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Email from Edward van den Bergh:
Hello,
I love the website, thank you for it. On page
http://www.utahbirds.org/featarts/2004/MandarinDuck2.htm the last
picture is of an odd looking Mandarin, which the site suggest may be a
mandarin in eclipse plumage, however, may I propose that it is a rather
more unusual specimen? I think it is a female Mandarin which has
undergone a natural sex-change... this is not what most people
expect, but if one (or both) of the ovaries becomes infected, it is
possible for it to mutate to become a testis, and so to produce the duck
version of testosterone. The plumage then becomes more male, even if the
colours are more female (so grey) since the feather follicles are still
the same and are coded for grey in the egg. They can then actually breed
as males even if they look rather strange. Sounds very odd, but it's
covered in a small book called the mandarin duck by Christopher Lever.
He writes the following:
" a change of sex can occur in many birds, but in the case of the
mandarin duck it is especially obvious because of the elaborate plumage
of the male, which is surpressed by female hormones. In the females of
most birds only the left ovary is functional; if it becomes damaged in
any way ( for example by being shot ) the rudimentary right ovary
sometimes increases in size and acts, not as an ovary, but as a testis,
resulting in a change of sex"
Ducks in eclipse look like this:
With regards,
Edward van den Bergh
Photo in question by Ted Steinke
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