In 1946, the scientific community was shocked by the discovery of a Common Poorwill that was cold to the touch and appeared not to be breathing or to have a heartbeat. Although poorwills do not enter true hibernation like some mammals, they use short-term 'torpor'-their body temperature drops as low as 43° F (6° C) for a few days at a time-to survive cold periods when their prey (flying insects) are unavailable. Not all poorwills use torpor; many of them migrate to tropical climates for winter. The 1946 discovery was clearly not the first suggestion of this strange habit in poorwills. In 1804, Meriwether Lewis found a mysterious 'goatsucker ... to be passing into the dormant state.' Perhaps the scientific community's amazement was needless: the Hopi could have told them their name for the bird was Hölchoko, 'the sleeping one.'
I.D.: Sexes similar: cryptic, light to dark brown plumage; pale throat; finely barred underparts. Male: white corners on the tail feathers. Female: buff corners on the tail feathers.
In flight: rounded wings and tail.
Size: L 71/2-81/2 in. (19-22 cm).
Range: locally common in drier mountain habitats in Montana, Idaho and western Colorado.
Habitat: dry, open, grassy environments, rocky canyons, ponderosa pine forests and open shrublands in the foothills.
Nesting: typically on the Great Plains and in the Southwest; on bare ground; pair incubates 2 white eggs for 20-21 days.
Feeding: on the wing; eats mainly moths, beetles and other flying insects.
Voice: frequently heard at dusk and through the night: poor-will poor-will; at close range, a hiccup-like sound can be heard at the end of the phrase.
Similar Species: Common Nighthawk: long, pointed wings; white wrist patches.