Haemosporidian parasites and incubation period influence plumage coloration in tanagers (Passeriformes: Thraupidae)

Birds are visually oriented and use their plumage coloration as an
important signaling trait in social communication. Males and females may
have different patterns of plumage coloration, a phenomenon known as
sexual dichromatism. Because males tend to have more complex plumages,
sexual dichromatism is usually attributed to female choice. However,
plumage coloration is partly condition-dependent, therefore other
selective pressures affecting individuals’ success may also drive the
evolution of this trait. Here we used tanagers to study the relationships
between dichromatism and plumage coloration complexity with parasitism by
haemosporidians, investment in reproduction, and life-history traits. We
screened blood samples from 2849 birds belonging to 52 tanager species for
detecting haemosporidian parasites. We used publicly available data for
plumage coloration, bird phylogeny, and life-history traits to run models
with plumage dichromatism and complexity in males and females. We found
that dichromatism was more pronounced in bird species with higher
prevalence of haemosporidian parasites. Lastly, females with high plumage
coloration complexity were associated with a longer incubation period. Our
results indicate an association between haemosporidian parasites and
plumage coloration suggesting that parasites impact mechanisms of both
sexual selections, increasing differences between sexes, and social
(non-sexual) selection, driving females to develop more complex
colorations.