Feather iridescence of Coeligena hummingbird species varies due to differently organized barbs and barbules

Hummingbirds are perhaps the most exquisite bird species because of their
prominent iridescence, created by stacks of melanosomes in the feather
barbules. The feather colours crucially depend on the nanoscopic
dimensions of the melanosome, and the displayed iridescence can distinctly
vary, dependent on the spatial organization of the barbs and barbules. We
have taken the genus Coeligena as a model group, with
species having feathers that strongly vary in their spatial reflection
properties. We studied the feather morphology and the optical
characteristics. We found that the coloration
of Coeligena hummingbirds depends on both the
Venetian-blind-like arrangement of the barbules and the V-shaped, angular
arrangement of the barbules at opposite sides of the barbs. Both the
nanoscopic and microscopic organization of the hummingbird feather
components determine the bird’s macroscopical appearance.