17 research outputs found

    Phenotypic plasticity in nest departure calls: Weighing costs and benefits

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    In birds, male song has been extensively studied, but female vocalizations have received little attention. Females of several North American species produce a unique vocalization, the nest departure call (NDC), upon leaving nests. Producing NDCs has costs due to acoustical properties that make nests easy to locate by predators. Thus, NDCs must also have benefits that balance or outweigh costs, and females should modulate call production as costs and benefits change. We explored whether female song sparrows, Melospiza melodia, adjust calling rate to reflect differential costs and benefits of calling induced by male presence, male quality (measured by body mass and song complexity), nest predator presence and nest height. Results suggest that calls benefit females by promoting male nest guarding and that females display adaptive plasticity in call production. Specifically, calling rate increased when the male was present, and male nest guarding increased when females gave an NDC. Females called less in the presence of a model nest predator, probably because the perceived costs of predator attraction outweighed the benefits of male recruitment. Conversely, females with heavier mates called more, perhaps because the efficacy of male nest guarding increases with mass. In addition, females called more from elevated nests in the presence of the predator and decreased calling later in the day. Male song complexity failed to predict calling rate, suggesting that this sexually selected trait does not reflect direct benefits gained by producing an NDC. Plasticity in calling probably exists because context-appropriate communication elevates fitness, whereas contextual mistakes in the decision to communicate result in fitness declines. © 2014 The Association for the Study of Animal Behaviour

    Phaeomelanin- and carotenoid-based pigmentation reflect oxidative status in two populations of the yellow warbler (Setophaga petechia)

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    Carotenoid- and phaeomelanin-based sexual pigmentation may signal a capacity to maintain oxidative balance and viability. However, diverse empirical results leave the association between pigmentation and oxidative stress (OS) unclear. We assessed the hypothesis that population-specific levels of oxidative challenge, or strategies for managing OS, affect relationships between sexual pigmentation and OS. Specifically, intense oxidative challenge in migratory, temperate breeding birds might enhance correlations between pigmentation and OS relative to allied tropical breeders, since quality-based differences in OS may arise only under intense oxidative challenge. Alternatively, in temperate breeders with intense within-season reproductive effort, high-quality birds may invest in reproduction over oxidative balance, dampening negative correlations between pigmentation and OS. To assess these alternatives, we compared prenesting relationships between pigmentation and OS in a migratory, Californian population of yellow warblers (Setophaga petechia brewsteri) and in a resident, Mexican population (Setophaga petechia bryanti, "mangrove warblers"). Yellow warblers displayed higher OS than mangrove warblers. However, year of capture and sex had bigger influences on correlations between pigmentation and OS than population. Males with more intense melanin pigmentation had lower OS among mangrove warblers and yellow warblers captured in 2011, but not among yellow warblers captured in 2012. In females only, lower OS levels were associated with more colorful carotenoid pigmentation. Results suggest that both phaeomelanin- and carotenoid-based pigmentation have the potential to correlate with OS levels, but that the signaling potential of pigmentation may shift with inter-annual variation in environmental conditions and display sex-specific dynamics. © 2014 Springer-Verlag Berlin Heidelberg
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