Annual survival of Arctic terns in western Iceland

Many seabird species in the North Atlantic region have shown considerable declines in their populations during recent decades. One such species is the Arctic tern (Sterna paradisaea), a small seabird which migrates farther than any other seabird each year and whose global population is thought to be in decline. We used banding data of chicks and adults, spanning five decades (1974–2017) from a tern colony on Flatey, in western Iceland, to generate the first assessment of annual survival in this species in Iceland. Survival from just after hatching to the next summer was estimated to be 0.119 ± 0.024 (SE), while annual survival of adult birds (older than one year) was high at 0.952 ± 0.030. Although our data were insufficient to assess annual variation in adult survival, we noted a reduced survival (0.851 ± 0.034) in recent years (since 2000), coincident with a collapse in local sand lance populations. Reduced adult survival, along with other factors, is likely contributing to declining populations of this iconic species in Iceland, a country supporting 20–30% of the world’s breeding population.