Habitat-mediated population limitation in a colonial central-place forager : the sky is not the limit for the black-browed albatross
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Animal populations are frequently limited by the availability of food or of habitat. In central-place foragers, the cost of accessing these resources is distance-dependent rather than uniform in space. However, in seabirds, a widely studied exemplar of this paradigm, empirical population models have hitherto ignored this cost. In part, this is because non-independence among colonies makes it difficult to define population units. Here, we model the effects of both resource availability and accessibility on populations of a wide-ranging, pelagic seabird, the black-browed albatross Thalassarche melanophris. Adopting a multi-scale approach, we define regional populations objectively as spatial clusters of colonies. We consider two readily quantifiable proxies of resource availability: the extent of neritic waters (the preferred foraging habitat) and net primary production (NPP). We show that the size of regional albatross populations has a strong dependence, after weighting for accessibility, on habitat availability and to a lesser extent, NPP. Our results provide indirect support for the hypothesis that seabird populations are regulated from the bottom-up by food availability during the breeding season, and also suggest that the spatio-temporal predictability of food may be limiting. Moreover, we demonstrate a straightforward, widely applicable method for estimating resource limitation in populations of central-place foragers.
Wakefield , E D , Phillips , R A & Mattiopoulos , J 2014 , ' Habitat-mediated population limitation in a colonial central-place forager : the sky is not the limit for the black-browed albatross ' Proceedings of the Royal Society B: Biological Sciences , vol 281 , no. 1778 , 20132883 . DOI: 10.1098/rspb.2013.2883
Proceedings of the Royal Society B: Biological Sciences
© 2014 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0/, which permits unrestricted use, provided the original author and source are credited.
This work was supported by the UK Natural Environment Research Council (NER/S/A/2005/13648).
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