Dear all,
For those interested in bird vocalisations: we recently published following
paper:
Heij, C.J. and Verboom, W.C. (2005) Spectral analyses of vocalisations of
the Moluccan megapode Eulipoa wallacei (Aves: Megapodiidae) during
egg-laying activities. Deinsea (11), p. 151-157.
Abstract:
Megapode Eulipoa wallacei lives in the tropical hill and mountain forests of
the Molluccan islands and the Papuan island Misool. It is a vocal bird,
especially during egg-laying activities, when it almost constantly utters
sharp cackling ?kek-kek-kek? or ?kuk-kuk-kuk? calls. The same call is heard
in daytime when groups of birds reside in the forests surrounding the
nesting grounds. During observations (1994-1995) of the egg-laying behaviour
on the nesting-grounds of Tandjung Maleo near Kailolo village on the island
Haruku, Moluccas, Indonesia, E. wallacei vocalisations have been recorded.
Spectral analyses of these calls show that spectrograms consist of a
harmonic pattern with increased intensity at frequencies higher than the
fundamental frequency. From that phenomenon it can be concluded that the
spectrogram does not give a full representation of the bird?s vocalisation,
but only show the harmonic pattern of the ?pulse repetition frequency? (PRF
= number of pulses produced per second). It appears that the ?kek? call of
Eulipoa wallacei consists of a series of pulses, of which each pulse has a
fundamental frequency between 2 and 2.5 kHz and a pulse duration between 2.1
and 2.3 milliseconds. The duration of the pulse series itself (one ?kek?) is
highly variable between 40 and 210 ms and the pulse repetition rate within a
?kek? varies between 300 and 650 pulses/second. In general the pulse
repetition pattern is rather symmetrical in time, but irregular patterns are
also possible. The repetition rate of the individual ?kek?s might reflect
the state of aggression, the higher the rate the higher the state of
aggression.
A pdf can be requested from
Wim Verboom
Kees Heij
The Netherlands
|