The effect of rearing environment on blue structural coloration of eastern bluebirds (<Emphasis Type="Italic">Sialia sialis</Emphasis>) |
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Authors: | Lynn Siefferman Geoffrey E Hill |
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Institution: | (1) Center for the Integrative Study of Animal Behavior, Indiana University, 402 N. Park Ave., Bloomington, IN 47405, USA;(2) Department of Biological Sciences, Auburn University, 331 Funchess Hall, Auburn, AL 36849, USA |
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Abstract: | We used a brood-size manipulation to test the effect of rearing environment on structural coloration of feathers grown by
eastern bluebird (Sialia sialis) nestlings. Ultraviolet (UV)-blue structural coloration has been shown to be sexually selected in this species. Our experimental
design took advantage of the growth of UV-blue wing feathers in nestlings that are retained as part of the first nuptial plumage.
We cross-fostered nestlings to create enlarged and reduced broods with the purpose of manipulating parental feeding rates
and measured the effect on nestling growth and plumage coloration. Brood size influenced feeding rates to offspring, but the
effect varied with season. In general, male nestlings reared in reduced broods were fed more often, weighed more, and displayed
brighter structural plumage compared to nestlings reared in enlarged broods. Female nestlings appeared to experience less
adverse affects of brood enlargement, and we did not detect an effect of brood-size manipulation on the plumage coloration
of female nestlings. Measures of plumage coloration in both males and females, however, were correlated to hatching date and
nestling mass during feather development. These data provide empirical evidence that environmental quality can influence the
development of the blue structural coloration of feathers and that males may be more sensitive to environmental fluctuations
than females. |
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Keywords: | Structural plumage coloration Condition-dependent traits Sexual selection Parental care Parental effects |
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