Abudance and seasonal migration of gulls (laridae) on the Lithuanian Baltic sea coast

Abstract

On the basis of long-term visual observations carried out according to E. Kumari’s methodology in 1974-2006 at the sea coast of Palanga, an analysis of spring migration of nine species of gulls has been done. The main migratory characteristics, seasonal and annual dynamics, phenology and dependence of migration intensity on weather variables are reported. During observations were registered nine species of gulls. The Little Gull (Larus minutus), Black – headed Gull (Larus ridibundus), Common Gull (Larus canus), Lesser Black – backed Gull (Larus fuscus), Herring Gull (Larus argentatus) and Great Black – backed Gull (Larus marinus) were abundant and the Kittiwake (Rissa tridactyla), Yellow – legged Gull (Larus cachinnans) and Glaucous Gull (Larus hyperboreus) were uncommon. Numbers of black – headed gulls, common gulls, lesser black – backed gulls and great black – backed gulls were on the statistical decrease. On the average, spring migration of the Little Gull was started on the 12th of April and other species of gulls – on the 12 – 17th of March. The duration of the Common Gull migration was the longest (on the average 67 days) and the Little Gull migrated the most shortly (on the average 29 days). Gulls abundantly migrated from the fifth 5 - day period in March to the third 5 - day period in May. The majority of gulls migrated in the flocks of 1 - 5 individuals. The most of them moved northward at 1 – 20 m altitude during the 2nd, 3rd and 4th hours after sunrise. The intensity of migration was depended on 8 meteorological factors for northward and 6 factors influenced the migration for southward. The paper contains the main information about environmental and anthropogenic factors affecting abundance of gulls breeding in the Baltic Sea region which is regarded to be among the most polluted marine ecosystems of the world.