Mortality in migratory birds - where and when?

Marsh harrier with satellite tag. Photo: Roine Strandberg

A new study on raptor migration, published in the January issue of Journal of Animal Ecology, reveals direct evidence about when and where migrants die. 
By identifying cases of confirmed and probable deaths in three species of long-distance migratory raptors tracked by satellite telemetry, the authors (Raymond Klaassen et al) showed that mortality rate was about six times higher during migration season than during stationary periods. They also found that spring mortality occurred mainly in Africa, while most mortality during autumn took place in Europe.