Investigations of delayed plumage maturation in the orchard oriole

I investigated delayed plumage maturation (DPM) in the orchard oriole Icterus spurius), a dichromatic neo-tropical migrant in which first year males possess a distinct non-definitive plumage. I used model/playback experiments to test predictions of alternative breeding season signaling hypotheses for DPM. I found that, contrary to the results of several previous studies, subadult plumage in the orchard oriole does not reduce intra-sexual aggression directed toward subadults during the breeding season. I attribute these different results to differences among species in the reliability of plumage cues of sex and age. In a second study, I examined winter adaptation hypotheses for DPM. I conducted focal animal observations of foraging orioles during the non-breeding season in Panama in order to evaluate predictions of the winter status signaling hypothesis, and I found that, contrary to this hypothesis, subadult male plumage reduced neither the frequency or intensity of adult male aggression during the winter. While in Panama, I also examined the molt characteristics of orioles in order to test predictions of the molt constraint hypothesis. I found that the majority of feathers grown by subadult males during the presumed per-alternate molt were of non-definitive coloration, contrary to predictions of molt constraint hypothesis. Finally, I tested female preference for age specific plumage characteristics. I found that females preferred adult males to subadult males in choice experiments with both live and model males.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Enstrom, David A.

Contributors dc:contributor

• Robinson, Scott K.
• Burley, Nancy

• Biology, General
• Biology, Ecology
• Biology, Zoology

Statement dc:rights

• Copyright 1990 Enstrom, David Arthur

Language dc:language

eng

Identifier

AAI9026176
(UMI)AAI9026176

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/22856