Female Golden Whistlers

To: "Birding-aus" <>
Subject: Female Golden Whistlers
From: "Greg & Val Clancy" <>
Date: Sun, 10 May 2009 14:04:01 +1000
I received the following from Win Filewood:

"I've read/heard something similar about Golden & also Rufous Whistler. As I 
understand it birds are opposite to mammals in sex chromosome patterns : males 
are the equivalent of mammalian females (XX) & females of course the opposite. 
I understand that avian geneticists prefer the notation WW/WZ for males/females 
to avoid confusion in ignorant theriocentric (mammal-dominated) folk. This is 
one explanation why there is an excess of males in many bird species - females 
are more likely to have sex-linked disabilities equivalent to human haemophilia 
or red-green colour-blindness. However a recent astonishing finding is that 
female birds (at least of some species) can actually control the sex of their 
offspring to some degree. How, I know not, if anyone yet does.
I can't see how the actual chromosome pattern of a bird could change during its 
lifetime. In mammals, both sexes produce the same sex-hormones, just in 
different proportions. The Y-chromosome carries very few functional genes but 
one is the testosterone-making main switch. However females also produce some 
anyway, and there are plenty of "gender-confused" folk out there to show that 
proportions not only differ in time in any indivual, but also bewteen 
individuals. I suspect that some such mechanism, involving a gradual weakening 
of estrogen production, and/or strenthening of male hormone production, is the 
cause of masculinization in whistlers over time. If in fact it really happens. 
I think it does - we should look at Shrike-thrushes too, but throughout HANZAB 
& other plumage description refererences, the phrase 
"brighter/more-extensive/&c in OLDER FEMALES" is often used. Yet this might be 
circular - brighter females may be assumed (by mammalian chauvinists) to be 
Lots of food for thought from a single band-recovery! And people ask me why I 
do it."

Greg Clancy

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