Basically, if you look at the bird from one side, it's completely red, but from the other its feathers are white.
That's significant because it is the male cardinals that are well-known to be dark red - consider if you will, the mobile phone game Angry Birds - whereas the females are typically white.
This particular bird, which was captured and tagged up by the USA's Inland Bird Banding Association, has a rare genetic anomaly called bilateral gynandromorphism.
That means that, as well as the funky feathers, it shares both male and female genitalia and has both an ovary and a testis.
The bird is a regular visitor to the place where it was caught, having first been banded back in 2014. However, it returns to the feeders each year, who are lucky enough to marvel at this incredible irregularity of nature.
Since the wildlife organisation shared the picture on their Facebook page, it has become something of a viral celebrity.
More than 6,800 people have commented on the bird's unique appearance, and the original post - from late November - has been shared more than 58,000 times.
That's more than most of us achieve in our lifetime, and this is just a bird.
Among the comments are a load of people marvelling at the spectacular variety of nature.
One person said: "Rare abnormality aside, this is a breathtakingly beautiful bird!
"Interesting, nature is always experimenting, we just don't always get to see the results. He/she does not appear to be too pleased with the current situation. That's one grumpy face."
Another offered: "Isn't nature amazing? So much variety and science to think about!"
Yup, that's certainly true.
Also, at least from one side, it definitely looks like an Angry Bird.
While this is a rare phenomenon, particularly in birds, it is actually a bit more common than you might think in insects.
For example, one out of every 10,000 butterflies possesses the anomaly.
OK, so that's still pretty rare, but you get the idea.
Since it was first observed in the 1800s, scientists have found crabs, snakes, bees, and other types of bird that are bilaterally gynandromorphic.
Oh, and check out the lobster that exhibits the rare trait, too. It's seriously weird, but also really cool.
Featured Image Credit: Inland Bird Banding Association
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