The Wikipedia extract (quoted by rchapanis" < Tue,
15 Apr 2008) is perhaps a little misleading in the statement:
"The lyrebird's syrinx is the most complexly-muscled of the Passerines
(songbirds), ..."
I quote from The Directory of Australian Birds, Schodde & Mason (CSIRO
Publishing, 1999). Referring to lyrebirds (page 60):
The other feature is the structure of the syrinx which is tracheo-bronchial
with free rings but otherwise oscinine-like except for its three instead of
the usual four intrinsic muscles.
"complexly-muscled" is hardly consistent with having fewer muscles.
Regarding mimicry, it is important to distinguish between breeding season
vocalisations and sounds made by lyrebirds at other times of the year. In
the wild, breeding season mimicry does not include mechanical sounds of
human origin. There is little doubt that they can faithfully reproduce
almost any sound they hear, and away from the breeding season (winter) they
may copy mechanical sounds but only very rarely indeed.
A remarkable 'mechanical' sound, (not of human origin), which both species
produce with the voice as part of their breeding season song, is a perfect
imitation of the sound of feathered wings.
In the wild, young male lyrebirds learn to sing by copying adults. (They
take about 7 years to reach maturity.) The Superb Lyrebirds' complex
breeding season repertoire of their own and mimicked calls is culturally
transmitted down the generations. This is shown by the population in
Tasmania where they were introduced some 60 years ago. For a number of
decades they retained mimicry of two species of birds that do not occur in
Tasmania.
Cultural transmission is demonstrated even more strongly by the other
species, the Albert's Lyrebird. In the breeding season, they use their
mimicry to form a complex song some 40 or 50 seconds long, in which all the
sounds come in fixed order; and all the males in any one population use the
same mimicry cycle. This may be cycled over and over by the performing
bird. Populations in different areas have different cyclic songs, though
all have a large component of mimicry of a variety of the strange sounds
made by Satin Bowerbirds. (And in passing, I have one recording where a
male gave 121 cycles of his sequential song over a period of 1 hour 42
minutes. The song is aimed at attracting the female for mating. He was
successful!)
In captivity, if an immature male cannot hear other lyrebirds, he must
perforce copy those sounds that he does regularly hear. Hence, for
example, the mimicked camera shutter and camera-wind sounds in an
Attenborough film.
Cheers
Syd C (in Brisbane, Australia)
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