Ardea
Official journal of the Netherlands Ornithologists' Union

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Bulyuk V.N. (2006) At what time of the day do passerine nocturnal migrants arrive at their breeding sites? ARDEA 94 (1): 132-139
The navigational abilities of migratory birds are stunning, yet little is known about the environmental cues and behavioural mechanisms which lead to a pin-point termination of migration. This paper reports the data on 10 individual passerine nocturnal migrants (six Reed Warblers Acrocephalus scirpaceus, three Marsh Warblers A. palustris and one Lesser Whitethroat Sylvia curruca) recaptured on the Courish Spit on the Baltic Sea in 19982002 in high mist nets at the site where they had been ringed 17 years earlier. It is assumed that all these birds were captured at completing their nocturnal migratory flight. Capture histories of these birds show that they had hatched and/or bred at the recapture site, or occurred there during the breeding or post-breeding period. Most birds (seven out of 10) arrived to their presumed breeding site 12060 min before sunrise, whereas the remaining three arrived 240180 min before sunrise. These data support the hypothesis (Bolshakov & Bulyuk 1999) that when approaching their migratory target, nocturnally migrating passerines can rather precisely determine distance to their goal and adjust departure time in order to arrive in morning twilight. Captures of some birds during the most dark period suggest that in spite of limited visibility, the birds can identify their target in flight and land very precisely. It is also suggested that some migrants might find their breeding sites during diurnal movements after completing nocturnal migration in the vicinity of their target.


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