Cormorant population stable at 26,000 couples

About 25,760 cormorant nests were counted in Finnish coastal areas this summer, said the Finnish Environment Institute (SYKE) in a press release.

In the last five years, the nesting population has varied by only a few percentages. However, there is wide regional variation in the number of nests annually and the effect of hunting by the white-tailed eagle on nesting success and the locations of the colonies is increasing.

One-third of the cormorant nests were found in both the Gulf of Finland and the Bothnian Sea, one-fifth in the Archipelago Sea, 12% in Kvarken and 5% in the Bothnian Bay.

In Kvarken, the population declined by 16%, in the Archipelago Sea by 14%, and in the Gulf of Finland by two per cent year on year, while it increased by 70% in the Bothnian Bay and by 17% in the Bothnian Sea.

All in all, the cormorant population in the Gulf of Bothnia increased by 10% to about 12,200 nests, with 7,660 located in the Bothnian Sea, 3,200 in Kvarken, and 1,360 in the Bothnian Bay. In the Gulf of Finland, the population comprised approximately 8,500 nests and in the Archipelago Sea, 5,000 nests.

The largest communities are seen between Porvoo and Mustasaari.

Fifty-four cormorant colonies were observed in Finland on 83 islets or islands over an area of 81 hectares. More than half of the entire population nested in the eight largest colonies.

Colonies of more than one thousand nests were located in Rauma (3,600 nests), Mustasaari (1,560), Turku (1,540), Uusikaupunki (1,540), Porvoo (1,320), Pori (1,320), Kirkkonummi (1,300), and Eurajoki (1,170). The strongest increase at the municipal level was observed in Rauma and Kokkola, while in Nykarleby, the number of nests declined by more than a half.

More than 400 cormorant nests with eggs were found to have been illegally destroyed on three treeless islets in Pyhtää and Hamina. As a result, new nests were built on forested islets in the inner archipelago, closer to areas with summer houses.

Hunting by the white-tailed eagle continued to increase, weakening the fledgling production even in large nesting colonies. As a result, the number of adult cormorants returning to their area of birth is relatively lower.

Hunting by the white-tailed eagle also affects the locations of the colonies and their way of nesting: nesting is increasingly concentrated in the inner archipelago and the proportion of nesting in forests is growing.