Thanks Shirley for seeking informed comment from Stephen Debus – very helpful (as one would expect). It does however raise the question (alluded to by Stephen in his response) of whether there really are “pale-plumaged” individuals, implying that there are also darker-plumaged individuals of similar age (rather than them being just fully mature individuals which are intrinsically pale by virtue of their age). Can anyone comment on this?
Does anyone know how I/we might access the article by Paul McDonald referred to by Stephen? (I have been aware of this research and its findings for some years but have not ever read the article.)
Thanks. Richard
From: Stephen Debus
To: Shirley Cook
Cc: Christopher Watson
Sent: Wednesday, October 05, 2011 2:19 PM
Subject: Re: Fw: [Birding-Aus] Brown Falcons with yellow cere and bare facial parts
Hi Shirley & Chris,
Yellow cere is a character of fully adult males, and seems to be particularly prevalent in pale-plumaged individuals (e.g. remote areas like the Centre), perhaps where the falcons live long enough to develop the ‘old male’ characters of yellow cere and eye-ring, and white breast. See: McDonald PG (2003) Variable plumage and bare part colouration in the Brown Falcon, Falco berigora: The influence of age and sex. Emu 103, 21-28.
Cheers,
Steve
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