Habitat utilisation during staging affects body condition in a long distance migrant, Branta bernicla hrota: potential impacts on fitness?

Authors

  • R. Inger,

  • G. A. Gudmundsson,

  • G. D. Ruxton,

  • J. Newton,

  • K. Colhoun,

  • S. Auhage,

  • S. Bearhop


R. Inger (correspondance) and S. Bearhop, Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Cornwall Campus. Penryn, Cornwall TR10 9EZ. Email: richinger@gmail.com. – G. A. Gudmundsson, Icelandic Institute of Natural History, PO Box 5320, IS-125 Reykjavik, Iceland. – G. D. Ruxton, Division of Environmental and Evolutionary Biology, Institute of Biomedical & Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow, G12 8QQ, UK. – J. Newton, NERC Life Sciences Mass Spectrometry Facility, Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride, G75 0QF, UK. – K. Colhoun, Wildfowl and Wetlands Trust, Castle Espie Wetlands Centre, Ballydrain Road, Comber, County Down, BT23 6EA, UK. – S. Auhage, Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK.

Abstract

There is considerable evidence to suggest that an animal's ability to access the appropriate resources at one time of year may profoundly restrict its performance at another. For migrants, wintering and breeding periods are often connected by refuelling or staging periods, critical (particularly for females) in attaining the body reserves required to ensure successful breeding. However in many instances there are differences in the extent to which different individuals gain access to the highest quality resources. Here we demonstrate how body condition in brent geese Branta bernicla hrota, during spring staging is related to differences in marine and terrestrial habitat utilisation (inferred from stable isotope analysis). Female birds with high fat scores feed to a greater extent on marine resources. Body mass and condition are also higher in individuals utilising more marine resources. Given that body mass at spring staging is correlated with reproductive success, the extent of marine habitat maybe critical to this population. Combining this with data from previous studies of dark-bellied brent geese Branta bernicla bernicla, we predict the potential impacts of spring staging resource utilisation on future breeding success. Although staging is of short duration compared to the other components of annual cycles of migratory species, our results suggest that the quality of staging grounds may be vitally important to population processes.

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