Influence of body condition and weather on departures of first-year European robins, <Emphasis Type="Italic">Erithacus rubecula</Emphasis>, from an autumn migratory stopover site |
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Authors: | Arseny Tsvey Victor N Bulyuk Vlad Kosarev |
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Institution: | (1) Biological Station Rybachy of Zoological Institute RAS, Biological Station Rybachy, Rybachy, 238535 Kaliningrad Region, Russia |
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Abstract: | How migratory birds decide when to leave a stopover site is important to the understanding of bird migration strategies. Our
study looks at how body condition and the weather affect the decision to depart on nocturnal migratory flight. During two
autumn migration seasons (2002–2003), we radio tracked 51 first-year European robins, Erithacus rubecula, at a stopover site on the Courish Spit (Eastern Baltic) from the first day after landing until their migratory departure.
The tagged robins stopped over for 1–14 days. There was no clear relationship between stopover duration and energetic condition
on arrival. Weather conditions (wind, precipitation, and cloud cover) on departure differed measurably between years. In 2002,
robins took off mainly under following winds and clear skies. In 2003, there were mainly light head winds and partially cloudy
or overcast skies. This could be explained by the year-specific role of weather factors in making the decision to depart.
In both years, robins making short (1–2 days) stopovers took off in more varied weather situations than those individuals
with long stopovers. This suggests that robins from the former group were more inclined to continue with migration than longer-stay
birds that, apart from re-fuelling, could be waiting for favourable weather. The lack of a relationship between stopover duration
and body condition and some departures under unfavourable weather conditions suggest that endogenous spatiotemporal programmes
may play an important role in controlling stopover duration in robins. |
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Keywords: | European robin Erithacus rubecula Stopover duration Departure decision |
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