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The Razorbill, Alca torda, is a large auk, 38-43 cm in length, with a 60-69 cm wingspan. It is the only living member of the genus Alca.

Adult birds are black on their upperparts and white on the breast and belly. The thick black bill has a blunt end. The tail is pointed and longer than that of a Murre. In winter, the throat and upper chest turn white.

Their breeding habitat is islands, rocky shores and cliffs on northern Atlanticmarker coasts, in eastern North America as far south as Mainemarker, and in western Europe from northwestern Russiamarker to northern Francemarker. North American birds migrate offshore and south, ranging from the Grand Banksmarker of Newfoundlandmarker to New Englandmarker. Eurasian birds also winter at sea, with some moving south as far as the western Mediterraneanmarker.

These birds forage for food by swimming underwater. Razorbills can stay underwater for about one minute before surfacing. Razorbills catch their prey and eat them underwater. They mainly eat fish, like sandeels, herring and capelin, also some crustaceans and marine worms. Razorbills usually nest in large colonies and lay their eggs on bare rock or ground. Each partner will forage, then come home to take over with caring for the egg or young. When feeding their young, they will hold several fish in their bill and fly back to the nesting cliff. They may well fly more than 100 km out to sea to feed when during egg incubation, but when provisioning the young, they forage closer to the nesting grounds, some dozen kilometers away, and often in shallower water (2003): Can surveillance radar be used to monitor the foraging distribution of colonially breeding alcids? [English with Spanish abstract] Condor 105(1): 145–150. DOI: 10.1650/0010-5422(2003)105[145:CSRBUT]2.0.CO;2 HTML abstract .

Though the Razorbill's average lifespan is roughly 13 years, a bird ringed in the UK in 1967 has survived for at least 41 years—a record for the species.

Well-known Razorbill colonies include:
  • Heligolandmarker, Germany (54°10' N) - near southern limit in Europe, a few pairs only
  • Staple Islandmarker, Outer Farne Islandsmarker, UKmarker (55°38' N) - breeding season May to mid-July.
  • Rundemarker, Norway (62°24' N) - 3,000 pairs
  • Látrabjargmarker, Iceland (65°30' N) - 230,000 pairs, about 40% of the global population (mid-1990s estimate). Breeding season June - July.
  • Grímseymarker, Iceland (66°33' N)


Evolution and prehistoric species

While the Razorbill is the only living species, the genus Alca had a much higher diversity in the Pliocene. A number of fossil forms have been found:

  • Alca "antiqua" (Late Miocene/Early Pliocene of Lee Creek Mine, USA)
  • Alca sp. (Late Miocene/Early Pliocene of Lee Creek Mine, USA) - possibly A. stewarti
  • Alca stewarti (Kattendijk Sands Early Pliocene of Belgium)
  • Alca ausonia (Yorktown Early Pliocene of Lee Creek Mine, USA - Middle Pliocene of Italy)
  • Alca sp. (Puerto de Mazarrón Pliocene of El Alamillo, Spain) - may be A. antiqua or A. ausonia


As far as is known, the genus Alca seems to have evolved in the western North Atlantic or the present-day Caribbeanmarker like most other Alcini. Its ancestors would have reached these waters through the still-open Isthmus of Panama during the Miocene (1985): Evolution and characteristics of the Atlantic Alcidae. In: , The Atlantic Alcidae: 6-19. Academic Press, London. ISBN 0-12-515671-5 .

References




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