Don Nelson writes:
>
> The last few sunny mornings as I left for work, I heard an unusual bird
> singing from the branches of our birch tree. "A sparrow," I thought, "but
> a new one to me!" The binos revealed a song sparrow curiously distorting
> a song sparrow song: my impression was that it was a brave attempt at
> song by a young male who hadn't quite got all the trills and glissando's yet.
>
> Do birds 'grow into' their mature voice and complexity of song?

Yes, definitely.
I'll take as a nexample a bird very familiar to me (probably not for most
of you), the Chaffinch _Fringilla coelebs_.

In this species, as in many others *I think*, reproductive "paraphernalia"
(this includes testes and vocal apparatus), which represents an important part
(well, many percent) of the breeding bird's weight, is reduced in winter to a
few tenth of a percent.
In late winter/early spring, the guys have to regrow all the stuff again...
In particular, their vocal apparatus being regrowing, you can imagine that they
don't really sing "right" (usually much shorter phrases ending *very* weirdly)
until the full regrowth.


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The Comet cometh, Gromit gromith.
Serge Le Huitouze Intelligent Software Group
email: serge at cs.sfu.ca School of Computing Science
tel: (604) 291-5423 Simon Fraser University
fax: (604) 291-3045 Burnaby, B.C., V5A 1S6 CANADA