Diffuse, short and slow migration among Blue Tits |
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Authors: | Anna L K Nilsson Thomas Alerstam and Jan-?ke Nilsson |
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Institution: | (1) Department of Animal Ecology, Lund University, Ecology Building, 22362 Lund, Sweden |
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Abstract: | The knowledge of migration systems in long-distance regular migrants is in many cases extensive. Our understanding of the
migratory characteristics of partial migrants, on the other hand, is far more rudimentary. We investigated migratory characteristics
of partially migratory Blue Tits Cyanistes caeruleus using ringing recoveries of Swedish birds, to answer questions about geographic migration patterns, age-specific migrations,
migration speeds and synchrony of movements. Median migration distance of Swedish Blue Tits was 82 km, with a main autumn
direction in the sector between S and W (large directional scatter). Northerly and southerly populations did not differ in
migration directions or distances, suggesting chain migration to be the general pattern. A larger proportion of adult Blue
Tits remained near the breeding grounds during winter than was the case for juveniles. Some of the migrating birds (17%) seemed
not to return in spring but stayed to breed closer to the winter area. Swedish Blue Tits show an exceptionally slow migration
speed (median 13 km/day), among the slowest speeds recorded for any migrant bird. The Blue Tit represents an extreme case
of diffuse, short and slow bird migration. |
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Keywords: | Short-distance migration Timing of migration Adaptations to migration Partial migration |
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