Satellite tracking of the migratory pathways of first-year Lesser Black-backed Gulls Larus fuscus departing from the breeding grounds of different subspecies

The migratory behaviour of two Lesser Black-backed Gull Larus fuscus subspecies, fuscus and intermedius, was studied using satellite telemetry. To this end, first-year birds were equipped with satellite transmitters and released either at their natal site, or after transferring to a breeding site of the other subspecies. In addition, first-year birds from cross-breeding experiments between the two subspecies (fuscus x intermedius) were also equipped with satellite transmitters. In total, eleven first-year birds were successfully tracked during their initial autumn migration, at least one from each study group. First-year birds from the Danish intermedius subspecies migrated either southwest along the coast of the North Sea or through central Europe to Algeria. By contrast, first-year birds from the Finnish fuscus subspecies migrated on a south-southeastern course towards Ukraine and the Bosporus, Turkey. Only one of the transferred gulls could be tracked long enough to accurately determine the migratory behaviour: this bird from the intermedius subspecies left Finland on a south-southeasterly course towards the Ukraine, where transmission ceased. Thus, this gull resembled the migratory behaviour of the fuscus subspecies. One bird from the cross-breeding experiments wintered in Libya, but the migratory behaviour remained unknown due to the lack of positional data.