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300199.  Sat Mar 22, 2008 6:30 am Reply with quote

Birds’ main sense in sight (as is humans’). Their eyes are fairly similar to ours, but much bigger in proportion to head size. If our eyes were proportionally the same, they’d be roughly the size of apples.

However, it is no longer believed that birds have dramatically superior eyesight to humans. They are not “eagle-eyed”. Some of the findings are astonishing, considering what we all thought we knew ...

Humans can see in the dark as well as tawny owls can; it is the owl’s combination of good eyesight and excellent hearing that allows it to hunt so well in darkness.

Eagles can’t see 10 times as much detail as we can - it’s 2 or 3 times, at most. The “overall ability to see detail” of humans and birds is “surprisingly similar”.

Birds do have an extra muscle in the eye which allows them to focus their eyes faster than we can.

The big difference between human and avian eyes is positioning, of course; our front-placed eyes mean we can see about 60 degrees field of vision, whereas birds have 360 degrees. A woodcock or a snipe has eyes high on the side of the head, which means it can see “virtually 360 degrees in the horizontal plane” and binocular vision ahead and behind. In other words, these birds can see in front and behind and over the entire horizon all at the same time.

Birds can see more types of light than we can; recent research also suggests that some birds can see magnetic field lines, and use them for navigation.

S: Birds magazine, Aug 07.

300204.  Sat Mar 22, 2008 6:39 am Reply with quote

Well that's certainly surprising if true. Does it say how (eg) hovering kestrels spot small prey animals in the undergrowth? I think I recall something about being able to see urine trails in the ultraviolet spectrum, so maybe that's it.

300216.  Sat Mar 22, 2008 7:13 am Reply with quote

No, I wondered the same; it doesn't go into it. But I assume it's as reliable a source as could be had for such matters, since it's the RSPB's official organ.


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