On Fri, 17 Mar 1995, Stuart MacKay wrote:
> In my experience birds identify predators by shape and posture. Ever seen a
> pigeon swoop over a flock of shorebirds - the effect is dramatic. Same goes
> for crows. I suspect the uniqueness in shape of predators is exactly the cue
> that prey species identify them by.

I find it interesting that some planes will spook birds while others
won't. Maybe this is also a shape thing. Doesn't really matter how low
they are (unless they're *really* low). The wigeons at ML Fill for
instance go crazy when some small planes fly over, but not when others
(I suppose it's a good thing they aren't bothered by large passenger jets,
as they'd have to move elsewhere!). And they certainly don't like the
helicopter that lands near there, which doesn't look like any predator
that I know of. And kites (not the feathered ones) have been know to
disturb birds - so much so they are now illegal at some beaches where
plovers and terns nest.

____________________________
Mike Smith
Univ. of Washington, Seattle
whimbrel at u.washington.edu
http://salmo.cqs.washington.edu/~wagap/mike.html