This is the dilemma, Des.
Birds commonly go from green to blue because of loss of carotenoids, or
green to yellow because of loss of structural blue. If this is the
mechanism in this case the red female, if carotenoid dependent should have
gone from red to black. Instead she went from red to yellow. This suggests
that carotenoids were not wiped out. Even if the colour change was due to
porphyins, loss of which could account for loss of both red and green, then
the female should have been left with a black background if there were no
carotenoids, or green if the carotenoids were inter-playing with a
structural blue back ground.
We could account for the changes if the female had a black background and
carotenoids altered from red to yellow and the male had a blue background
and lost carotenoids completely. However, it's hard to imagine that the
same mechanism that wipes out carotenoids or porphrins in the male could at
the same time allow carotenoids to be expressed in the female.
I wish the birds would read the text books! Anyone else willing to have a
shot at the puzzle?
Pat Macwhirter
>I'm no expert but I know that Asian Green Magpies kept in captivity go
>blue, presumably because of a lack of carotenoids in their diet.
>
>Des Allen
>
>Tokyo
>
>At 8:57 PM 98.5.8 +1000, Pat Macwhirter wrote:
>>Hi all,
>>
>>We've been kicking around a case on the Birdmed list with which we were
>>wondering whether any Birding-aus people might be able to help.
>>
>>Eclectus clutch mates both showed stress lines of colour change, the hen
>>(sorry about the avi-jargon) going from visual red to yellow while the cock
>>went from visual green to blue. What the debate is about is a common
>>physiological insult which would allow for these colour changes.
>>
>>Is there anyone on Birding-aus who has done work on feather colour and
>>could offer an explanation based on the interplay of porphyrins (green and
>>red), carotenoids (yellow and reds), eumelanin and phacomelanin and
>>structural blue (etc) that would logically account for these changes. Does
>>anyone have information as to whether visual red in Eclectus hens is due to
>>porphyrins or carotenoids and/or whether green in the males is due to
>>porphyrins or combination of structural blue and carotenoid yellow?
>>
>>Pat Macwhirter
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