Phalaenoptilus nuttallii

Common poorwills range throughout western North America from south central British Columbia and southwestern Saskatchewan to central Mexico. Northern populations migrate to the southern portions of their range, from California, Arizona, and Texas to central Mexico, from September to November and return April to May. This migration may vary by a month depending upon weather conditions and the portion of the breeding range occupied. Southern populations arrive for breeding season from February to March and leave October to November for their winter range. Some southern populations occupy the same region year round but migrate to higher elevations for the breeding season and to lower elevations during the winter.

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: BREEDS: southern British Columbia, southeastern Montana, northwestern South Dakota, Nebraska, and southwestern Iowa south on west coast from central California to southern Baja California, and through eastern Kansas and central Texas to central mainland of Mexico. WINTERS: from central California, southern Arizona, and southern Texas south to limits of breeding range in Mexico.

Common poorwills are medium-sized birds with an adult length of 19 to 21 cm. The average mass within a sample of Phalaenoptilus nuttallii in British Columbia was 47.2 +/- 6.0 grams for males and 49.5 +/- 6.3 grams for females. Average wing span in that sample was 42.7 cm for males and 44.1 cm for females. Weight ranges vary among populations and with the time of year. Males lose weight early in the breeding season and both sexes gain weight prior to migration. The size of males and females is similar with females tending towards slightly larger average measurements than males.

Overall color ranges from mottled brown and white to mottled black and white patterns. The ventral side is grey-white with thin charcoal lateral bands progressing to a dark band at the throat. The dorsal surface has cryptic mottled pattern in grey, black, and brown shades and the lateral tail feathers have black and brown bands with white or dun colored tips. The wings are sandy and brown barred at the dorsolateral trailing side and mottled on the medial leading edge. The beak has a ventral curve, is short and wide, and has large open gape with pronounced bristles extending laterally from base.

The species can be distinguished from other members of the Caprimulgidae family in North America by a thicker white throat patch and short tail length. The wingtips extend to the end of the tail when folded, and a large head appears to transition to body without a neck, giving them a stout appearance. The other members of this family have a longer tail extending past the wingtip and do not have the typical lateral white or buff coloured rectrices found in common poorwills. Males and females are relatively monomorphic with only small distinguishing characteristics such as white tipped rectrix feathers for males and buff for the females. Juveniles have similar appearance to adults as well.

Common poorwills are polytypic, with five described subspecies based in large part upon geography even though the winter ranges appear to overlap. However, the existence of subspecies is debatable without additional genetic research. In addition, light and dark morphs exist throughout the range making differentiation, based upon appearance, between subspecies and morphs difficult.

Range mass: 42.8 to 58.1 g.

Average mass: 51.6 g.

Range length: 19 to 21 cm.

Average wingspan: 42.7 to 44.1 cm.

Average basal metabolic rate: 0.8 cm^3 oxygen/hour.

Other Physical Features: endothermic ; heterothermic ; bilateral symmetry ; polymorphic

Sexual Dimorphism: sexes alike; female larger; sexes colored or patterned differently

Length: 20 cm

Weight: 52 grams

Systems

• Terrestrial

Common poorwills are found in dry, open areas in diverse habitats such as grasslands, forest, hills, and deserts. Vegetation varies, with preference given to short grasses and shrubs or open forest in areas with deciduous or coniferous growth. Trees or shrubs reported in proximity to nesting and roosting areas include, but are not limited to, such species as white fir, ponderosa pine, trembling aspen, Jeffrey pine and creosote. Roost sites are chosen for proximity to bare ground, vegetative debris, and are usually open with little live vegetation cover. Common poorwills typically nest at elevations between 500 to 1000 meters, with some found over 2500 meters.

Range elevation: 500 to 2500 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: savanna or grassland ; chaparral ; forest ; scrub forest ; mountains

Comments: Scrubby and bushy areas, prairie, desert, rocky canyons, open woodland and broken forest, primarily in arid or semiarid habitats (AOU 1983). Found in valleys and foothills, mixed chaparral-grassland, and pinyon-juniper habitat. Nests in open areas on a bare site.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Breeding populations in most of U.S. move south for winter. Found year-round in southern half of range.

