Post-breeding migration of four Long-tailed Skuas (Stercorarius longicaudus) from North and East Greenland to West Africa

The Long-tailed Skua (Stercorarius longicaudus) is a specialist predator of lemmings during the summer and hence an important component of the tundra ecosystems, but most of its life cycle takes place offshore and remains largely unknown outside of the breeding season. Using 9.5-g solar-powered satellite transmitters, we were able to document for the first time the post-breeding movements of the Long-tailed Skua, from its high-Arctic breeding-grounds in North and Eastern Greenland to the tropical waters of West Africa. The birds traveled the approximately 10,000 km of this migration in only 3-5 weeks, covering 800-900 km/day during active migration, which also occurred during nighttime. Leaving their breeding areas in August (except for one failed breeder), the Long-tailed Skuas first moved south along the coast of East Greenland towards a staging area off the Canadian Great Banks where they stayed for 1-3 weeks. From there, they crossed the Atlantic Ocean eastwards in just 1 week, entering African waters near the Madeira Archipelago in September. Although only four birds were monitored for 1.5-3 months, the data reveal that the migration routes between birds breeding in different locations and in different years were relatively similar.