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During
our holidays we found that a pair of barn owls were
roosting in a building close to our house. This gave
us a grandstand view every evening as they emerged and
flew off into the gathering darkness for the night's
hunting. I had located the roost by finding a flight
feather on the floor of the building. I have always
wanted a close look at an owl's wing feather. By
holding it flat and level with my eye, I could see
that the vane had a velvety surface, unlike the
shining smooth surface of a normal wing feather
(admittedly not easy to see in my photo).
The velvet texture serves to
deaden the noise of the owl's wing beats. Even small
birds produce a noisy whirring in flight, but owls
produce no more than a quiet whisper as they quarter
the ground. Their prey is mice and voles that rely on
acute hearing to warn them of approaching danger.
The
concept of this feather structure is the same as the
oars muffled with cloth wrappings once used by sailors
on clandestine expeditions. The drawback is that the
soft texture increases the drag of air flowing over
the wings and makes flight more strenuous. It comes as
no surprise, then, to find that those owl species,
such as hawk owls and fishing owls, that habitually
hunt by day, when silent flight is not important, have
normal, smooth wing feathers.
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