Common poorwills are insectivorous, with a diet consisting largely of night flying beetles (Coleoptera) and moths (Lepidoptera). Other insect orders do not exceed 10 % of the diet, as determined by analysis of fecal pellets. Prey appear to be selected for size with minimum lengths of 5 to 7 mm. This selectivity may maximize the energy obtained from food sources or it may represent the lower limit of the insects that can be visually detected in low light conditions. One study estimated that common poorwills make 200 to 300 flights per night to obtain a minimum of 9.7 g of insects to maintain weight during the breeding season. Hunting is in low light conditions from dusk to dawn. There appears to be a minimum amount of light required, as hunting activity increases during moonlight nights compared to dark nights. Common poorwills use an ambush hunting style, as they prefer to wait on the ground or low perch and fly almost vertically upwards to a maximum of 3 meters once a desired insect has been spotted. Long flights for foraging are rare and most last about three seconds before they return to the ground. Large eyes adapted for low light conditions and a large gaping mouth for prey capture are adaptations that enhance this hunting style.

Animal Foods: insects

Primary Diet: carnivore (Insectivore )

Comments: Insectivorous. Feeds on or close to the ground at night. Feeds on night-flying moths, beetles, grasshoppers, locusts, etc. Catches insects on the ground or vaults upward and captures insects in the air. Sit-and-wait predator.

It is not known whether common poorwills have mutualistic relationships with other species. However, they serve as hosts for at least two species of parasites. Lice (Ethiopterum macrocephalum) has been found infesting the crown and nape of a common poorwill and mites (Ptilonyssus niitzchi) have been found in the nasal passages. Common poorwills have further roles as both predators of nocturnal insects and as prey for carnivorous mammals, snakes, owls, and hawks.

Commensal/Parasitic Species:

• lice (Ethiopterum macrocephalum)
• mites (Ptilonyssus niitzchi)

Common poorwills have several behavioral adaptations to minimize predation. These include nocturnal activity to avoid most daytime predators and sitting still when roosting or when on the nest, to prevent movement from being detected. Incubating parents may attempt to lead intruders away from the nest by feigning injury and landing close by to the nest once flushed. Moving the eggs and nestlings also helps prevent detection by predators since the buildup of fecal matter reveals their presence to some predators. In addition, their cryptic coloration makes them difficult to detect. Common poorwill may limit their calling when they hear calls by predatory nocturnal animals like owls. Nonetheless, losses due to predation can be high and numerous species are recorded or are strongly suspected to be predators of P. nuttallii. These include, but are not limited to, northern harriers, great horned owls, western screech-owls coyotes, badgers, foxes, skunks, rattlesnakes, and gopher snakes.

Known Predators:

• great horned owls (Bubo virginianus)
• western screech-owls (Otus kennicottii)
• coyotes (Canis latrans)
• American badgers (Taxidea taxus)
• northern harriers (Circus cyaneus)
• rattlesnakes (Crotalus)
• gopher snakes (Pituophis melanoleucus)
• foxes (Vulpes)
• striped skunks (Mephitis mephitis)

Anti-predator Adaptations: cryptic

Males set up territories up to 500 meters across early in the breeding season (Kalcounis et al. 1992).

Common poorwills appear to primarily communicate using songs or calls. The same vocalization for mating is also used for communication. Both sexes make the same call, poor-will-ow in the 1.5 kHz range. The call is made year round, although frequency and duration of calling increases among males during mating season. The song is used by males to advertise their presence in a territory and to attract females. Recorded common poorwill calls played in a territory will attract the male. Wing clapping has been reported in one instance (Mengel, Sharpe and Woolfenden, 1972), but whether it is used for courtship or territorial defense has not yet been established.

Common poorwills have large eyes suited for seeing in low light conditions and from positions on ground or on low perches. Vision and hearing are thus the two primary senses used by this species to assess surroundings.

Communication Channels: visual ; acoustic

Comments: Has been observed in winter hibernation in California and New Mexico (Ryser 1985; Terres 1980). More active on nights with bright moonlight versus nights with none (Auk 109:315-320).

Common poorwill lifespan in captivity is not available in the literature, as the species does not adapt well to human care. There is limited information on longevity in the wild. Several banded individuals were captured over two consecutive seasons (Csada and Brigham, 1994). As well,the same individual returned to a hibernation site over 3 winters before disappearing (Jaeger, 1949). The longest lifespan, recorded in literature, for an individual in the wild is therefore at least three years.

Range lifespan
Status: wild: 3 (high) years.

Observations: In the wild, these animals have been reported to live more than 3 years (http://www.demogr.mpg.de/longevityrecords). Their maximum longevity is likely underestimated, though. Annual mortality is about 47% (http://bna.birds.cornell.edu/).

Male common poorwills establish a territory upon return to their breeding area in the spring and actively defend the territory against other males. Energy expenditure for males for calling and territory defense has been measured to be 5.1 time the usual basal metabolic rate. This means that males have one of the highest energy expenditure rates relative to basal metabolic rates when breeding as compared to other birds (>95% of other species). Females do not have similarly high levels and the field metabolic rate for males decreases over summer to near that of females by the time of the second brood.

