Autumn departure of adult nocturnally migrating passerines from their breeding sites. Avian Ecol Behav

Abstract

Due to methodical problems it is very difficult to obtain information on where, when and in which condition individual passerines take off for their first nocturnal migratory flight towards winter quarters in autumn or towards breeding grounds in spring. This paper reports the data on eight adult individual passerine nocturnal migrants (six Reed Warblers Acrocephalus scirpaceus, one Blackcap Sylvia atricapilla, and one Whitethroat S. communis) recaptured on the Courish Spit on the Baltic Sea in 1997-2002 in high mist nets at night during autumn migration. Capture histories of these birds suggest that they had been breeding at the capture site, therefore their recapture at nocturnal take-off could be related to their nocturnal migratory departure towards winter quarters. Five of eight adult migrants departed in the second or third hours into the night after sunset. The remaining three individuals took off in the second half of the night. Fuel stores of these birds varied between 8.3% and 24.3% of their lean body mass. Nocturnal flights of all migrants were started under winds favourable for migration