It may come as a surprise that the brown and largely nocturnal Eurasian Woodcock sports the brightest known feather of any species.
Better known for its cryptic plumage, which makes Eurasian Woodcock all but impossible to see on the woodland floor, it is the tips of the bird's tail feathers which intrigued researchers.
Rarely noticed, the white tips to Eurasian Woodcock tail feathers are brighter than the plumage of Snowy Owl and Arctic Redpoll (Helge Sorensen).
In a new pre-print (submitted for publication) into the mechanisms responsible for the brilliant white tail feather tips, seldom seen in the field, the team led by Jamie Dunning of Imperial College London discovered that they reflect around 30% more light than the next brightest feather measured, which belongs to Caspian Tern.
The reverse surface of the white Eurasian Woodcock fail feather tips reflected around 55% of light, as measured using spectrophotometry. This is around five times brighter than Snowy Owl and 10 times brighter than the feathers of Arctic Redpoll, both known for their startling white plumage.
Scanning and transmission electron microscopes were used to examine the nanostructure of woodcock tail feathers. These observations revealed that the strong reflection of light, pipping diurnal contenders for the brightest white in the bird world, is achieved by incoherent light scattering by the keratin and air within each feather barb.
It is thought the white in the plumage has evolved for visual communication at dusk and on the dimly lit woodland floor (Marc Fasol).
The effect is intensified by the overall flat and thick shape of each barb, and how they arrange like a 'Venetian blind' to maximise the surface area reflecting light.
The authors suggest that woodcocks may have evolved the intensely reflective feather tips to communicate with each other in the dim light of the woodland floor, and during crepuscular flights. All eight of the world's woodcock species have white patches in their tail feathers, but these have not all been specifically measured.
Reference
Dunning, J, Patil, A, & 6 others. 2022. How woodcocks produce the most brilliant white plumage patches among the birds. bioRxiv. DOI:
