What is the only bird that hibernates?

The only bird known to hibernate is the common poorwill.

Strictly speaking, scientists often describe the behavior as prolonged torpor rather than true mammalian-style hibernation. The common poorwill can lower its body activity for weeks or months during cold periods, remaining concealed and inactive rather than migrating or continuously feeding. That unusually long torpor is why it is widely recognized as the only known hibernating bird.

The species lives across western North America, from British Columbia and Alberta through the western United States to northern Mexico. Some individuals migrate, but birds near the southern edge of the United States range may shelter in rocky crevices or piles of stones through winter. Their camouflage makes these inactive birds difficult to find.

Naturalist Edmund Jaeger documented the behavior in detail after finding a poorwill in California’s Chuckwalla Mountains in 1946. Meriwether Lewis had recorded similar observations during the Lewis and Clark Expedition in 1804, but their significance was not understood at the time. The common poorwill is often confused with the eastern whip-poor-will, a different nightjar that does not have the same established hibernation record.