Researchers have used GPS trackers to reveal how juvenile Whimbrel undertake their first migration to West Africa.
Iceland hosts a high percentage of the world's breeding Whimbrel, with a 2016 estimate putting the number of breeding pairs in the country at 256,000.
Juvenile Whimbrel fly non-stop across the Atlantic to West Africa, but their flight paths are less direct than those of adults (Alex Penn).
Research over the last few years has revealed that adult birds routinely undertake a non-stop journey over the ocean between Iceland and the coast of West Africa in the autumn, a distance of up to 6,000 km. Spring migration can be undertaken with a similiar non-stop flight, but the birds usually rest for a week or two in a stopover area before completing the migration.
There were still many unknowns about the migration of juvenile Whimbrel, so scientists fitted GPS trackers to 13 young birds in 2021 and 2022. The devices provided location updates every six hours, revealing a detailed picture of the journeys that 11 of the birds undertook.
The data revealed that juveniles make the same long-distance flight to Africa. However, they set off on their migration later (15 days on average) and follow a less direct path. Young birds also tended to make stops once they reached the West African coast but before reaching their wintering site, while adults usually headed straight for their final destination, resulting in a slower overall travel speed for juveniles.
The researchers said that Whimbrel presents an 'exceptional' opportunity to study the individual development of migration, as earlier juveniles may be able to learn from adults in mixed-age flocks of migrants, while late departing juveniles are unlikely to benefit from the experience of older birds. Simultaneous tracking of adults and juveniles may reveal the role of social learning in young birds' first migration.
Carneiro, C Gunnarsson, T G, Kaasiku, T, Piersma, T, and Alves, J A, 2023. Icelandic Whimbrel first migration: Non‐stop until West Africa, yet later departure and slower travel than adults. Ibis. DOI: https://doi.org/10.1111/ibi.13282