BIOLOGICAL DIVERSITY IN ICELAND - Convention on Biological ...

the few places where the whooper swan (Cygnus cygnus) can be called acommon breeding bird. It most frequently inhabits lake-dotted highgrounds on the borders of the Central Highlands.Seabirds represent one of the most important elements ofIceland's bird fauna. Most of the seabirdpopulations are of internationalimportance because of the number ofindividuals, which represent large and insome cases substantial parts of worldpopulations. On the towering bird-cliffs,which are occupied by a mixedassemblage of colonial seabirds, the mostimportant species are the commonguillemot (Uria aalge), Brünnich'sguillemot (Uria lomvia), the razorbill (Alcatorda), the kittiwake (Rissa tridactyla), and the fulmar (Fulmarus glacialis).The three largest bird-cliffs, Látrabjarg, Hælavíkurbjarg, andHornbjarg, are all in the north-west, and are among the largestseabird-cliffs in the North Atlantic. Although also found on bird-cliffs,the puffin (Fratercula arctica), primarily inhabits grassy islands, and isprobably the most common Icelandic bird. The black guillemot(Cepphus grylle) is less gregarious than the other auk species and nestssparsely in screes. The gannet (Sula bassana), the queen of the NorthAtlantic, nests mainly on rocky offshore islands and stacks. All theseseabird species inhabit the Westmann Islands, off Iceland's southcoast, together with three procellariform species, which are hardlyfound elsewhere in Iceland, Leach's petrel (Oceanodroma leucorrhoa), thestorm petrel (Hydrobates pelagicus), and the manx shearwater (Puffinuspuffinus). The arctic tern (Sterna paradisaea) is one of Iceland's mostcommon seabird species, with colonies in all parts of the country,especially in coastal regions.Freshwater FishFigure 7. One of the mostnumerous bird in Iceland isthe puffin, Fratercula arcticawith approximately 1,000,000breeding pairs.The productivity of rivers varies greatly according to their location,water source, volume of flow, length, gradient and water temperature,especially in the summer months. Rivers that have lakes as their sourceor that flow through lakes prove generally more productive thanothers. Lake productivity also varies greatly and is influenced by manyfactors: the geology of the surroundings, water temperature, depth,altitude above sea-level, quantity of nutrients, precipitation andrenewal of lake water. Icelandic watersheds have been classified intoecological classes based on these factors, each class having its distinct17