03-21-2003, 02:56 PM
When the wind gets up to about 30 miles per hour, or when riding a motorcycle above that speed, a person need glasses to protect their eyes. How can birds fly at that speed and more and not get their eyes irritated?
03-21-2003, 03:36 PM
I was going to say something about most not flying that fast, and then I found this (http://newton.dep.anl.gov/natbltn/200-299/nb215.htm) :[ QUOTE ]
The world's record for speed among living things Is best established for
the Indian spine-tailed swift, a bird which was repeatedly clocked In
level flight, over a carefully measured two-mile course, in as little as
3Z.8 seconds or 219 Mlles an hour. The European peregrine, a hawk
used in falconry, was timed at 165 to 180 mph during its dive after
quarry. In the United States, the golden eagle and the duck hawk can
dive from high altitudes at similar speeds and the latter, In level flight,
easily overtakes and seizes such swift birds as ducks and pigeons.
A few homing pigeons have averaged 60 mph over courses of a few
miles and as much as 55 mph for 4 hours. The mourning dove and the
golden plover have been chased by airplanes at 60 to 65 mph. Some
ducks and geese can reach speeds of 55 to 60 mph or more, and the tiny
hummingbird can do 50 to 55. Most birds habitually fly at speeds much
less than their maximum. For example, crows commonly cruise at 20 to
30 mph but can speed up to 40 or 50. The distance endurance record is
thought to be held by the Arctic tern which migrates to the Antarctic
and back in about 20 weeks a distance of 20,000 to 22,000 miles.<hr /></blockquote>So, I'm going to hazard a few guesses: 1) Their eyes are on the sides of their heads (most birds), and aren't as subject to FOD (Foreign Object Damage), 2) Possibly, avian corneas are much tougher--I'll see if I can find any evidence for this (Is there an ornithologist in the house?), and 3) With the exception of take-off and landing, I would imagine there is less debris that is airborne at common flight altitudes.
Like I said, just guesses. . . .
BTW, I used to run visor up on my 'cycle, usually without even squinting, until about 45mph. Higher than that, and the wind would irritate my eyes, so then I'd drop the visor for protection.
Edit: I just found that some birds have specialized feathers called "bristles" [ QUOTE ]
Bristles: vaneless contour feathers, found mainly on the head. Function varies among species and <font color="red">is not well known in some cases (e.g., the rictal bristles around the mouths of aerial insectivores which seem to play a role in eye protection;</font color> note that these bristles appear not to be used as "insect catching nets" as has been hypothesized). <hr /></blockquote>
Powered by vBulletin® Version 4.2.0 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.