Article Abstract:
A study was conducted on a breeding population of Yellow Warblers to determine the validity of Lack's brood-reduction hypothesis on hatching asynchrony. Results were generally consistent with the hypothesis, in that nestling mortality was greater in last-hatched nestlings in asynchronously-hatched broods and was random in synchronous broods. In addition, first-hatched chicks from asynchronous broods showed higher fledging mass, survival rates and fledging-to-clutch ratios. However, in contrast to the hypothesis, last-hatched chicks from both brood types had similar survival rates and fledging mass.
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Article Abstract:
A study in avian biology focused on variations in egg size and the effects of egg size on the Snow Petrel's early nestling growth. The Snow Petrels, which bred at Svarthamaren in Dronning Maud Land, Antarctica, produced eggs that were 36.4 cm. to 52.1 cm. when measured. An exchange of eggs between nests, the analyses of non-manipulated nests and other experimental procedures showed that egg size affected the nestling body masses of two- and four-day old chicks.
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Article Abstract:
Pairs of breeding red-faced warblers, Cardellina rubrifrons, were monitored to investigate the interaction between paired birds and the response of the birds to intrusions by another male. Most intrusions occurred during the nest-building stage and the male partner responded assuming a position that will bring him closer to his mate. This pattern of behavior persists even beyond the fertile period. Possible explanations for this behavior are presented.
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