Many warblers have olive-green backs, yellow breasts and black feather accents.  Think of hooded, prairie, Wilson’s and Kentucky warblers like this one.  Why are so many of them this color?

Steve Gosser’s photo shows why.

By the time a warbler nests in North America, the leaves are out and the forest’s light is soft yellow-green.  Seen by a predator from above, the warblers’ olive color matches the dark understory.  From below their yellow breasts match the light filtering through the leaves.  Their black accent feathers break up the colors and look like shadows.

In the winter the warblers live in leafy places in Central and South America where they continue to match the habitat.

Yellow is camouflage.

(photo by Steve Gosser)