New research led by Imperial College London suggests that Eurasian woodcocks (Scolopax rusticola) have evolved their bright white feather patches for long-range visual communication in dimly lit environments.
Diurnal birds (most active during the day) often have colorful plumages, which they use to communicate information with each other.
Birds that are most active at dawn and dusk or at night (crepuscular), such as nightjars and woodcocks, tend to have less showy plumage, as while sleeping during the day they need to be camouflaged to avoid predators.
Rather than using showy plumages, it was thought that birds active during low light conditions instead used sounds or chemicals to communicate.
However, many have bright white patches, which could be used in environments with very little natural light for communication if these are reflective enough.
“Until recently, and when compared with diurnal birds that use contrasting plumage patches and complex feather structures to convey visual information, communication in nocturnal and crepuscular species was considered to follow acoustic and chemical channels,” said Imperial College London researcher Jamie Dunnin and colleagues.
“However, many birds that are active in low-light environments have evolved intensely white plumage patches within otherwise inconspicuous plumages.”
Eurasian woodcocks are primarily mottled brown, but have patches of white feathers on the underside of the tail.
This means the birds only show these patches when raising their tail or during courtship display flights.
However, as they are crepuscular, and so most active during low light, these white patches need to reflect as much light as possible to attract attention.
To investigate how they might do this, the researchers examined the white tail feathers of Eurasian woodcock specimens from a collection in Switzerland.
They used specialised microscopy to image feather structure, spectrophotometry to measure the light reflectance, and…
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