Energy expenditure, nestling age, and brood size: an experimental study of parental behavior in the great tit Parus major |
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Authors: | Sanz Juan J; Tinbergen Joost M |
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Institution: | Zoological Laboratory, University of Groningen, PO Box 14, 9750 AA Haren,
The Netherlands |
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Abstract: | A brood manipulation experiment on great tits Parus major was
performedto study the effects of nestling age and brood size on parentalcare
and offspring survival. Daily energy expenditure (DEE)of females feeding
nestlings of 6 and 12 days of age was measuredusing the doubly-labeled water
technique. Females adjusted theirbrooding behavior to the age of the young.
The data are consistentwith the idea that brooding behavior was determined
primarilyby the thermoregulatory requirements of the brood. Female DEEdid
not differ with nestling age; when differences in body masswere controlled
for, it was lower during the brooding periodthan later. In enlarged broods,
both parents showed significantlyhigher rates of food provisioning to the
brood. Female DEE wasaffected by brood size manipulation, and it did not
level offwith brood size. There was no significant effect of nestlingage on
the relation between DEE and manipulation. Birds wereable to raise a larger
brood than the natural brood size, althoughlarger broods suffered from
increased nestling mortality ratesduring the peak demand period of the
nestlings. Offspring conditionat fledging was negatively affected by brood
size manipulation,but recruitment rate per brood was positively related to
broodsize, suggesting that the optimal brood size exceeds the naturalbrood
size in this population. |
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Keywords: | brood size manipulation doubly-labeled water technique energy expenditure great tits parental care Parus major |
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