The sky is not the limit for the Black-browed Albatross: limited by food availability

Ewan Wakefield (British Antarctic Survey, Cambridge, UK) and colleagues write in the journal Proceedings of the Royal Society B on what regulates populations of Black-browed Albatrosses Thalassarche melanophris.

The paper’s abstract follows:

“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.”

Black-browed Albatross in flight, photograph by Juan Pablo Seco Pon

With thanks to Richard Phillips for information.

Reference:

Wakefield, E.D., Phillips, R.A. & Matthiopoulos, 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.

John Cooper, ACAP Information Officer, 22 January 2014