Sexually selected male plumage color is testosterone dependent in a tropical passerine bird, the red-backed fairy-wren (Malurus melanocephalus)

Willow R Lindsay; Michael S Webster; Hubert Schwabl

doi:10.1371/journal.pone.0026067

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Sexually selected male plumage color is testosterone dependent in a tropical passerine bird, the red-backed fairy-wren (Malurus melanocephalus)

Willow R Lindsay, Michael S Webster and Hubert Schwabl

PloS one, Vol.6(10), pp.e26067-e26067

2011

DOI: https://doi.org/10.1371/journal.pone.0026067

Handle:

https://hdl.handle.net/2376/104363

PMCID: PMC3187837

PMID: 21998753

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Abstract

Organ Size

Male

Pigmentation

Passeriformes - growth & development

Sexual Behavior, Animal - physiology

Feathers - anatomy & histology

Passeriformes - anatomy & histology

Passeriformes - metabolism

Testosterone - metabolism

Phenotype

Animals

Female

Corticosterone - metabolism

Androgens - metabolism

Sexual signals, such as bright plumage coloration in passerine birds, reflect individual quality, and testosterone (T) may play a critical role in maintaining signal honesty. Manipulations of T during molt have yielded mixed effects on passerine plumage color, in most cases delaying molt or leading to production of drab plumage. However, the majority of these studies have been conducted on species that undergo a post-nuptial molt when T is low; the role of T in species that acquire breeding plumage during a pre-nuptial molt remains largely unexplored. We experimentally tested the effects of increased T on plumage color in second-year male red-backed fairy-wrens (Malurus melanocephalus), a species in which after-second-year males undergo a pre-nuptial molt into red/black (carotenoid and melanin-based) plumage and second-year males either assume red/black or brown breeding plumage. T treatment stimulated a rapid and early onset pre-nuptial molt and resulted in red/black plumage acquisition, bill darkening, and growth of the sperm storage organ, but had no effect on body condition or corticosterone concentrations. Control males molted later and assumed brown plumage. T treated males produced feathers with similar but not identical reflectance parameters to those of unmanipulated after-second-year red/black males; while reflectance spectra of red back and black crown feathers were similar, black breast feathers differed in UV chroma, hue and brightness, indicating a potentially age and plumage patch-dependent response to T for melanin- vs. carotenoid-pigmentation. We show that testosterone is the primary mechanism functioning during the pre-nuptial molt to regulate intrasexually variable plumage color and breeding phenotype in male red-backed fairy-wrens. Our results suggest that the effects of T on plumage coloration may vary with timing of molt (pre- vs. post-nuptial), and that the role of T in mediating plumage signal production may differ across age classes, plumage patches, and between pigment-types.

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Title: Sexually selected male plumage color is testosterone dependent in a tropical passerine bird, the red-backed fairy-wren (Malurus melanocephalus)
Creators: Willow R Lindsay - School of Biological Sciences and Center for Reproductive Biology, Washington State University, Pullman, Washington, United States of America
Michael S Webster
Hubert Schwabl
Publication Details: PloS one, Vol.6(10), pp.e26067-e26067
Academic Unit: Biological Sciences, School of
Publisher: United States
Identifiers: 99900546805101842
Language: English
Resource Type: Journal article