Cormorant population grew to 24,000 breeding pairs

Press release 2015-08-14 at 13:05
Merimetsoja
© Heikki Kotiranta
A total of approximately 24,000 cormorant nests were counted in Finland in summer 2015, an increase of 19% from the previous year. 75% of the numerical growth was focused on three already large colonies, which now account for over a third of Finland's nesting cormorant population.

Finland's largest cormorant populations were located in Merikarvia (4,120 nests), Uusikaupunki (2,670 nests) and Luvia (1,770 nests). Other colonies exceeding one thousand nests were located in Virolahti, Kirkkonummi and Rauma. Colonies were found in the areas of 31 municipalities or cities.

The strongest breeding cormorant population was found in the Gulf of Finland (8,470 nests). A total of 7,560 nests were counted in the Bothnian Sea, while 5,400 nests were counted in the Archipelago Sea, 2,250 in Kvarken and 315 in the Bay of Bothnia.

Just over half of the established colonies exhibited growth, while the rest either declined or remained the same size as the previous summer. The number of nests increased the most in Satakunta, where an increase of 2,000 nests was recorded. In the Gulf of Finland, the Archipelago Sea and Kvarken the increase was approximately 500 nests each, while in the Bay of Bothnia the population increased by 110 nests.

A total of 46 cormorant colonies were found in Finnish sea areas, located on 74 islets or islands over an area totalling approximately 57 hectares. One fifth of the cormorants nested in trees. Over half of the nests were located in nature conservation areas. Six new colonies were found, located in Pyhtää, Loviisa, Raasepori, Naantali, Mustasaari and Vaasa.

Total number of cormorant nests in Finland 2006-2015

Cormorant nests
 

Annual growth rate of the cormorant breeding population in Finland 2006-2015

Merimetsokannan prosentuaalinen kasvu vuosina 2006-2015
 

White-tailed eagles reduce nesting success and decrease the number of nests locally

Due to the presence of white-tailed eagles, cormorants no longer nested in the outer archipelago of Raasepori, while in Pargas the number of nests has declined to a third over the last four years. The number of nests also declined significantly in Kirkkonummi and Pori. A large number of white-tailed eagle sightings were recorded particularly in the cormorant colonies of Pargas, Uusikaupunki and Luvia. One colony in Pargas recorded 26 concurrent white-tailed eagle sightings, while a colony in Uusikaupunki recorded 17 concurrent sightings.

The nesting of a total of five colonies failed completely, while a further two colonies failed partially. The total number of destroyed nests found was nearly 1,400. Many of these were most likely caused by white-tailed eagles. Nests confirmed to have been illegally destroyed by humans were found at least in Luvia (394 nests).

Number of cormorant nests by sea areas in Finland 2006-2015

Cormorant nest numbers
 

Cormorant nesting colonies in Finland in the summer of 2015

Merimetsokoloniat kesällä 2015
 

Further information

Researcher Pekka Rusanen, Finnish Environment Institute SYKE,
tel. +358 400 148 691, firstname.lastname@ymparisto.fi

Senior Researcher Markku Mikkola-Roos, Finnish Environment Institute SYKE,
tel. +358 400 148 685, firstname.lastname@ymparisto.fi

Communications Manager Sirpa Pellinen, Finnish Environment Institute SYKE,
tel. +358 40 740 2754, firstname.lastname@ymparisto.fi