Individual specialization in resource use is a widespread driver for intra-population trait variation, playing a crucial evolutionary role in free-living animals. We investigated the individual foraging specialization of Black-tailed Godwits ( Limosa limosa islandica) during the wintering period. Godwits displayed distinct degrees of individual specialization in diet and microhabitat use, indicating the presence of both generalist and specialist birds. Females were overall more specialist than males, primarily consuming polychaetes. Specialist males consumed mainly bivalves, but some individuals also specialized on gastropods or polychaetes. Sexual dimorphism in bill length is probably important in determining the differences in specialization, as longer-billed individuals have access to deep-buried polychaetes inaccessible to most males. Different levels of specialization within the same sex, unrelated to bill length, were also found, suggesting that mechanisms other traits are involved in explaining individual specialization. Godwits specialized on bivalves achieved higher intake rates than non-specialist birds, supporting the idea that individual foraging choices or skills result in different short-term payoffs within the same population. Understanding whether short-term payoffs are good indicators of long-term fitness and how selection operates to favour the prevalence of specialist or generalist godwits is a major future challenge.
Bibliographical noteFunding Information:
We are grateful to Baía do Tejo S.A. and Arq. Luís Lima for giving permission to access the area of Siderurgia Nacional. Pete Potts, Ruth Croger and many other members and volunteers of the Farlington Ringing Group, provided an invaluable contribution in marking godwits in the Tagus estuary in the last few years. The manuscript beneficiated from the comments of two anonymous referees. This study was supported by Fundação para a Ciência e Tecnologia (FCT) , through Projects “Invisible Links” (PTDC/MAR/119920/2010) and PEst-C/MAR/LA0017/2013, European Funds through COMPETE and NERC (JAA, JAG). TC beneficiated of a post-doctoral grant from FCT ( SFRH/BPD/46967/2008 ). Part of this work was carried out while JPG was under a research contract within project “Sustainable Use of Marine Resources – MARES” (CENTRO-07-ST24-FEDER-002033), co-financed by “Mais Centro” Regional Operational Programme (Centro Region) and European Regional Development Fund (ERDF).
- Black-tailed Godwit
- Foraging ecology
- Individual specialization
- Short-term payoffs