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Extensive post-breeding movements of the Adriatic Yellow-legged Gulls Larus michahellis

Yellow-legged Gull Larus michahellis is generally considered to be sedentary and dispersive, with long-distance dispersal of young birds developed after 1970s. In this paper we present the analysis of the movement of the Yellow-legged Gulls from the eastern Adriatic coast based on observation of colour-ringed birds marked between 1999 and 2011. A total of 4234 sightings of 1666 Yellow-legged Gulls marked as chicks were analysed. Our results showed a clear preference in the direction of the movement of Yellow-legged Gulls and the significant differences in the directions of movements and longitude of the observation sites of birds from different colonies. During summer and autumn majority of gulls moved towards north, to the Baltic and North Sea coasts. Maximum distances covered (1958 km for juvenile and 1380 km for adult birds) were much greater than for the other studied populations of the Yellow-legged Gull. We found no difference between directions of the movement among age classes, while distances decreased with age. Three important features: long-distance movements, migratoriness of adults and differences in movements between colonies, disprove the theory that post-breeding movements of the Yellow-legged Gull is recently developed as the result of the population increase. We presume that recent pattern of movement reflects the evolutionary history of the Yellow-legged Gulls and might be inherited or resulting from the experience and transferred by learning between generations among birds from the same colony.

Yellow-legged Gull Larus michahellis; Long-distance movements; Adriatic Sea

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