Ardea
Official journal of the Netherlands Ornithologists' Union

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Bojarinova J.G., Rymkevich T.A. & Smirnov O.P. (2002) Timing of autumn migration of early and late-hatched Great Tits Parus major in NW Russia. ARDEA 90 (3): 401-409
We analysed the relationship between the timing of hatching and the timing of autumn migration in first and second brood Great Tit Parus major young. Second brood birds were recognised in autumn by the incomplete moult of their tail feathers. In first broods, the timing of migration in autumn is strongly related to the population median hatching date of first broods: first brood young migrate at a constant age independent of hatching date. When reproduction is delayed, migration is delayed to the same extent. Second brood birds migrate later in the season and are on average four weeks younger compared to first brood young. In contrast to first broods, the migration age in second brood young decreased with hatching date, resulting in a relatively constant migration date. Within second broods, young hatched after mid July migrate about 10 d younger than those hatched in the first half of the month. We discuss the annual variation in timing of migration in birds of different hatching dates in relation to the timing of the post-juvenile moult and its photoperiodical regulation


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