Carotenoid-based plumage pigmentation and concentration as a function of sex and habitat type in the Yellow-breasted Boubou Laniarius atroflavus
The study of avian integumentary colouration can offer insight into dietary and metabolic processes as well as fitness in focal species. Yet, we know relatively less about the system of feather colouration in African birds in comparison to Europe, North America and the neotropics. In this study, we biochemically characterised and quantified the pigmentary basis for breast plumage colouration in the Yellow-breasted Boubou Laniarius atroflavus, a little-known Afromontane species restricted to the Nigerian–Cameroon Highlands. We also measured differences in carotenoid concentration and feather reflectance between sexes, and between birds inhabiting edge and riparian habitats. Six carotenoid pigments were recovered from the yellow feathers – canary xanthophyll A and B, a cis isomer of each, isoastaxanthin and an unidentified carotenoid. We determined that the yellow colour of the breast feathers is carotenoid-based, with the greater proportion as canary xanthophylls. The presence of the ketocarotenoid, isoastaxanthin, provides the basis for further studies into red, orange and yellow coloured congenerics. Males appeared to have higher feather pigment concentrations than females, and birds resident in the edge habitat appeared to have slightly higher feather pigment concentrations than those in the degraded riparian habitat. There was little indication of differences in feather reflectance between sexes and habitat types. However, low samples size restricted further differentiation. There is also the need for further studies on the dietary and metabolic pathways of feather colouration to better understand how ecological variation may shape pigment uptake, transport, synthesis and deposition in feathers.