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From: "Ronald Orenstein" <ornstn@home.com>
Sent: Wednesday, February 28, 2001 11:47 PM

> echolocating birds use a lower (audible) frequency which I gather is less
> precise at object discrimination and does not have the added property of
> being able to "jam" insect hearing systems).

Steatornis use extremely basic clicks to "echolocate", as does the megabat
genus Rousettus, which probably only return basic information about
proximity to large surfaces like walls. They show none of the adaptability
of echolocation calls used by microbats, but you can perhaps see how they
got there.

The "jamming" is normally done by the insect, by the way - they emit clicks
which confuse bat echolocation systems. Insects, however, will react to bat
echolocation signals - first by orientating away from the sounce of pulses,
and then by falling out of the air. Most bats can predict or react to this
and intercept the falling insect. Steatornis clicks could, if they went high
enough in frequency, have the same effect on insects, but I don't know what
their bandwidth is. Probably not high enough. You can disable noctuid moths
by jangling a bunch of keys together, to give you some idea of how
generalised the response is, but it almost certainly evolved in response to
bat echolocation.