Red-legged Kittiwake
Clip Gulls on Saint George in Alaska
The Klippenmöwe (Rissa brevirostris ) is a medium sized sub-Arctic species of bird in the family of gulls ( Laridae ) and is classified together with the kittiwake (Rissa tridactyla) in the genus Rissa.
The IUCN classifies the Klippenmöwe now as vulnerable ( vulnerable ) because, there has been over the last four decades a significant population decline. The stock is a maximum of 500,000 mature individuals and seems to have stabilized lines in recent years. It is therefore possible that the IUCN changes the status to potentially at risk ( near threatened ).
Features
The 36 to 39 centimeters Klippenmöwe is easily confused with the slightly larger Kittiwake. In breeding plumage the head, neck, tail, fuselage, and the largest part of the wings are white. The back and upper wing surface are dark gray, the tips of the outer primaries are black. Differentiators for Kittiwake are the coral legs and feet, which are predominantly black in the kittiwake, the shorter yellow beak and dark gray top. Her dark brown eyes are slightly larger than those of the Kittiwake. Outside the breeding season, gulls carry clip on both sides of the head behind the eye a diffuse black spot. Young gulls clip in the first year are similar to adult birds in appearance. However, they have a black beak and can be distinguished by the white tail feathers of other young birds related species.
Nutrition
Clip gulls feed mainly on planktonic small fish, squid, crustaceans and mollusks. In their raids they often hunt together with the kittiwake. They pursue their dense floating below the water surface prey on the water surface, or earn them from the water surface. Due to their larger eyes they also have the advantage of being able to view and hunt fish at dusk or at night.
Reproduction
Hatched in large colonies along with other bird species such as, among others, the kittiwake (Rissa tridactyla), the thick-billed murre (Uria lomvia ), the Horned Puffin (Fratercula corniculata ), the Rotschnabelalk ( Aethia psittacula ) or the Tufted Puffin (Fratercula cirrhata ). Your mud and grass nests they build on the cliffs along the coast on small ledges and rock bands preferably under overhangs and in the higher regions clip from a height of 200 to 300 meters. They relate this very narrow bands of rock and thus not be in competition with kittiwakes who prefer wider bands for nest plant. On their breeding grounds, the clip gulls are relatively safe from mammalian predators. A nest consists of an egg; rarely two eggs. At the nest, as well as to the business of breeding and rearing both adult birds are involved. The chicks leave the nest after about five weeks. Take the young birds during the development period too little to lipid-rich food on, they grow slower and produce more stress hormones.
Dissemination
The Klippenmöwe in contrast to the Kittiwake only a very small area of distribution. The species is found only on the Bering Sea, the breeding colonies are limited to four places: belonging to Alaska Bogoslof Islands, the Pribilof Islands and the Buldir Island and the Russian Commander Islands. More than 75 % of the stock breeds on the belonging to the Pribilof Island of St. George. Since the seventies, the inventory of breeding pairs has declined sharply. However, recent studies, the stocks recover slowly. After the young birds have left the nest, pull the adult birds until the next breeding season on the open Bering Sea. Little is known about their way of life in the winter areas.
Causes of population decline
Adolescents cliff seagulls need a certain amount of fats in their diet. Climate change decimated the number of fat-rich fish prey and there was an oversupply of low-fat fish. Since the holdings of other seabird species in the Bering Sea in the North Pacific have declined since the 70s and the lack of young talent for the conservation of populations could be ruled out, scientists have studied how the warming of the Bering Sea and the resulting lack of available high-fat prey fish affect the stocks could.