Foraging strategies of seabird species can vary between and within individuals. A new study shows that great skua breeding on Bjørnøya have high individual foraging specialization: they forage regularly in a nearby seabird colony, out at sea and some do both.

There are many different foraging strategies of seabirds, and these are influenced by a multitude of factors including: age, sex, reproductive status, individual specialization and environmental conditions. Within a single breeding season, foraging strategies may alter throughout the season, e.g. to satisfy different energy and time demands or as a response to changes in prey availability. Individual specialization may be an expression of fidelity to feeding areas, at-sea activity and specific prey items. In this study, the researchers looked at foraging strategies of great skua Stercorarius skua at Bjørnøya. The colony on Bjørnøya is one of the northernmost breeding sites of great skuas and it harbours the largest breeding population in the Barents Sea region. The great skua is a dietary generalist exploiting a large variety of prey. They are known to catch small fish close to the sea surface, steal food from other seabirds (kleptoparasitism), prey on other birds, their eggs and chicks and feed on discards from fishing vessels. The researchers used GPS-loggers to investigate which factors may affect maximal range from the colony, total distance covered and total duration of foraging trips, and through that determine different individual foraging behavior.

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The study showed that individual specialization had the largest effect on foraging trips of great skua breeding on Bjørnøya. They identified three main strategies: foraging on other seabirds, foraging at sea and a generalist strategy mixing the two. The majority of the great skua tracked through the breeding season foraged out at sea likely catching fish, foraging on discards from fishing vessel and/or kleptoparasiting other seabirds.

Contact person: Hallvard Strøm, Norwegian Polar Institute

Great skua with GPS-logger attacted.
Photo: Hálfdán Helgi Helgason