Patty:

I haven't kept up with this topic for awhile, but here are some older
references. In general, color changes are controlled by hormones: androgens
in some species (eg. House Sparrow, European Starling), estrogens in the
Quelea, and luteinizing hormone (LH) in the Paradise Wydah.

Mundinger, P.C. 1972. Annual testicular cycle and bill color change in
the eastern American Goldfinch. Auk 89:403-419.

Witschi, E. 1961. Sex and secondary sexual characters. Pp.115-168 in
Biology and Comparative Physiology of Birds. (A.J. Marshall, ed.) Vol. 2.
[This gives an excellent summary of the research that had been done up
until that time.]

Wydoski, R.S. 1964. Seasonal changes in the color of Starling bills. Auk
81: 542-550.


Dick Johnson
Conner Museum and Dept. of Zoology
Washington State University
Pullman, WA
johnsonre at wsu.edu




>Oops! I geuss I should have phrased my question differently. I have gotten a
>few responses to my query, but none that answered the question I
>THOUGHT I was asking. My mistake! The question I have is not what the
>different appearences of bill color ARE, but what causes them to change color
>or pattern?
>
>Thanks again!
>
>Patty
>
>Patty Gates
>Capitol Hill
>Seattle, Wa
>(javajunco at netscape.net)
>
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