January 12, 2010

Arctic Terns Followed During Winter Migration

Arctic terns migrating south for winter often take a rest for a few days off the coast of Newfoundland, before continuing their long journey south, according to the Associated Press.

The region where the small birds take their break was disclosed for the first time on Tuesday in Proceedings of the National Academy of Science. While the migration from the Arctic to the Antarctic is a well-known journey for the Arctic tern, the stopover point had been previously unknown by scientists and bird enthusiasts.

Carsten Egevang of the Greenland Institute of Natural Resources led the research that followed the movements of the terns using tiny geolocators they attached to the birds in Greenland and Iceland. The tiny, nearly weightless devices recorded the position and duration of the sun, which allowed researchers to calculate the tern's flight path once the devices were retrieved.

Researchers, who attached devices on 10 birds from Greenland and one from Iceland, analyzed the data and found that the birds paused at a deep water area of the North Atlantic for around 25 days before continuing on. Once leaving the oceanic rest area, the birds moved south, some along the coast of Africa, other along South America, until they reached the Antarctic during its summer season.

The previously unknown stopover was located at an area where the cold northern waters meet the warmer southern waters, researchers said.

The research was funded by the Commission for Scientific Research in Greenland, Greenland Institute of Natural Resources and National Environmental Research Institute, Aarhus University, Denmark.


Image 1: The Arctic tern (Sterna paradisaea) is an elegant flyer performing an annual long-distance migration between the Arctic and the Antarctica.

Image 2: Simplified figure showing migration patterns of the Arctic tern, from the breeding sites in Greenland and Iceland to the winter grounds at Antarctica. After initiating the southbound migration (yellow line) the birds paused their migration in the central part of the North Atlantic (small circle) for almost a month before they continue towards the wintering sites at Antarctica (large circle). In spring, the northbound migration (white line) is conducted more than twice as fast in a gigantic "S" shaped pattern through the Atlantic Ocean. Areas particular rich in biological productivity are indicated by yellow and green colors.


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