As an aside, in the 1970s in Western Australia, Ian Rooke (Uni of Western
Australia) and Terry Knight (CSIRO) examined alarm calls of New Holland,
White-plumed and White-naped Honeyeaters. They found that specialised
ear-feathers were probably acting as pinna, assisting the honeyeaters to
better perceive the directions, locations and intensity of sounds. The
intensity and volume of the alarm call of individual honeyeaters are higher
the closer the predator is to them. Therefore, if an aerial predator flies
over a flock of honeyeaters, individuals can determine how close the
predator is to them and the direction it is flying over the flock by
listening to the intensity and volume of alarm calls of conspecifics in
their immediate area.
Stephen Ambrose
Ryde NSW
Reference:
Rooke, I.J. & Knight, T.A. (1977). Alarm calls of honeyeaters with
reference to locating sources of sound. Emu 77: 193-198.
Abstract
The alarm calls that are given in response to a flying hawk by the New
Holland Honeyeater Phylidonyris novaehollandiae, the White-plumed Honeyeater
Lichenostomus penicillatus and the White-naped Honeyeater Melithreptus
lunatus are described. Animals locate sources of sound by comparing
differences in intensity, phase and timing cues of the incident sound at
each ear. These processes are explained and previous explanation is
criticized. Some animals create more directional cues from incident sound
with pinna. The structure of the alarm calls of honeyeaters makes them easy
to locate and some honeyeaters possess specialized ear-feathers that may
function as pinna. The function of the alarm calls is discussed with
reference to survival value.
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