Data from: Multiscale physicochemical characterization of melanin-based feather coloration in the rapid Capuchino Seedeater radiation

Melanin-based plumage coloration in birds is shaped by pigment composition
as well as melanosome morphology and distribution; however, the ways in
which these factors together modulate observable color remain poorly
understood. We investigate this relationship in the Capuchino Seedeaters
(genus Sporophila), whose recent, rapid radiation driven by sexual
selection resulted in 12 species with diverse coloration patterns. Using
scanning electron microscopy (SEM) and micro-computed tomography (µCT),
combined with a novel application of Fontana-Masson stain to image
melanosomes at high resolution, we characterize melanosome distribution
and morphology in several variably colored plumage patches across
Capuchino species. Melanosome morphologies followed patch-specific
patterns that did not directly correlate with coloration: crown feather
melanosomes were larger, more elongated, and had greater percent eumelanin
content than those in belly, throat, or dorsum/rump patches. We also
observed that dorsal patches had more total melanin than ventral ones,
with pigment and coloration patterns suggesting possible signaling and
photoprotective roles. More generally, we show how the patch-specific
coloration of male Capuchinos is accompanied by differences in melanosome
morphology and melanin composition and abundance. Our work highlights the
challenges that remain in understanding how the nanoscale mechanisms of
melanin-based pigmentation translate into macroscale plumage coloration.