Most birds with bright yellow or red feathers — think goldfinches and cardinals — use pigments called carotenoids to make those colors. "The reason that a bird's egg's yolk is a bright yellow ...

A 2003 study analyzed the feathers of an individual yellow Northern Cardinal. This specific bird lacked all of these reg pigments that were derived from what it had eaten. The authors believed ...

The yellow-rumped warbler is a migratory songbird ... delicately pointing at the bird’s soiled feathers with a gloved finger. More than a century later, fine particles of pollution still clung ...

Recent studies show that certain feather pigments can help neutralize toxic pollution. It means darker, duller birds could have a survival advantage. By Marta Zaraska Some popular city dwellers ...