Culling project on herring gulls of the central Gulf of Finland 2004–2007

Between 2004 and 2007, 15 000 herring gulls and 600 greater black-backed gulls were culled at four large open-plan refuse tips in the Uusimaa province. The cull was planned and executed as a joint effort by several agencies representing nature conservation, animal protection, communal administration, game management, game research etc. The aim was to implement management measures to minimize nuisance effects in towns by large gull populations, and to reduce the predation rate on chicks of the lesser black-backed gull, a species considered endangered in the Baltic Sea.

As a result of the culling, the herring gull population was reduced by 34% and the greater black-backed gull population by 25% in the central Gulf of Finland. Based on ringing recovery analysis, the cull largely targeted birds within 100 kilometres of the coastline and to a lesser extent gulls from inland areas. The bulk of the gulls originated from the eight core municipalities surrounding the region where the culls were conducted.

During the project, the predation rate by the herring gull on the chicks of the lesser blackbacked gull was reduced to about one-quarter of the 1990s level. It is suggested that this reduction is caused by the cull, reducing the numbers of predatory gulls along the coast. The project provided evidence that extra mortality in adult population leads to an excessive population decline, but these changes may not be long-lasting after culling is ceased. This is due to density-dependent effects that tend to compensate for the prompt increase in adult mortality induced by culling.