This is Bird Note.

Northern Cardinals are known for their iconic red feathers. Males are bright scarlet,

and females sport red wing and crest feathers. So if you saw a Northern Cardinal

that was lemon yellow, you might think it was a different species entirely.

In fact, these are northern cardinals, but with a genetic mutation.

All cardinals ingest yellow pigments in their food.

Most cardinals' bodies change them into red pigments, giving their feathers their signature shade.

But just a few cardinals lack this ability, resulting in a bright yellow bird.

Unexpectedly yellow birds occur in other species too, from house finches that look like they've been dipped in egg yolk, to red-bellied

woodpeckers with golden-hued head feathers.

The condition is called xanthochromism.

Xanthochromism and other color abnormalities are rare, just a handful in every few million bird sightings.

And the causes for these conditions vary.

For house finches, diet alone is probably enough to turn them yellow.

Field guides show only a few illustrations for a single species,

but part of the fun is finding all the shades of variation in well-known birds.

For Bird Note, I'm Ariana Rimmel.