Data from: Inter- and intraindividual variation in the feather coloration of American crows

Avian feathers are remarkably diverse in both form and function.
Coloration is among the most studied features of feathers, but we know
relatively little about melanin-based black coloration. Despite many crows
(Corvus sp.) and other corvids having black feathers that appear uniform
to human perception, their feather coloration could play an important role
in social communication. We therefore tested whether the
coloration of American crow (Corvus brachyrhynchos) feathers varied by age
class and sex, two socially-relevant variables. Using a visual modeling
approach that accounts for the visual system of American crows, we
measured the coloration of American crow feathers from museum specimens.
We found that feather coloration varied by age class but not sex. Older
individuals had feathers with a different hue and more ultraviolet than
younger crows. Discriminant function analyses correctly categorized
individuals into age classes based on feather coloration with high
classification success. The coloration of American crow feathers did not
vary based on the time since the last molt and replacement, but did vary
with the time since the specimen was collected. The visual modelling
approach suggests that crows can discriminate among different feather
regions. One region with particularly distinctive coloration properties
was a facial mask, which could potentially function to minimize eye glare.
Our results suggest that feather coloration in American crows (and
potentially other seemingly monomorphic corvids) could reflect underlying
qualities of those individuals that are important for social
communication. Associated data in the manuscript is provided.