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. 

We have screened 4234 individuals from 53 species (all belonging to the Thraupidae family) for the presence of hemosporidian parasites (Order Haemosporidae, genera Plasmodium and Parahaemoproteus). First, we performed PCR to identify the status of infection of each individual by amplyfing a barcode region of the cytochrome b. We then used BIOEDIT v.7.2.0 to alling sequences and compare them with the MalAvi database. Finally, we used the number of lineages and weighted it by the number of captures per species as our variable "lineage richness". The haemosporidian parasite prevalence (Plasmodium and Parahaemoproteus) was the number of infected individuals divided by the total capture individuals as well.

All analysis can be performed in the R software.