Numbers in the News: Bird Migration

Each fall, more than 4.7 billion birds in the U.S. fly south for the winter. Here are some facts and figures about how people are making this annual migration safer for them.

The number of birds killed by collisions with buildings in the U.S. each year. Many buildings are lit up all night, which disorients migrating birds.

The reduction in bird collisions that can occur on a single building after darkening half the windows.

The hours during which businesses in New York City must turn off nonessential lights during migration season.

The number of U.S. states that have laws in place to reduce light pollution.

^{SOURCES: NATIONAL AUDUBON SOCIETY, INTERNATIONAL DARK-SKY ASSOCIATION, CORNELL LAB OF ORNITHOLOGY, NATIONAL CONFERENCE OF STATE LEGISLATURES, U.S. DEPARTMENT OF AGRICULTURE}