Synchronizing feather-based measures of corticosterone and carotenoid-dependent signals: what relationships do we expect?

• Published in: Oecologia Vol. 174; no. 3; pp. 689 - 698
• Main Authors: Fairhurst, Graham D, Dawson, Russell D, van Oort, Harry, Bortolotti, Gary R
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-03-2014; Springer; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: Adults; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Biological and medical sciences; Biomedical and Life Sciences; Birds; Carotenoids; Carotenoids - metabolism; Color; Colors; correlation; Corticosterone; Corticosterone - metabolism; Ecology; Feathers; Feathers - metabolism; Female; females; foraging; Foraging behavior; Fundamental and applied biological sciences. Psychology; General aspects; Hydrology/Water Resources; Life Sciences; Male; Male animals; males; Oxidative stress; Passeriformes - growth & development; Passeriformes - metabolism; Physiological aspects; PHYSIOLOGICAL ECOLOGY; Physiological ecology - Original research; Pigmentation - physiology; Plant Sciences; Plumage; probability; Signal reflection; Steroids; Common redpoll; Carotenoid-dependent plumage color; Feather quality; Corticosterone; Acanthis flammea; Signal; Quality; Color; Feather; Plumage; Carotenoid
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-013-2830-5

Carotenoids produce many of the red, orange and yellow signal traits of birds, and individuals must trade off utilizing carotenoids for physiological processes versus ornamentation. Proximate mechanisms regulating this trade-off are poorly understood, despite their importance for expression of color signals. Corticosterone (CORT) may play a significant mechanistic role in signal expression because it mobilizes energy substrates and influences foraging behavior. We used a unique feather-based approach to test whether CORT mediates expression of carotenoid-based coloration. First, we investigated relationships between levels of CORT from feathers (CORTf) and carotenoid-based plumage signals in common redpolls (Acanthis flammea). Then, we determined how the width of growth bars and probability of having fault bars on feathers varied with CORTf, specifically whether these metrics reflected developmental costs of elevated CORT (“stress” hypothesis) or represented an individual’s quality (“quality” hypothesis). CORTf correlated positively with the strength of carotenoid signals, but only in adult males. However, also in adult males, CORTf was positively related to width of feather growth bars and negatively with probability of having fault bars, providing support for the quality hypothesis. Overall, CORTf was lower in adult males than in females or young males, possibly due to dominance patterns. Our results indicate that CORT may indirectly benefit feather quality, potentially by mediating the expression of carotenoid signals. We place our sex-specific findings into a novel framework that proposes that the influences of CORT in mediating carotenoid-based plumage traits will depend on the extent to which carotenoids are traded off between competing functions.