Which extinct North American bird once formed flocks of billions before its 1914 extinction?

The extinct North American bird that once formed flocks of billions was the passenger pigeon.

The passenger pigeon was once North America’s most abundant bird, ranging across the eastern United States and Canada. Its enormous, constantly moving flocks searched for mast, fruit, and other food, and historical estimates place the total population at roughly 3 billion birds, with some estimates reaching 5 billion. A single flock could darken the sky and occupy vast stretches of forest.

That abundance did not protect the species. Commercial hunting supplied cheap meat, while large-scale logging and farming destroyed its breeding and feeding habitat. The pigeon’s extreme social behavior also made it vulnerable: it depended on huge communal colonies, so fragmented populations struggled to reproduce successfully.

The last confirmed wild bird was reportedly shot in 1902. Martha, the last known passenger pigeon, died at Cincinnati Zoo on September 1, 1914. The bird is sometimes confused with the mourning dove, but genetic evidence places it closer to Patagioenas pigeons. Its extinction became a powerful lesson in conservation and wildlife management.