Environmental and genetic effects on pigment-based vs. structural component of yellow feather colouration.

Carotenoid plumage is of widespread use in bird communication. Carotenoid-based feather colouration has recently been shown to be dependent on both pigment concentration and feather structure. If these two components are determined differently, one plumage patch may potentially convey different aspects of individual quality.We evaluated the effects of genetic and environmental factors on carotenoid-based yellow breast colouration of Great Tit (Parus major) nestlings. By partial cross-fostering, we separated the genetic and pre-natal vs. post-natal parental effects on both the structural and the pigment-based component of carotenoid-based plumage colouration. We also simultaneously manipulated the post-hatching environment by brood size manipulation. The structural component of nestling colouration reflected features of female colouration. On the other hand, the pigment-based component was more affected by rearing conditions presumably representing food quality. While the structural component was related to both origin- and environment-related factors, the pigment-based component seemed to be environment-dependent only. These results support the notion that pigment-based and structural components of feather colouration are determined differently.Chromatic and achromatic components of carotenoid-based feather colouration reflected different aspects of individual quality and history, and thus may potentially form a multicomponent signal

Reflectance curve of Great Tit yellow breast feathers measured by objective spectrophotometry.

<p>Mean value (± SE) for females (n = 40) and nestlings (n = 296) is given. The wavelengths used to calculate absolute carotenoid chroma (–1× (R_400−515/R_575−700)) and background reflectance (ΣR_575−700) are highlighted in grey.</p

Linear mixed model explaining background reflectance of yellow breast feathers in Great Tit nestlings.

<p>For fixed effects, type 3 tests and denominator DF are presented, numerator DF = 1 in all cases. For random effects, covariance parameter estimates are presented (REML method). Likelihood ratio test of the overall significance of random effects: χ² = 39.9, DF = 3, P<0.001. P-values of significant factor are in bold.</p>*<p>Estimate for 1y old (relative to older) females.</p>**<p>Estimate for reduced (relative to enlarged) broods.</p>***<p>PC1 of yolk antioxidants included concentrations of vitamin A, vitamin E, lutein and zeaxanthin in egg yolk; all concentrations were log₁₀-transformed.</p

Overall effects of the rearing environment and rearing vs. genetic mother on colouration of Great Tit nestlings.

<p>Depicted are means (+ SE) of absolute values of standardized regression coefficients (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036640#pone-0036640-g002" target="_blank">Fig. 2</a>) to compare overall effect size regardless of effect direction. Environment includes hatching date, brood size manipulation and per-capita feeding rates. Effects of the rearing and the genetic mother include their age and colouration (absolute carotenoid chroma and background reflectance). Only fixed effect are included (a significant part of background reflectance is explained by nonspecific environmental condition, represented by the random effect of the nest of rearing).</p