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No. 63: Denmark's breeding population of cormorants in 2015

Bregnballe. T. & Nitschke, M. 2015. Danmarks ynglebestand af skarver 2015. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 34 s. - Teknisk rapport fra DCE - Nationalt Center for Miljø og Energi nr. 63. dce2.au.dk/pub/TR63.pdf

Summary

This report presents the results of the annual count of apparently occupied Great Cormorant nests in Denmark. In 2015 a total of 31,076 nests were recorded in Denmark. The years 1993-2006 were characterised by a stable breeding population around 39,000 nests, whereafter numbers fell to around 26,400 nests in 2010-2013 (Fig. 1). Breeding numbers increased with 5,900 nests in 2014 and with 468 nests in 2015, i.e. an increase of 2 % from 2014 to 2015.

In two out of seven regions a decrease in breeding numbers from 2014 to 2015 was recorded, whereas numbers increased in the remaining five regions. A decrease of 15 % took place in the southwestern part of Kattegat and a decrease of 17 % was observed in the archipelago south of Funen. The proportional increase was small or modest in most regions but an increase of 48 % (634 nests) took place in the westernmost region including the fjords of western Jutland where the vast majority of breeders are found in Ringkøbing Fjord. A less pronounced increase of 15 % was seen in Limfjorden.

There were 73 breeding colonies in 2015, i.e. fewer than in 2014 when 78 sites had breeding cormorants. Three of the colonies in 2015 were established at localities which had not had breeding cormorants in former years. Earlier years’ trend of a gradual decrease in size of the largest colonies did not continue in 2015. The largest colony in 2015 was Stavns Fjord on the island of Samsø in the southwestern part of Kattegat. This colony held 2,004 nests.

The Danish Nature Agency, Ministry of the Environment conducted management to curtail the number of breeding cormorants in 10 colonies in 2015, and gave permission to private landowners to conduct management in another two colonies. In 2015 a total of 2,757 nests were exposed to management. The eggs in 2,422 of the nests were sprayed with vegetable oil and the remaining nests were removed. The number of nests exposed to management in 2015 was at the same level as in the years 2010-2012, i.e. higher than in 2013-2014 but far lower than in the years 2003-2009 when more than 4,000 nests were exposed to management annually.