Distribution and foraging interactions of seabirds and marine mammals in the North Sea: a metapopulation analysis

The top-predator community off the British east coast consists of 50 species of seabirds and marine mammals, most of which are piscivorous. Sandeels are important prey for many species, but reduced sandeel abundance has had detectable consequences on breeding success for few, mostly surface feeding seabirds. Breeding success and population trends differ between species, suggesting species-specific responses on fluctuating prey stocks. The IMPRESS project aimed at a detailed evaluation of prey availability issues, believed to enhance sandeel intake rates of four common seabirds with contrasting foraging techniques and area usage in the Wee Bankie area, using a combination of advanced technology and field observations. To put these observations into perspective, a metapopulation study of top-predator distribution patterns and at-sea foraging interactions was conducted in the NW North Sea. With numerous predators utilising the same prey or a similar resource, issues as facilitation, interference and exploitation competition, and kleptoparasitism have to be considered. Four target species were studied in the Wee Bankie area, but more predators seemingly interact and none were excluded beforehand in the metapopulation study. It was found that Black-legged Kittiwakes and Common Guillemots utilise d a zone of variable width up to 80 or 100km away from the coast. Kittiwakes relied substantially on prey facilitation by auks an