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@juno.com 92 High Street Mystic, CT. 06355 (860) 572-1717 ____________________________________________________________ Take a break - you deserve it. Click here to find a great vacation. http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTJ3SWIGRp8X2ju87ofp9Kyzrlpv4TTxSgZIZS4lvKWhZqDrUYCJ8k/