title: Habitat-mediated population limitation in a colonial central-place forager: the sky is not the limit for the black-browed albatross.
abstract: 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.
authors.affiliation: British Antarctic Survey, Natural Environment Research Council, , High Cross, Madingley Road, Cambridge CB3 0ET, UK, Scottish Oceans Institute, School of Biology, University of St Andrews, , Fife KY16 8LB, UK, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, , Glasgow G12 8QQ, UK.
authors.forename: Ewan D
authors.initials: ED
authors.lastname: Wakefield
authors.forename: Richard A
authors.initials: RA
authors.lastname: Phillips
authors.forename: Jason
authors.initials: J
authors.lastname: Matthiopoulos
mesh_terms: D000818:Animals; D001717:Birds / Q000502:physiology*; D017753:Ecosystem; D005247:Feeding Behavior; D011156:Population Density; D011157:Population Dynamics
keywords: density dependence; habitat preference; net primary production; population regulation; seabirds; spatial segregation