A bay-breasted warbler weighs about the same as four pennies, but twice a year makes an extraordinary journey. The tiny songbird flies nearly 4,000 miles (6,437 kilometers) between Canada's spruce forests and its wintering grounds in northern South America.
“Migratory birds are these little globetrotters,” said Jill Deppe, the senior director of the migratory bird initiative at the National Audubon Society.
