Article on filoplumes in birds
Who knew that the some of the specialized feathers of birds are actually perceptual organs? This article from the New York Times describes filoplumes, tiny hairlike feathers found at the base of birds’ wing feathers or on their body and that provide them with perceptions essential for control flight and for maintaining body heat. Quoting from the article:
“All birds have filoplumes, even those that cannot fly. There are usually one to three per feather, and they are densest around contour or body feathers and flight feathers.
“Filoplumes detect pressure, touch and vibration in adjacent feathers and, through highly sensitive nerve endings, called Herbst corpuscles, in their follicles, translate those mechanical cues into neuronal signals.
“These sophisticated feathers provide birds with detailed information about their plumage as they fly. They tell them to adjust their feathers to stay warm, or to release heat. They may also detect the movement of parasites, prompting the birds to preen or emit oil in that area. …
“The birds with the most filoplumes are large, strong flying species like eagles, albatrosses and vultures. Albatrosses, which have been known to fly 6,000 miles or more without stopping, are among those who have the most — more than 9,000 have been counted on some birds. So far, red-tail hawks have the most filoplumes per feather among the birds whose feathers have been counted by researchers.”
The article also notes that filoplumes can help birds detect when feathers are broken or cut, so that they can grow the damaged feathers back more quickly.
The article notes that filoplumes have not been much studied, since their perceptual functions were overlooked (perhaps because scientific research on animal behavior has traditionally focused more on physical actions than on perceptions).
Clearly, to achieve their exquisite control of winged flight (doing things far beyond the capability of machines like drones), birds need a lot of channels of perception, including feathery sensors in their wings.