Hi Greg,
Sex chromosomes in birds are different from those in mammals. Male birds
have ZZ chromosomes (compared with XY in mammals) and female birds have
ZW (XX in mammals).
I don't know what happens to a bird's plumage with age, though.
Cheers,
Merrilyn
Greg & Val Clancy wrote:
I banded birds at Iluka Nature Reserve (North Coast NSW) on Monday and Tuesday
with Anthony Overs and others from Canberra. We had two interesting adult
female Golden Whistler recoveries. They were recovered over 12 years 8 months
and over 7 years and 8 months after banding, respectively. The older bird had
very interesting plumage. The belly and lower breast were extensively yellow,
as were the lower belly and vent as is usual for female Golden Whistlers. Its
throat was white mottled grey, similar to adult female but much whiter. The
bird appeared to be partly assuming adult male plumage characters. I have seen
this type of unusual plumage once before many years ago. I was banding with
Bill Lane (at Tumbi Umbi I think) and seem to remember that someone (?John
Disney) told me that it may be due to the degeneration of the gonads which
change the chromosomes from XX to XY and therefore the bird begins to assume
male characteristics. This apparently occurs in the domestic fowl. Does
anyone know if this is true?
Regards
Greg Clancy
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