Ardea
Official journal of the Netherlands Ornithologists' Union

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Debout G., Rov N. & Sellers R.M. (1995) Status and population development of Cormorants Phalacrocorax carbo carbo breeding on the Atlantic coast of Europe. ARDEA 83 (1): 47-59
About 37 000 pairs of Cormorants currently breed on the North Atlantic coasts of western Europe (France, Britain, Ireland and Norway) representing about 83% of the world population of the nominate form of the species. Colonies typically number 10-500 pairs, with a maximum of 1400 pairs and, with one or two exceptions, occur almost wherever there is suitable habitat. The preferred breeding sites are cliffs, stacks and rocky offshore islands though some, notably in Ireland, breed in trees. Amongst the factors which determine colony size the extent of suitable feeding areas (water less than 10 m deep) within 30 km of the colony and the proximity of other colonies are shown to be particularly important. The general trend in population numbers in the past 10-20 years has been upward, probably as a result of increased protection both through legislation and by the establishment of safe havens such as nature reserves. Rates of increase vary somewhat from area to area but have typically averaged a few percent per annum. The only area where declines continue is northern Scotland. Two cases of sudden decreases in breeding numbers are described (in Norway in 1985-87 and in SW Wales in 1991). Both appear to have been due to periods of adverse weather at the pre-breeding or early breeding stages acting to keep fish stocks in deeper water where Cormorants could not catch them, perhaps coupled in the former case by reductions in fish stocks.


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