So, it makes a lot of sense for birds to change color in response. In the study, researchers drew information from over 1200 bird species, showing how urbanization changes feather colors.

Now, research has revealed these stunning birds are also sending secret color signals that are invisible to human eyes.

Gavriel Jecan / Corbis For decades, scientists have known how birds with yellow or red feathers usually get their color: It comes from pigments in foods the birds eat. Flamingoes, for instance ...

Among the peacock, the toucan, and the macaw, there’s a kaleidoscope of color in the avian family. And then there are the blue birds, the ones that are supposed to bestow happiness wherever they go.

For bill color, see sidebar below ... Juvenile: Brown and buff head; streaked underparts. The white-throated sparrow has a dark bill, prominent white throat, and yellow supraloral.

Had evolution finessed the spiders’ color scheme to warn off birds without also alerting beetles? The first part of his experiment, started at Duke University, required plastic widows made with ...