Revisiting the condition-dependence of melanin-based plumage.

Support against the condition-dependence of melanin plumage signals has relied on data from species exhibiting both melanin- and carotenoid-based plumage ornaments. As the mechanisms leading to variation in carotenoid- and melanin-based plumage differ fundamentally, these systems may not be ideal to assess the condition-dependence of melanin signals. Instead, we hypothesized that melanin-plumage is more likely to signal condition in purely achromatic species. We performed a meta-analysis reviewing evidence for condition-dependent melanic plumage: we compared the net effect size for the relationship between melanin traits and condition in species that are achromatic versus species that also display a carotenoid-based trait. Our results indicate that melanin plumage is condition-dependent in species of both plumage types. Contrarily to our prediction, this finding suggests that melanin ornament condition-dependence is not conditional on the context of other ornaments within a species. Instead, melanin ornaments should be viewed as potential condition-dependent signals in all species. [ABSTRACT FROM AUTHOR]