White-tailed Goldfinch

Does this goldfinch look odd to you?
I know goldfinches’ tails are white with black terminal markings, but this one seems to have a lot of white. I keep waffling back and forth on whether I’m overreacting by calling him leucistic (a genetic mutation that causes melanin pigments to become washed out and pale) or if there is a more prosaic explanation.
Still, I’ve watched hundreds, if not thousands, of goldfinches at feeders over the years and this bird stands out, so I don’t think I’m making something from nothing. This bird’s tail is abnormally white.
The yellow on the rump is normally more pronounced but it’s faded and hard to see here. The black areas at the end of the tail are usually more extensive as well. This missing black is the real reason the tail looks so damned white to me.
Compare his tail with this one from a “typical” goldfinch.
This one has more black, but it’s hard to say for sure because the wings cover a significant part of the tail when folded back like that.
So, let’s break this down:
  • The bird in question is molting (look at his forehead.) My first thought was that the molting process was causing the tail to look so white. But once I learned that goldfinches don’t replace their wing or tail feathers during their spring molt, I tossed that hypothesis.
  • Our bird also holds his wings in a very loose, drooping posture, where most goldfinches keep them folded across the back, In fact, I couldn’t find a single photo of a goldfinch holding its wings in this way. But even in in-flight photos, with the tail exposed, none have tails that look that white. This posture does allow more of the white part of the tail to be seen. But that doesn’t account for the reduced black at the end of the tail.
  • That brings us to the possibility of leucism. All the leucistic goldfinches I’ve found online have been affected over a larger area of the body, usually from the neck down, but including the head on occasion. I did, however, find one account of a bird with a white patch on the top of his head and no other abnormal coloring. I also found other species of birds with leucism that only had white tails and they looked similar to what we have here.
  • According to Feederwatch, occasionally a bird will lose feathers in a close call with a predator. When this happens the new feathers sometimes grow in white and then change back to the normal color at the next regular molt. This kind of white coloring looks like leucism but is not and most often happens in the tail, causing a bird that lost its tail feathers to a predator to have an all white tail. that’s not the case here since our bird doesn’t have an all white tail, instead still having black in reduced amounts.
So where does that leave us? Despite the fact that leucism isn’t that common—Feederwatch has recorded 1600 cases from 5.5 million birds—I believe this bird is partially leucistic. Unless I’m missing something, the evidence seems to point in this direction. If any of my half-dozen readers (you can’t hide, I know you’re out there) have another take, I’d be thrilled to hear from you.



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