intake rate have probably been conducted at or near the asymptote of the functional response, suggesting that equations that predict intake rate should also predict the asymptote.A multivariate analysis of 468 'spot' estimates of intake rates from 26 shorebirds identified ten variables, representing prey and shorebird characteristics, that accounted for 81% of the variance in logarithm-transformed intake rate. But four-variables accounted for almost as much (77.3%), these being bird size, prey size, whether the bird was an oystercatcher Haematopus ostralegus eating mussels Mytilus edulis, or breeding. The four variable equation under-predicted, on average, the observed 30 estimates of the asymptote by 11.6%, but this discrepancy was reduced to 0.2% when two suspect estimates from one early study in the 1960s were removed. The equation therefore predicted the observed asymptote very successfully in 93% of cases. We conclude that the asymptote can be reliably predicted from just four easily measured variables. Indeed, if the birds are not breeding and are not oystercatchers eating mussels, reliable predictions can be obtained using just two variables, bird and prey sizes. A multivariate analysis of 23 estimates of the half-asymptote constant suggested they were smaller when prey were small but greater when the birds were large, especially in oystercatchers. The resulting equation could be used to predict the half-asymptote constant, but its predictive power has yet to be tested. As well as predicting the asymptote of the functional response, the equations will enable research workers engaged in many areas of shorebird ecology and behaviour to estimate intake rate without the need for conventional time-consuming field studies, including species for which it has not yet proved possible to measure intake rate in the field.
Keywords:Charadriiformes  foraging behaviour  functional response  individual-based models  intake rate  predator-prey interactions  shorebirds
本文献已被 PubMed 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号