>>I don't know much about the Green Magpie, I guess the explanation depends on
>>the degree of colour change experienced during "ill health" and after death.
>> If it is subtle it could be due to whatever yellow pigment is in the
>>feathers. Maybe they rely on a certain plant pigment which is hard to
>>duplicate in captivity?
>>
>That was my guess too but I thought it was interesting that a genus
>(family?) should have switched its 'preference' for making yellow from
>refraction to a pigment.
I thought that fading/loss of refractive colours after death was due to the
physical deterioration of the structures that caused the diffraction in the
first place. This is common also in dead dried insects. As far as fading
in captive birds is concerned, perhaps their refractive structures also get
slightly modified, possibly due to dietry inadequacies, but maybe just from
unhapiness! Sorry, I have no references!
The other aspect of bird colouration that fascinates me is more genetic.
The gene regulation mechanisms that must be in place to produce the range
of age- and sex- related differences let alone the spacial differences over
different parts of the bird's body must be very intricate. As a molecular
biologist with some interest in gene regulation I've thought many times in
the past that it would make an ideal project if funding could be obtained -
unfortunately I haven't been able to come up with much in terms af it being
applied research, and its bloody difficult to get funding for anything
basic!
..........................................
Harvey D. Perkins
Divn Biochemistry & Molecular Biology
Faculty of Science
Australian National University | Editor, Gang-gang (Newsletter of
Canberra, ACT, 0200, Australia | Canberra Ornithologist's Group)
ph: +61.6.249 2663; fax: +61.6.249 0313 | 42 Summerland Circuit
email: | Kambah, ACT, 2902
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