Relative importance of multiple plumage ornaments as status signals in golden whistlers (Pachycephala pectoralis)
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Status signals are traits that advertise an individual’s competitive abilities to conspecifics during aggressive disputes. Most studies of status signals in birds have focussed on melanin-based plumage signals, but recent research shows that carotenoid-based signals may also play a role in aggressive signaling. We assessed the relative importance of melanin- and carotenoid-based plumage patches as agonistic signals in a small passerine, the golden whistler (Pachycephala pectoralis). Display signals in male golden whistlers include an unpigmented white throat patch, a carotenoid-based yellow breast and nape band, and a melanin-based black chin-stripe. We found that only the white throat patch was correlated with contest-related attributes. Males possessing large throat patches defended larger territories and commenced breeding earlier. When caged males with either experimentally reduced, or unmanipulated throat patches were presented to conspecifics, those with experimentally reduced patches attracted less aggression from male subjects. Focal males also responded faster to caged males with throat patches similar in size to their own, suggesting that they may assess relative throat patch size before engaging in aggressive encounters. Females did not discriminate between “reduced” or “control” treatments. Our data strongly suggest that only the unpigmented throat patch functions as a status signal. As this signal is unlikely to have significant development costs, honesty may be maintained through social costs.
KeywordsGolden whistlers Status signals Plumage coloration Social costs Simulated territory intrusions
We are very grateful to Larissa Yocom, Saskia van Dongen, and Robert Ramiarison for their assistance with field work for this project. We thank Brian Elbers and Kees Müller for providing cages to house the captive whistlers, Staffan Andersson for conducting the carotenoid analysis of the whistler feathers, and Ian Gordon for his helpful statistics advice. Thank you to Grainne Maguire, Peter Dunn, and three anonymous referees for reading earlier drafts of this manuscript. This research was funded by the Holsworth Wildlife Research Fund, the Loftus-Hills Memorial Fund, the Stuart Leslie Bird Research Award, the Linnean Society of NSW, the Department of Zoology, University of Melbourne, and the David Hay Memorial Fund. Experiments were conducted under Animal Experimentation and Ethics Register 01011 from the University of Melbourne and permits from the Department of Sustainability and Environment, Australia.
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