RE: bird vocalisations

[(Andrew Taylor)]

I highly recommend Welty's "The Life of Birds" as a general reference on
birds.  Its an undergraduate text.

It gives a couple of examples of differential alarm calls including the
European Chaffinch which gives a very different call for a flying
predator to a static predator and domestic fowl which has different
calls for ground-based predators and flying ones.   Over 20 species
have shown to respond to Chaffinch alarm calls.  The Chaffinch call
for a static predator, because of it acoustic characteristics, make
it easy to determine the callers direction which may assist in the
formation of mobbing groups.  The flying predator call is such that
the caller is difficult to locate.

I'm sure I've read of work showing convergence between species of
alarm calls.

Andrew Taylor