Delayed plumage maturation is linked to body condition, ectoparasite load, and partner’s parental effort in a Neotropical songbird

Abstract

In many bird species, plumage ornamentation plays a crucial role in mate choice by signaling individual quality. Plumage coloration may also signal reproductive success and parental effort, a key driver of offspring recruitment. In a wild population of saffron finches (Sicalis flaveola), a socially monogamous species with delayed plumage maturation in both sexes and biparental care, we captured, monitored, and video-recorded breeding pairs using nest boxes. We examined whether social class (based on age- and sex-dependent plumage coloration) signals body condition and wing ectoparasite load and whether plumage color (yellow or dull) is related to parental effort of paired females and males. We also assessed whether nesting success was associated with post-hatching parental effort and plumage color. Yellow females had better body condition than dull individuals, and yellow birds of both sexes had fewer wing ectoparasites. Males showed greater parental effort when paired with dull females, whereas females tended to invest more when paired with yellow males. Females contributed more to parental care than males, but nesting success was unrelated to plumage class or parental effort. These results suggest that yellow plumage in saffron finches signals female body condition and wing ectoparasite load in both sexes and may influence parental investment by mates.