Bill Daniels wrote:
It's pretty well established that soaring birds have extremely good
eyesight. I think they just see the ground moving away when they are
climbing.
Good eyesight is one thing, precision at judging distance another,
the latter basically dependent on how far apart your eyes are.
No way can they judge their climb rate based on seeing the ground
moving away.
Thermals also have a lot of stuff in them like insects and seeds.
The birds are probably able to see these rising at a considerable distance
That could be, and other visual cues as well.
CV
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