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The 'Common Poorwill', ''Phalaenoptilus nuttallii'', is a nocturnal
bird of the family Caprimulgidae, the
nightjars. It is found from
British Columbia and southeastern
Alberta, through the western
United States to northern
Mexico. The bird's habitat is dry, open areas with grasses or shrubs, and even stony desert slopes with very little vegetation.
Many northern birds
migrate to winter within the breeding range in central and western Mexico, though some remain further north. Remarkably, the Common Poorwill is the only bird known to go into
torpor for extended periods (weeks to months). This happens on the southern edge of its range in the United States, where it spends much of the winter inactive, concealed in piles of rocks. This behavior has been reported in
California and
New Mexico. Such an extended period of torpor is close to a state of
hibernation, not known among other
birds. It was described definitively by Dr.
Edmund Jaeger in 1948 based on a Poorwill he discovered hibernating in the
Chuckwalla Mountains of
California in 1946.
Jaeger's observations may have been influenced by earlier observations of torpor in the
White-throated Swift made by his acquaintance Wilson Hanna, a resident of the
Riverside, California area and noted
oologist.
In 1804,
Meriwether Lewis observed hibernating Common Poorwills in
North Dakota during the
Lewis and Clark Expedition. Though these observations were recorded carefully in Lewis's journal, their significance was not understood. This was at least in part because the Common Poorwill was not then recognized as a species distinct from the
Whip-poor-will of eastern
North America.
Native Americans of the
Hopi tribe were likely aware of the Poorwill's behavior even earlier—the Hopi word for the bird means "The Sleeping One".
This is the smallest North American
nightjar, about 18 cm (seven inches) in length, with a wingspan of approximately 30 cm (12 inches). It weighs 36-58 g. The sexes are similar, both gray and black patterned above. The outer tail-feathers are tipped with white, the markings slightly more prominent in the male.
The Common Poorwill is told from similar nightjars by its small size, short bill, rounded wings with tips that reach the end of the short tail at rest, and pale gray coloration. Like many other other
nightjars, the common name derives from its call, a monotonous ''poor-will'' given from dusk to dawn. At close range a third syllable of the call may be heard, resulting in a ''poor-will-low''. It also gives a ''chuck'' note in flight.
Up to five subspecies are described, although these are all quite similar, and some may be of dubious validity.
★ ''P. n. nutalli'' breeds over most of the North American range.
★ ''P. n. californicus'', Dusky Poorwill, is darker and browner than the nominate race. It occurs in western California.
★ ''P. n. hueyi'', Desert Poorwill, is paler than the nominate race. It occurs in southern California.
★ ''P. n. dickeyi'', San Ignacio Poorwill, is smaller and less heavily marked than ''californicus''. It is resident in
Baja California.
★ ''P. n. adustus'', Sonoran Poorwill, is paler and browner than the nominate race. It occurs from extreme southern
Arizona to central
Sonora.
Like other members of this family it feeds on nocturnal
insects such as
moths,
beetles, and
grasshoppers. It ejects pellets of the indigestible parts, in the manner of an
owl. The Common Poorwill frequently takes prey off of the ground or by leaping into the air from the ground. It is reported to drink on the wing.
The nest of the Common Poorwill is a shallow scrape on the ground, often at the base of a hill and frequently shaded partly by a bush or clump of grass. The clutch size is typically two, and the eggs are white to creamy, or pale pink, sometimes with darker mottling. Both sexes incubate for 20-21 days to hatching, with another 20-23 days to fledging. There is usually one brood per year, but females may sometimes lay and incubate a second clutch within 100 m of the first nest while the male feeds young at the first site. The young are
semiprecocial. An adult disturbed on the nest tumbles and opens its mouth, hissing, apparently imitating a
snake.
Breeding is from March to August in the south of the range, and late May to September further north.
The genus name ''Phalaenoptilus'' is a compound of Greek ''phalaina'', moth and ''ptilon'', feather. The species name ''nuttallii'' honors English-born American ornithologist
Thomas Nuttall.
References
★ Cleere and Nurney, ''Nightjars'', 1998, ISBN 1-873403-48-8
★ Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye, 1988. ''The Birder's Handbook''. New York: Simon and Schuster, ISBN 0-671-62133-5.
★ Terres, 1980. ''Audubon Society Encyclopedia of North American Birds''. New York: Alfred A. Knopf, ISBN 0-394-46651-9.
★ National Geographic Society, 1987. ''Field Guide to the Birds of North America''. Washington, D.C.: National Geographic Society. ISBN 0-7922-7451-2.
★ See also External links below.
External links
★
USGS
★
All About Birds--Cornell University
★
Arizona State University
★
Whatbird.com
★
Edmund Jaeger site
★
★
Jaeger's discovery--several articles discuss history of observations of hibernation in the Poorwill
★
San Bernadino County Museum--refers to Wilson Hanna, oologist
★
Common Poorwill photo gallery VIREO