BIOLOGICAL DIVERSITY IN ICELAND - Convention on Biological ...

found quite widely in therocky and mountainousparts of the country. Thehuge white-tailed eagle(Haliaeetus albicilla) wasformerly fairly common.The population has beenreduced to such an extent,through persecution andindirect poisoning forfoxes, that grave concernhas been expressed for itsFigure 6. Approximately 20-40% of the North Atlanticpopulation of the great skua Stercorarius skua breedsin Iceland.future. Although eagles have increased slightly in number due toconservation efforts, now numbering 40-45 pairs, the population is farsmaller than the estimated 150 pairs of a century ago. The thirdindigenous raptor species, the merlin (Falco columbarius), has a goodsizedbreeding population.Owls are represented by two species. The snowy owl (Nycteascandiaca) is an irregular breeder that has nested only a few timesduring the last 45 years, although seen annually as a straggler. Theshort-eared owl (Asio flammeus) occupies low-lying moors, and is oneof nine species of birds that started to breed in the country during theclimatic amelioration in the first half of this century. The other eightspecies include the shoveler (Anas clypeata), the tufted duck (Aythyafuligula), the pochard (Aythya ferina), the lesser black-backed gull (Larusfuscus), the herring gull (Larus argentatus), the common gull (Larus canus),the black-headed gull (Larus ridibundus) and the starling (Sturnusvulgaris). The Iceland gull (Larus glaucoides) is a regular and commonwinter visitor. Most of the gull populations have increased in size,while those of the arctic skua (Stercorarius parasiticus) and the great skua(Stercorarius skua) have remained stable. The Icelandic population ofthe last-mentioned species represents nearly half of the world breedingpopulation.The gyrfalcon's main prey is the rock ptarmigan (Lagopus mutus),the country's only gallinaceous bird and also its most important gamebird. The ptarmigan is one of the so-called cyclic species, which meansthat its population is subject to regular fluctuations. The length of thecycle in Iceland is about 10 years. In peak years, the ptarmigan appearsin large numbers over the whole country, but during periods ofscarcity, the population is reduced three- to fourfold.The striking paucity of nesting passerines, which are representedby only ten species, is no doubt primarily due to lack of suitablehabitats, especially the absence of forests, and to fluctuations in insect15