Annual and between-colony variation in productivity of Arctic Terns in West Iceland

Abstract

Capsule Recent annual productivity of Arctic Terns Sterna paradisaea in Iceland has been persistently low, primarily because of very low rates of chick fledging. Aims To quantify current levels of productivity in Arctic Terns in Iceland, and the extent to which this varies among 10 colonies across the Snaefellsnes peninsula, West Iceland. Methods Between 2008 and 2011, up to 10 Arctic Tern colonies were monitored annually and a total of 635 nests were monitored from laying to fledging or failure. Results Arctic Tern productivity in colonies across the peninsula varied little between years; the clutch size of 635 nests did not vary significantly between colonies or years, and hatching success was consistently high (80–100%). However, fledging success was low in all years, although with some variation between colonies. Conclusion Population declines are evident among Arctic Terns and many other seabird populations around the North Atlantic, but little is known about the status of the huge populations breeding in Iceland. The low productivity across the colonies and years suggests that environmental changes are also impacting Arctic Tern populations in Iceland. We discuss the potential causes of these demographic patterns and the implications for the conservation of this species in Iceland.