[CT Birds] Siskins

brushes2 at juno.com brushes2 at juno.com
Thu Mar 5 08:26:58 EST 2009


Birders,

Here's what these green birds look like to me. First, I've seen only the
photos posted here, some of which are quite good. However, there is
nothing like the bird in hand. It would be informative to tease out the
individual feathers involved for visual inspection.

All the 'green feathers' on the siskins remind me of the henny feathers
in something like female scarlet tanagers. Same in other birds where a
yellow pigment is mixed with melanin. This combination often produces a
green. It's like mixing yellow and blue to get green in watercolors. It
is most likely that the yellow pigment is a carotenoid. That being the
case, it is dietary in origin and deposited in the feathers as they grow.

I have no idea what causes these individuals to appear green. It's not
likely to be an 'excess' of yellow that 'spills over' into neighboring
feathers that normally don't contain yellow pigment. Since I don't know
if this appears in these feathers all through the year or not, it's hard
to say which molt it might associated with. It may or may not be
seasonal. With out knowing the sex of the birds, you can't tell if it is
related to the alternative plumage or a character of the basic plumage.
Studying a long series of museum skin, with dates and sex, would be
helpful.

Short of that type of information, it is speculation to say much more. In
the long run is could simply be individual variation that occurs in this
flock. We really have no idea if these individuals were together when
they moulted into the basic plumage, presumably prior to the winter
movements south.

Cheers,

Alan


Alan H Brush
brushes2 at juno.com
92 High Street
Mystic, CT. 06355
(860) 572-1717
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