Plumage colour of Blue-capped Manakin males predicts female visitation rates but does not signal avian haemosporidian infection

Abstract

Colourful plumages may bear high production and maintenance costs. The parasite hypothesis posits that visual signals work as honest indicators of heritable resistance to parasites. However, the value of structural and melanin-based colours as honest signals is still an open question awaiting evidence, especially in lekking species, for which sexual selection is supposedly more intense than in socially monogamous species. In this context, we sampled 24 adult male and 26 adult female Blue-capped Manakins (Lepidothrix coronata) from a population in central Amazonia to test the hypothesis that (i) plumage colour of male Blue-capped Manakins influences the attraction of female individuals; and (ii) the occurrence of haemosporidian parasites is associated with the plumage colouration patterns of Blue-capped Manakin. We estimated the frequency of female visits at individual perches of Blue-capped Manakin males through behavioural observations, measured colour spectra from eight plumage patches of male and female individuals, and examined whether these individuals were infected with haemosporidian parasites using molecular screening techniques. We found that variation in melanin-based pigment and structural colours amongst male Blue-capped Manakin was associated with female visits. However, variation in these colours did not correspond to the occurrence of haemosporidian parasites. In contrast to previous studies, we suggest that the structural and melanin-based colouration of male and female Blue-capped Manakin may not be costly enough to be used as an honest signal of susceptibility to haemosporidian parasites.