Nuvarande status och populationsdynamik för nominatrasen av silltrut Larus fuscus fuscus i Vita havet

Abstract

The size of the colonies of the nominate subspecies of Lesser Black-backed Gull Larus fuscus fuscus was monitored annually in Onega Bay of the White Sea in 1989—2006. The total current population in the studied area is about 2,100 pairs or 10% of the world population of this subspecies. During the time of monitoring the population increased more than three times, and since the 1960s it has increased more than six times. The main increase was observed in the seven biggest colonies (more than 100 pairs) where more than 60% of the White Sea population was breeding. Average long-term clutch size was 2.44, and breeding success was 1.0 fledgelings per pair. The increase in number probably results from the decrease of disturbance in the breeding area and improvement of feeding resources. The increase of the White Sea population contrasts with a strong decline of the Baltic population.