nteractions and factors were sequentially removed from the models when non-significant (*p* \> 0.05) following a standard backward procedure. We report values from non-significant predictors removed from the full model and those for significant ones from the final model. Normality was tested with Kolmogorov--Smirnoff and steroids levels were log transformed as they did not reach the normal distribution. Data are reported as mean ± SE. We performed post hoc tests for detecting which hormone treatment differed from each other when the overall effect of treatment was significant (*p* \< 0.05). We performed post hoc tests detecting within which hormone treatment there was an effect of sex only when the interaction between sex and hormone treatment was significant, except for one case in which the data indicated lack of power for such an interaction. Post hoc tests were performed by using Fisher LSD tests after removing non-significant factors.

Results {#Sec12}
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Carotenoid characterization {#Sec13}
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The bare skin of the two periorbital rings contained a high concentration of xanthophylls (dehydrolutein, lutein, zeaxanthin, and lutein esters; Fig. [1](#Fig1){ref-type="fig"}) with the ones of the males having higher levels than the ones of the females (Table [1](#Tab1){ref-type="table"}). *Trans*-lutein and zeaxanthin, being present in the seeds, may have been acquired by the bird from the diet and deposited in tissues without any transformation, in contrast to *cis*-lutein and dehydrolutein which were lacking in the food. It is known that dehydrolutein can be converted from zeaxanthin and/or *cis*- and *trans*-lutein by oxidation (Gesa et al. [@CR24]). The skin also contained high concentrations of lutein esters (Table [1](#Tab1){ref-type="table"}; Fig. [1](#Fig1){ref-type="fig"}). The latter represented 92% of the female and 84% of the male total skin carotenoids, respectively, while these esters were not detected in the food provided.Fig. 1Representative chromatograms 