Short-wavelength visual sensitivity and sexual differences in plumage colouration of ovenbirds (Aves: Furnariinae)

Ovenbirds represent a clade of exclusively Neotropical birds that are exceptionally diverse, despite their rather dull, melanin-based plumage. In general, sexes are considered monomorphic in size and colour, but several authors have reported females of some species within this family as being slightly paler than their conspecific counterparts. Our aim was to assess levels of sexual dichromatism in a set of ovenbird species representing a diversity of genera and plumage patterns; Furnarius rufus , Phleocryptes melanops , Synallaxis spixi and Schoeniophylax phryganophilus . For each species, we quantified sexual differences in brightness and colouration among 8–10 different plumage regions through modelling avian perceptual colour-space distances. To best inform our visual modelling parameters, we successfully sequenced the SWS1 gene fragment (associated with short-wavelength, including ultraviolet, visual sensitivity in birds) for one species, P. melanops , and found it possessed an amino acid sequence consistent with the VS-type SWS1 visual system. This provides further evidence supporting the presence of VS-sensitive opsin in ovenbirds. Among all four species, females were consistently brighter than males in at least one plumage patch, but chromatic colour differences between sexes were significant only for the throat patches of Schoeniophylax phryganophilus . Overall, we interpret ovenbirds to exhibit very low levels of sexual dichromatism, manifest mainly by achromatic colour differences.