| Common poorwill | |
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Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Clade: | Strisores |
| Order: | Caprimulgiformes |
| Family: | Caprimulgidae |
| Genus: | Phalaenoptilus Ridgway, 1880 |
| Species: | P. nuttallii |
| Binomial name | |
| Phalaenoptilus nuttallii (Audubon, 1844) | |
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Breeding Year-round | |
| Synonyms | |
Caprimulgus nuttallii (protonym) | |
Thecommon poorwill (Phalaenoptilus nuttallii) is anocturnalbird of the family Caprimulgidae, thenightjars. 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 birdsmigrate to winter within the breeding range in central and western Mexico, though some remain further north. The common poorwill is the only bird known to go intotorpor for extended periods (weeks to months).[2] 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. Such an extended period of torpor is close to a state ofhibernation and is not known among other birds.
The common poorwill was illustrated andformally described in 1844 by the ornithologistJohn James Audubon from a male specimen collected on the eastern bank of theMissouri River betweenFort Pierre and mouth of theCheyenne River inSouth Dakota. Audubon coined thebinomial nameCaprimulgus nuttallii, choosing the specific epithet to honour his friend, the ornithologistThomas Nuttall.[3][4] The species was moved to its owngenusPhalaenoptilus by the American ornithologistRobert Ridgway in 1880.[5] The genus name combines theAncient Greekphalaina meaning "moth" andptilon meaning "plumage".[6]
Sixsubspecies are recognised:[7][8]
This is the smallest North Americannightjar, about 18 centimetres (7.1 in) in length, with a wingspan of approximately 30 centimetres (12 in). It weighs 36–58 grams (1.3–2.0 oz). 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.[9]
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.[9] Like many othernightjars, the common name derives from its call, a monotonouspoor-will given from dusk to dawn. At close range a third syllable of the call may be heard, resulting in apoor-will-low. It also gives achuck note in flight.[9]
The common poorwill is the only bird known to go intotorpor for extended periods (weeks to months).[2] 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 ofhibernation, not known among other birds. It was described definitively by Dr.Edmund Jaeger in 1948 based on a poorwill he discovered hibernating in theChuckwalla Mountains of California in1946.[10]
In 1804,Meriwether Lewis observed hibernating common poorwills in North Dakota during theLewis 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 thewhip-poor-will of eastern North America. Native Americans of theHopi tribe were likely aware of the poorwill's behavior even earlier — theHopílavayi name of this bird,hölchko, means "The Sleeping One".[11][12][13]
Breeding is from March to August in the south of the range, and late May to September further north. 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.[11] 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.
Like other members of this family it feeds on nocturnalinsects such asmoths,beetles, andgrasshoppers.[11] It ejects pellets of the indigestible parts, in the manner of anowl. 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.
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