A Fancy Goldfinch

Yesterday afternoon I went for a walk and ran into a mixed feeding flock of chickadees, goldfinches, siskins, and redpolls working their way through a stand of hemlock trees. It was the first time I’d seen redpolls out in the woods rather than at a feeder, so I stopped to watch them for a bit. Eventually, though, it was one of the goldfinches that really caught my eye.

American Goldfinches (Spinus tristis) are sexually dimorphic in the summer, meaning the males and females look different – in this case, the males are bright yellow with a black cap while the females are drab olive. For winter, however, the males molt into olive-drab plumage of their own and are usually almost indistinguishable from their ladies. What I spotted yesterday was a goldfinch that seemed to defy this rule. Here we are in December and he (?) still had a bright yellow face.

This photo from Wikimedia Commons by Dick Daniels was taken in February and shows a male starting to transition back to his spring plumage. The one I saw had a brighter face than this – and in December.

I can tell you how and why the males change color – the lemon-yellow color in their feathers comes from pigments in their food called carotenoids. It helps the males attract females, who know that a brightly-colored male must be getting a high-quality diet and might have good genes to pass on to her offspring. In the winter, when they’re not breeding, males presumably switch to a less conspicuous color in order to avoid predators.

What I don’t know is why some males actually keep varying amounts of their yellow color through the winter (and some don’t). In fact, if you pay attention to the goldfinches coming and going from your feeder you can even pick out individuals based on how much yellow they retain and where it on their bodies it is. Does this have something to do with age? Diet? Hormones? Beats me, and I haven’t been able to find any answers online, either.

I’m not even 100% sure these birds are necessarily males. Weird things happen with bird plumage sometimes. In this case, I’m thinking of female Mallards, which can develop male-ish coloration as they get older and their hormones get out of whack.

Any theories?

4 replies on “A Fancy Goldfinch”

Hello Rebecca, I liked your post on the raccoon. We once owned some American finches in the Avery Out in our garden here in the UK, we also noticed the changes in colour between the male and female, we put it down to the diet but as you mentioned we also found the changes became more prominent the older they got, sorry I can’t be more exact about why the changes happen. But keep up the post on your blog and have a very Merry Christmas.

Similar experience yesterday at feeders in Prospect Park, Brooklyn NY. This Goldfinch really stood out with its brightness, and the fact that it was alone among the House finches and Pine siskins. Usually always seem them in small flocks. No Redpolls in the park, but others keep seeing Crossbills.

As to the exact scientific reason for the variation in color, I haven’t a clue. I see it as no different than why some humans are blondes, some brunettes, some fair skinned, some dark skinned, it is due to our genetics as the species evolved. As to why the males of many species are brighter than the females, I have a theory about that and it has little to do with attracting a mate. Males sing to attract possible mates, but in watching a flock of birds fly off with the males brighly colored and the females rather dull, your eyes have a tendency to lock onto the brightly colored males. I’m sure it is the same as far as the eyes of a predator. The males of most species of anything are rather useless for anything other than mating, once mating is over, the males of many species don’t even assist in raising the young. But, what if their bright color makes them more vulnerable to predation? Their bright colors may insure survival of the species by the males becomming sacrificial offerings to predators, leaving the females and young to survive, and therefore the species survives. Could it be that females do select the brightest males to mate with, “knowing” that the males brigher colors make it more likely that he will be seen and therefore eaten, and that because of that, she and her brood is more likely to survive?

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