Birds that are active during the day use colorful feathers to communicate, while those active at night have less vibrant appearances and communicate through sound or chemicals. However, some of these nocturnal birds have white patches that can be used for communication if they reflect light. A recent study discovered that the Eurasian woodcock has exceptionally bright white tail feathers that reflect over 30% more light than any other bird, making them ideal for communication in semi-darkness.
Woodcocks can be found in many parts of Europe and Asia, and during the summer breeding season, they inhabit northern regions before seeking warmer weather in the winter. These birds have plump bodies, thin legs, and lengthy beak that makes them skilled at capturing invertebrates for food. They generally reside inland near forest boundaries, and their mottled brown feathers help them blend in with their surroundings. While woodcocks have white patches of feathers on the underside of their tails, these patches are only visible when the bird raises its tail or during courtship displays. Because they are active in low-light conditions, researchers have focused on investigating how these patches can reflect as much light as possible to attract attention.
Using techniques like electron microscopy, optical modeling, and spectrophotometry, the scientists gauged the luminosity of the white patches. They discovered that the feathers reflected 30% more light than any feather previously studied. Remarkably, even compared to birds with famously bright white plumage, such as snowy owls, the woodcocks outshone them all. Feathers consist mainly of a central stem with protuberances called rami, held together by barbules resembling Velcro. In the case of woodcocks, the rami are thicker and flatter, resulting in an enlarged area for reflecting light and a reduced probability of light passing through the barbs without being reflected.
According to the researchers, the thickened rami of the woodcocks' feathers are composed of a network of keratin nanofibers and air pockets that are spread out. This arrangement produces interfaces that can scatter light, which enhances the diffuse reflectance of the feathers. Additionally, the rami and barbules are configured to create a Venetian-blind-like effect that boosts the surface area even more.
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