This is not quite what Ralph Reid was referring to when he asked (Oct 15)
"Were the magpie's alarm calls an example of a 'common threat warning'
shared by the different species?". He had two magpies screaming in a small
eucalypt.
However, it does refer to similarity of alarm calls in a number of species,
and may be of some interest.
In "Bird Song - Biological themes and variations" by C. K. Catchpole & P. J.
B. Slater, Cambridge University Press, (at page 88 in my 1995 copy) under
the sub-heading of "Localisation of bird calls", the authors write:
"These various possibilities for auditory localisation were first
discussed in relation to bird sounds by Marler (1955). He suggested that
the 'seeep', an alarm call produced in almost identical form by a variety of
European passerines (see Fig. 4.7) had converged on that form in different
species because it was ideal to avoid localisation. Producing a call in the
presence of a predator such as a hawk is a risky business, and selection
might be expected to minimise that risk."
I think that (unfortunately) I cannot reproduce that Fig. 4.7 in this
posting. It shows audiographs of the alarm calls of the Reed Bunting,
Blackbird, Great tit, Blue tit and Chaffinch. They are all remarkably
similar, and it is reasonable to expect that an alarm call from any one of
them would be recognised by all of them as indicating an alarm situation.
Cheers
Syd
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