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Reed warbler orientation: initiation of nocturnal migratory flights in relation to visibility of celestial cues at dusk

Författare

Summary, in English

We used radiotelemetry to investigate the time of migratory flight initiation relative to available celestial orientation cues and departure direction of a nocturnal passerine migrant, the reed warbler, Acrocephalus scirpaceus, during autumn migration. The study was carried out at Falsterbo, a coastal site in southwest Sweden. The warblers initiated migration from times well after local sunset and well into the night, corresponding to sun elevations between - 4 degrees and - 35 degrees, coinciding with the occurrence of stars at night. They departed in the expected migratory direction towards south of southwest with a few initiating migration in reverse directions towards northeast to east. Flight directions under overcast conditions (7-8/8) were more scattered than under dear sky conditions (0-4/8). There were fewer clouds on departure nights than on nights when the birds did not initiate migration. For birds staying longer than one night at stopover the horizontal visibility was higher and precipitation was less likely on departure nights than on the previous night. The results show that the visibility of celestial cues, and stars in particular, are important for the decision to initiate migration in reed warblers. However, cloud cover, horizontal visibility and precipitation might be correlated with other weather variables (i.e. wind or air pressure) that are also likely to be important for the decision to migrate. (C) 2001 The Association for the Study of Animal Behaviour.

Publiceringsår

2001

Språk

Engelska

Sidor

181-189

Publikation/Tidskrift/Serie

Animal Behaviour

Volym

61

Issue

1

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Biological Sciences

Status

Published

Forskningsgrupp

  • Animal Navigation Lab

ISBN/ISSN/Övrigt

  • ISSN: 1095-8282