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A polar system of intercontinental bird migration
Thomas Alerstam1, Johan Bäckman, Gudmundur A Gudmundsson
1Department of Animal Ecology, Lund University, Ecology Building, 223 62 Lund, Sweden. thomas.alerstam@zooekol.lu.se
Proceedings. Biological Sciences
|August 10, 2007
Summary
Millions of birds migrate across the Arctic Ocean between Eurasia and North America. This study reveals a major Siberian-American bird migration system, with birds using great circle orientation for long-distance flights.
Area of Science:
- Ornithology
- Arctic Ecology
- Evolutionary Biology
Background:
- Beringia is crucial for understanding bird migration between Eurasia and North America.
- Polar bird migration offers insights into orientation and evolutionary connectivity.
- Previous studies lacked a comprehensive view of Arctic migratory systems.
Purpose of the Study:
- To investigate bird migratory flights in the Beringia region.
- To reconstruct a major Siberian-American bird migration system.
- To evaluate orientation principles and evolutionary factors in polar migration.
Main Methods:
- Tracking radar deployed on the ice-breaker Oden.
- Data collected from July 30 to August 19, 2005.
- Integration of Beringia data with Arctic Ocean and Beaufort Sea radar studies.
Main Results:
- Extensive bird migration observed across Beringia (64°N to 75°N).
- Eastward flights constituted 79% of all track directions.
- Reconstructed a Siberian-American migration system involving over 2 million birds (shorebirds, terns, skuas).
- Birds flew over the Arctic Ocean at altitudes exceeding 1 km.
- Great circle orientation better explained flight directions than compass orientation.
- Long sea flights covered 1400-2600 km over 26-48 hours.
- Migration connected to American and Pacific flyway systems.
Conclusions:
- A major bird migration system spans the Arctic, connecting continents.
- Great circle orientation is key for long-distance Arctic flights.
- Evolution of this system is influenced by distance minimization and glacial history.
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