Eskildsen, J. 2006. Research Notes from NERI, No. 233. 50 p.
In 2006, the total number of cormorant nests counted in <st1:country-region w:st="on"><st1:place w:st="on">Denmark</st1:place></st1:country-region> was 37,404 distributed among 61 colonies. This number of nests corresponds to a 6% decline compared with 2005 and a 5% decline in relation to numbers breeding during the preceding 10 years. The number of colonies was 61 in 2006; i.e. the same level as in 2004. There were different trends among the regions in the development in nest numbers. The number of cormorant nests increased by 5% in southeast <st1:country-region w:st="on">Denmark</st1:country-region> , while there was a decrease of 10% in other parts of <st1:country-region w:st="on"><st1:place w:st="on">Denmark</st1:place></st1:country-region> .
The numbers of cormorant nests in West Jutland have now been decreasing for two years and there might be a connection to the intense regulation of cormorant nests that have taken place for some years in <st1:place w:st="on">West Jutland</st1:place> . However, the decrease in the number of cormorant nests in the southern part of Kattegat, where no regulation takes place, was as extensive in 2006 as in <st1:place w:st="on">West Jutland</st1:place> . The different developments among regions are probably to a large extent due to differences in the availability of fish.
More than 6,600 cormorant nests in 24 colonies were destroyed in 2006 corresponding to 18% of the total number of nests. The number of destroyed nests was 1,600 nests higher than in 2005. More than 75% of the control measures were made in colonies in <st1:place w:st="on">West Jutland</st1:place> and around Læsø. In 90% of the destroyed nests were sprayed with a fluid that seals the gas-permeable pores in the eggshells and consequently kills the embryo.
The most dramatic attempt to colonize a new area happened at Saltholm near <st1:City w:st="on"><st1:place w:st="on">Copenhagen</st1:place></st1:City> . In late spring a large number of cormorants suddenly began to build nests and a colony of 700 nests was established within few weeks. Probably these new settlers were cormorants from the colony at Eskilstorps near Falsterbo in southern <st1:country-region w:st="on"><st1:place w:st="on">Sweden</st1:place></st1:country-region> , where the cormorants had been driven away by humans shortly before.
There were very few early broods in 2006 compared with earlier years probably because of the late and very cold spring. It is unknown to what extent the cold spring was among the reasons for the general decline in the number of cormorant nests in 2006.
Full report in pdf format (960 kB).
