Common Poorwill (Phalaenoptilus nuttallii)

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Image of a Common Poorwill in its natural habitat
Birds Poorwill

Introduction

The Common Poorwill (Phalaenoptilus nuttallii) is a small nocturnal nightjar of western North America. It is recognised for its cryptic plumage, distinctive repeated call and unusual ability to enter prolonged torpor during periods of cold or limited food. During daylight, it usually rests motionless on the ground or among rocks, where it is difficult to detect.

Physical Description

The Common Poorwill is approximately 19–21 cm long and weighs about 31–58 g. It has a compact body, a broad, flattened head, short rounded wings and a relatively short tail. Its bill appears small but opens very widely, allowing it to catch and swallow sizeable flying insects.

The plumage is a mottled mixture of grey, brown, buff and whitish markings, producing a dead-leaf pattern that blends with bare soil, stones, leaf litter and dry vegetation. A narrow white throat band is present but can be difficult to see on a resting bird. In flight, adult males usually show more obvious white tips on the outer tail feathers, while those of females are generally buffier and less conspicuous. Juveniles are similarly cryptic but may appear softer and less sharply marked than adults.

Range and Habitat

The species occurs from southern British Columbia and southern Alberta through the western United States and south into northern Mexico. It uses open, dry or semi-arid habitats, including rocky foothills, plateaus, washes, sagebrush flats, chaparral, pinyon–juniper woodland, scrub and some desert environments. In the eastern part of its range it may also occur in open habitats with scattered spruce and aspen.

Common Poorwills generally avoid dense forest and grassland with heavy ground cover. They often roost on bare ground, among rocks or beneath shrubs, and are commonly found at low to middle elevations. In the western United States, suitable habitat is often between roughly 300 and 2,100 metres, although the elevation range varies geographically.

Northern populations are commonly migratory, whereas some populations in the southern part of the range are resident or move shorter distances. Regional plumage variation occurs across the species’ broad distribution, but the species remains taxonomically recognised as Phalaenoptilus nuttallii.

Behaviour and Diet

Common Poorwills are primarily active from dusk through the night and may also forage shortly before dawn. Males give a repeated, whistled call resembling “poor-will” or “poor-willip”, especially during the breeding season and on warm nights.

They usually hunt from a low perch on the ground, a rock or a low branch. From there, they make short aerial sallies to catch flying insects, often returning to the same perch. Moths and beetles form much of the diet, supplemented by grasshoppers, flying ants, flies and other insects. Undigested material is later expelled as pellets.

The species is one of the best-known examples of avian torpor. During cold conditions or periods of energetic stress, a Common Poorwill can substantially reduce its body temperature and metabolic rate. Extended torpor has been documented outside the breeding season, although active nesting and parental care limit its use during reproduction. Torpor is more accurately described as prolonged torpor or hibernation-like dormancy than as mammalian hibernation.

Breeding takes place during the warmer months. The female lays two eggs directly on stony or sandy ground, sometimes on leaf litter or pine needles near a shrub, cactus or rocky outcrop. No conventional nest is built, although there may be a slight scrape. Incubation lasts about 20–21 days, and young birds remain dependent at the nest site for approximately 20–23 days after hatching. Both adults share incubation and care of the young.

Identification Tips

  • Look for a small, compact nightjar with a broad head, short tail and rounded wings.
  • The grey-brown and buff “dead-leaf” pattern is the most important daytime feature. A motionless bird on bare ground or among rocks may be almost invisible.
  • A narrow white throat band can help confirm the identification, although it may be hidden when the bird is resting.
  • At night, listen for the repeated, whistled “poor-will” or “poor-willip” call.
  • In flight, the bird usually stays relatively low and flies with an erratic, moth-like pattern. A Common Nighthawk is larger, longer-winged and more noticeably buoyant in flight.
  • Males in flight may show clear white tail tips. Female tail markings are usually duller and more buff-coloured.

Conservation Status

The Common Poorwill is currently assessed as Least Concern on the IUCN Red List. It is not considered globally threatened, but local populations may be affected by the loss and fragmentation of open dry habitats, urban expansion, agricultural conversion and vehicle strikes. Partners in Flight and Cornell’s bird guide have also reported a long-term population decline in North America.

Conservation measures include retaining native scrub, rocky open country and other suitable breeding habitat, protecting connected dryland landscapes, and reducing disturbance and vehicle mortality where birds regularly forage or roost. More regional monitoring is useful because population trends and threats are not uniform across the species’ range.

Frequently Asked Questions

Where can the Common Poorwill be found?

It occurs across western North America, from southern British Columbia and southern Alberta through the western United States and into northern Mexico. It is most often associated with open, dry and rocky habitats.

Is the Common Poorwill nocturnal?

Yes. It is mainly active at night, with particularly noticeable calling and foraging around dusk and before dawn. During the day it generally rests on the ground or among rocks.

What does the Common Poorwill eat?

It feeds mainly on flying insects, especially moths and beetles. Grasshoppers, flying ants, flies and other insects are also eaten.

Can the Common Poorwill hibernate?

It can enter prolonged torpor, during which body temperature and metabolic rate fall substantially. This hibernation-like state is best documented during cold or energetically stressful periods, particularly outside active breeding.

Where does the Common Poorwill nest?

It lays its eggs directly on bare, stony or sandy ground, sometimes on leaf litter or pine needles. The site is often beside a shrub, cactus or rocky outcrop, and the species does not construct a conventional nest.

How can the Common Poorwill be identified at night?

The most reliable clue is its repeated whistled call, which resembles “poor-will” or “poor-willip”. A small nightjar flying low over open, dry ground and returning to a low perch may also be a Common Poorwill.

References

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