Xanthochromistic purple finch
As a rule, IDing birds is easier than IDing arthropods (there are always exceptions, looking at you gulls!)
However, Nature likes to keep us on our collective toes, so she throws some “This is not at all how the field guide describes this bird” birds our way.
This week’s crawly is one of those. Meet the xanthochromistic purple finch, and his xanthochromistic kiddo. Make that “finches” and “kiddos.”
Let’s back up a bit. First we’ll say that it’s difficult enough to ID a purple finch when we also have house finches and Cassin’s finches in our area. In fact, “House Finch vs. Purple Finch” may just be its own Crawlies down the line.
One of the “easy” ways to tell a house finch from a purple finch is the color. Purple finches are raspberry colored, house finches are true red. So the field guides say:
Purple Finch, “In males, raspberry red coloration spreads relatively uniformly across upperparts, head, neck, and sides” Birds of the World
House Finch, “Adult males are rosy red around the face and upper breast” All About Birds
Now throw all of that out, because Nature has a sense of humor. Both house and purple finches can range in color. Purple can be golden yellow, coral, true red or raspberry. The vast majority of the time they are raspberry red. House can be golden yellow, orange or true red.
Both yellow and orange species of finch are xanthochromistic. Xanthochromistic is an unusually yellow pigmentation in an animal. Usually red pigmentation is replaced with yellow.
This color change from the norm can be caused by diet or genetics.
For house finches, their color is carotenoid color – so their diet is the key factor to their vibrance and place on the red to yellow color spectrum. We often see the example of white flamingoes. If flamingoes don’t get the brine shrimp rich in beta carotenes that give them their bright pink plumage, the birds become pale and whitish.
When it comes to purple finches, their red, orange or yellow coloration – while still xanthochromistic – is genetic.
Often off-color house finches are not as healthy as their true color flock mates, because the off-color males aren’t getting as rich a diet.
However, male purple finches of every hue are perfectly healthy (barring other non-diet related health issues).
Xanthochromism is far less common in purple finches than in house finches. Because it’s genetic in purple finches, one flock in one location will have a lot of off-color males while hundreds of other flocks will keep on being perfectly raspberry.
If you look at the Macaulay Library online here: https://www.macaulaylibrary.org/ you’ll see that there are pictures of off-color house finches from various observers in various places (and many of them). When you look at purple finches, you’ll see most of the off-color finch photos are from a handful of observers who have local off-color flocks.
Because xanthochromism is rarer in purple finches, it hasn’t been studied as well, only a couple of research resources are available. Many people assume the purples’ off-color is dietary like the house.
Because I’m lucky enough to have one of those off-color flocks in my yard (also had several sightings in my yard in Trail – gotta love our area!) I’ve been able to document coral-colored male purple finch having coral-colored male kiddos two years running.
Someday maybe I’ll be able to document a yellow or pale pink male with their yellow or pale kids, but for now Mr. and Mrs. Coral have exclusive property rights to the prime nesting spot closest to the feeders.
