High variability in the migratory behaviour of a tropical seabird.

We investigated the non-breeding movements and distribution of West African Crested terns (Thalasseus albididorsalis) breeding in one of the largest colonies of the species, in Guinea-Bissau. Through GPS tracking of six individuals, we show that half of the birds performed long-distance migrations to non-breeding sites located up to 5039 km south of the colony, mostly in Nigeria and Angola. The other half performed short-distance migrations to areas within 340 km of the breeding colony, mainly in Guinea. These results show high variability on the migratory strategies of the West African Crested Tern and suggest low migratory connectivity within the studied population. Regardless of their migratory strategy, all tracked birds visited at least one additional breeding colony both after and before the breeding season. This behaviour might be particularly relevant for species breeding in unstable environments, which is the case of the studied species, nesting in highly dynamic coastal sandbanks. During the non-breeding season West African Crested terns used coastal areas falling within 18 different jurisdictions, highlighting the need for concerted action between all coastal countries of Western Africa, from Senegal to Angola, for the conservation of this species. [ABSTRACT FROM AUTHOR]