There is no distinguishing characteristic between mating calls and songs in male common poorwills and similar vocalizations have also been reported for females. The song consists of a three note poor-will-ow sound in the 1.5 khz range. The calling frequency for males is much higher during the start of breeding season and occurs from evening through the night to dawn while on low perches or the ground.

It is not known if the arrival of males coincides with the arrival of females for the start of breeding season. There has been suggestion that males and females return to the same areas over consecutive seasons in northernmost populations, but further research is required. Also, pairs are monogamous over a single breeding season. Very little is known about common poorwill mate selection and reproductive behavior due primarily to their nocturnal activity.

Mating System: monogamous

Common poorwill pairs typically lay the first eggs soon after arrival in their breeding range in late May to June in Canadian populations. A second clutch is laid July to August in a nest approximately 100 meters from the first and the male has been reported to continue feeding the young from the first clutch even as the female incubates the second. Incubation duties are shared between males and females. There are typically two buff colored eggs per clutch laid over two consecutive days and each clutch is incubated for 20 to 21 days. Mass at hatching is reported to be about 4 grams. Nestlings are cared for a period of 20 to 22 days after hatching until they have fledged and first flight, indicating independence, is at 20 to 23 days. Nesting sites are usually on the ground in small open areas that have some shelter provided by nearby low objects such as rocks, shrubs or fallen trees. No nests are built, other than small shallow depressions on the ground. Eggs and nestlings are moved short distances of 1 to 3 meters every couple of days for thermoregulation or in response to disturbance by intruders. The age of sexual maturity for common poorwills is not known.

A remarkable aspect of incubation and brooding is the ability of the parent to enter into torpor in response to inclement weather. Parents in torpor with cloacal temperatures as low as 11.5 degrees Celsius have been discovered incubating eggs. However, even though this adaptation saves parental energy, it has the consequence of reducing egg viability and results in higher rates of nest abandonment.

Breeding interval: Common poorwills breed twice per year.

Breeding season: Common poorwill breeding sually occurs May to September.

Average eggs per season: 4.

Range time to hatching: 20 to 21 days.

Average birth mass: 4 g.

Range fledging age: 20 to 22 days.

Range time to independence: 20 to 23 days.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Both common poorwill parents share incubation duties until hatching. The timing of and amount of care each parent provides for eggs or nestlings differs between pairs. The male is more likely to incubate eggs during the day. After hatching, females are more likely to brood nestlings during daytime. The parent brooding or incubating during the day is not relieved until evening and then eggs or nestlings may be left for short periods during nocturnal hours while the parents hunt. The behavior of limiting daylight movement and relying on camouflage presumably helps protects against predators active during daylight.  Parents remain still during nesting until a person or predator approaches within a distance of 1 meter. At that point, the parent will usually flush from the nest. They may also make hissing or growling noises, fluff their feathers, or elevate their wings in attempt to intimidate intruders, while staying put on the nest. Parents may attempt to distract predators from the nesting site by landing close by after flushing and calling. The nestlings are fed a diet of regurgitated insects until they have fledged. Association of the first clutch with the parents until the hatching of the second clutch has been reported, but may not be typical for the species.

Parental Investment: altricial ; male parental care ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); post-independence association with parents

Breeding begins in late March in south to late May in north. Both sexes alternate incubating 2 eggs. The nestlings are semi-precocial and downy.

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 6 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 6
Specimens with Barcodes: 7
Species With Barcodes: 1

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2008
  Least Concern
• 2004
  Least Concern

Common poorwills are listed as an IUCN species of least concern and are not listed in the CITES appendices. Although populations are presumed to migrate from Canada and the United States to Mexico, they are not be protected under the United States Migratory Bird Treaty Act. Populations are presumed to be large, although the distribution may be somewhat fragmented. They may benefit from human activities such as cattle grazing or logging, as they create open habitats.

US Migratory Bird Act: no special status

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N4B - Apparently Secure

United States

Rounded National Status Rank: N5B,NNRN : N5B: Secure - Breeding, NNRN: Unranked - Nonbreeding

Rounded Global Status Rank: G5 - Secure

There are no reported adverse effects of Phalaenoptilus nuttalli on humans.

Common poorwills prey on nocturnal insects such as moths and beetles. No research has been done regarding the specific insect species that they prey on, but presumably some are pests of agriculture and forestry.

Of great interest to scientists is the ability of common poorwills to go into torpor in response to environmental stress, such as decreased food sources or inclement weather. Numerous studies have been done investigating this phenomenon. The lack of mitochondrial uncoupling proteins in their adipose tissues, suggests convergent evolution to a similar characteristic found in hibernating bats.

Positive Impacts: research and education; controls pest population