Daily patterns of nest visits are correlated with ambient temperature in the Northern Wheatear |
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Authors: | Matthew Low S?nke Eggers Debora Arlt and Tomas P?rt |
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Institution: | (1) Department of Ecology, Swedish University of Agricultural Sciences, PO Box 7044, 750 07 Uppsala, Sweden;(2) Department of Ecology, Swedish University of Agricultural Sciences, PO Box 7002, 750 07 Uppsala, Sweden |
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Abstract: | The diurnal pattern of foraging behaviour in birds is commonly linked to the risk of starvation and predation. During the
breeding season, when offspring place additional demands on the quantity of food adults need to collect, diurnal foraging
patterns may be influenced to a greater extent by food availability because adults need to balance starvation–predation risks
not only for themselves but also their offspring. We used data-loggers to measure diurnal variation in rates of nest visits
to 7- to 10-day-old nestlings of the insectivorous Northern Wheatear Oenanthe oenanthe in Swedish farmland habitat. Adults provisioned the nestlings with food for an average 19.5 h each day (n = 11 pairs), with visitation rates sharply increasing during the morning, remaining relatively stable between 0800 and 1700 hours,
and then declining in the evening. This pattern is similar to daily temperature fluctuations and is consistent with the hypothesis
that nest visit rates are a function of temperature-dependent prey availability. Higher rates of nest visits on warm days
support this correlation between temperature and offspring feeding. However, without data on the rate of self-feeding by adults
it is difficult to distinguish between patterns of nest visits being driven by food availability, or starvation–predation
constraints being imposed on the parents; thus, future studies of patterns of offspring feeding should collect data on the
self-feeding behaviour of the adults. |
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Keywords: | Diurnal variation Offspring provisioning Feeding rate Food availability Starvation– predation risk |
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