Migration Patterns of Adult and Juvenile Lesser Black-Backed GullsLarus fuscusfrom Northern Norway

Abstract

To explore migration patterns of Lesser Black-backed Gulls Larus fuscus breeding in northern Norway, this study presents resightings of 16 adult and 83 juvenile birds marked in this region. Adults of the endangered nominate sub-species L. f. fuscus had a low probability of being observed (only 3.5% of marked birds were observed), probably because the adults winter in areas with few observers, such as eastern and central Africa. In contrast, birds of the greyish-mantled subspecies L. f. intermedius or L. f. graellsii had a high probability of being observed (45.5%). Adults of intermedius/graellsii had a western migration route and wintered mainly in western Europe and northwest Africa, Adults exhibited a high site fidelity to wintering areas. Birds marked as juveniles had two different migration routes. (1) 30% of the observed birds crossed the Scandinavian Peninsula to Finland and the Baltic countries, and then migrated to the eastern Mediterranean (Israel and Egypt) down to eastern and central Africa (Kenya and Cameroon). (2) The other 70% followed the European coast and overwintered in UK, the Iberian Peninsula, Morocco, Mauritania and Senegal. There were no indications that juvenile migration patterns differed among subspecies as juveniles from mixed and pure fuscus colonies exhibited similar patterns. The apparent differences in migration patterns between adult and juvenile fuscus may be a result of juvenile exploratory migration.