Aarhus University Seal / Aarhus Universitets segl

No. 41: Danish breeding population of cormorants in 2014

Bregnballe, T. & Therkildsen, O.R. 2014. Danmarks ynglebestand af skarver i 2014. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 24 s. - Teknisk rapport fra DCE - Nationalt Center for Miljø og Energi nr. 41. dce2.au.dk/pub/TR41.pdf

Summary

This report presents the results of counts of Great Cormorant Phalacrocorax carbo sinensis nests in breeding colonies in Denmark in the spring of 2014. Great Cormorants were breeding at 76 different localities with a total of 30,503 breeding pairs (nests) in Denmark in 2014. This is an increase of five colonies and 5,801 nests (23%) since 2013. Breeding numbers in 2014 were higher than in the previous four years when numbers ranged between 24,702 and 28,037 breeding pairs. It is suggested that the increase in 2014 was due to an increase in the proportion of potential breeders attempting to breed, combined with high breeding success in several Danish breeding colonies 2-3 years earlier, leading to higher recruitment of young birds. Breeding conditions were apparently extraordinarily good in Denmark in 2014 due to the mild winter and the early spring combined with high availability of fish within the feeding range of many of the colonies (partly judged from successful production of large broods).

The number of breeding pairs increased in all seven regions in Denmark. The largest increases were recorded in Smålandsfarvandet, the southwestern area of Kattegat and in the northern parts of Zealand (increases of 1,180-1,580 nests recorded from 2013 to 2014). Seven out of the 76 breeding colonies were new colonies founded at localities where no cormorants had been breeding in previous years. Breeding attempts were also recorded at four localities where no cormorants had nested for 3-12 years prior to 2014. The largest colony had 2,414 nests (located in Stavns Fjord on Samsø) and the second largest colony had 1,844 nests (Brændegård Sø-Nørresø on South Funen).

The Danish Nature Agency carried out management actions in five breeding colonies with the effect that no chicks fledged from 1,723 nests. The actions involved oiling of eggs (1,224 nests in three colonies), removal of eggs (174 nests in one colony) and removal of chicks (325 nests in one new colony). The removal of chicks was necessary at one new colony as it was located close to Copenhagen Airport and the colony was not discovered until late in the breeding season, otherwise oiling of eggs would have been carried out. Overall the management actions affected a smaller number of nests in 2014 than in previous years, e.g. management actions affected 2,600-7,200 nests annually during 2001-2012.