A picture would help.

Sorry about that, I thought I posted a picture but it didn't work for some reason, I'll try again.

My first (and only) guess is a leucistic robin. I have a leucistic Northern Cardinal that frequents my feeder and first look at your bird made me think that it is leucistic. Have a look at the link below and also use Google Images for 'leucistic robin'. They are rare, but it happens.

Kindly,
Jane

Here is a link that might be useful: Cornell University

I agree that the bird appears leucistic, but I don't think it is a robin. Since a robin's wings are normally black, the pigment in a robbin's wings would be melanin, which could appear as a light gray, not yellow. Yellow pigment would be caused by carotenoids. So a normally red breast may only have enough carotenoids to appear yellow. Of course, there can be areas with no pigment at all that will appear white. Wish I knew what kind of bird that is, but I can't tell.

After doing a bit of research on leucistic birds, I believe it is most likely a leucistic sparrow, as it was traveling with some other sparrows. I've attached another picture showing it with the other birds.
I didn't realize what a rare sight this was, I wish I had taken better photos.

Good catch on the leucistic sparrow. I agree that it is most likely a sparrow just by who he/she is hanging around with. Also robins don't usually eat black oil sunflower seeds (BOSS). I've been a mostly backyard birder for about 45 years and have seen 1 totally albino robin, 2 or 3 leucistic robins, 3 leucistic house finches and 1 either leucistic wild turkey or he may have been a mix with a domestic turkey-he was gorgeous!
Susan

At least one of those other birds looks like a redpoll - the one on the upper right seems to have the red cap. That said, I don't know what your leucistic bird is - I hope someone can identify it.

Claire

I just found a pic of a leucistic pine siskin which shows a little yellow on its wing. Your first pic also shows some yellow so maybe it's a pine siskin.

This post was edited by claire on Wed, Jan 9, 13 at 18:34

After Claire posted , I looked more carefully & it looks like that upper right bird could be a redpoll! So now I don't know what your mystery bird is. Hopefully a more knowledgeable (sp?) birder will come along to help.Birdingnut? At least we know it eats BOSS, so that may help a bit.
Susan