Common Nighthawk
Encyclopedia
The Common Nighthawk is a medium-sized crepuscular
or nocturnal bird, whose presence and identity are best revealed by its vocalization. Typically dark (grey, black and brown), displaying cryptic colouration and intricate patterns, this bird becomes invisible by day. Once aerial, with its buoyant but erratic flight, this bird is most conspicuous. The most remarkable feature of this aerial insectivore is its small beak belies the massiveness of its mouth. Some claim appearance similarities to owls
. With its horizontal stance and short legs, the Common Nighthawk does not travel frequently on the ground, instead preferring to perch horizontally, parallel to branches, on posts, on the ground or on a roof. The males of this species may roost together but the bird is primarily solitary. The Common Nighthawk shows variability in territory size.
This caprimulguid has a large, flattened head with large eyes; facially it lacks rictal bristles. The Common Nighthawk has long slender wings that at rest extend beyond a notched tail. There is noticeable barring on the sides and abdomen, also white wing-patches.
The Common Nighthawk measures 22-25 cm in length, displays a wing span of 21-24” / 54–61 cm, weighs 62-98 g, and has a life span of 4–5 years.
The American Orinthologists’ Union treated the smaller Antillean Nighthawk
as conspecific with the Common Nighthawk until 1982.
Up until the early 19th century, the Common Nighthawk and the Whip-poor-will
were thought to be one species. The latter’s call was explained as the nocturnal expression of the Common Nighthawk. Alexander Wilson
, “The Father of American Ornithology” correctly made the differentiation between the two species.
Chordeiles minor neotropicalis (Selander & Alvarez del Toro, 1955)
Chordeiles minor howelli (Oberholser, 1914)
Chordeiles minor hesperis (Grinnell, 1905)
Chordeiles minor aserriensis (Cherrie, 1896)
Chordeiles minor chapmani (Coues, 1888)
Chordeiles minor sennetti (Coues, 1888)
Chordeiles minor henryi (Cassin, 1855)
Chordeiles minor minor (J. R. Forster, 1771)
, from Virginia to California and from Wyoming to Texas.
In the late 19th and early 20th century, because they held the title of "hawk
" in their names, had habits of diurnal insect hunting, and the fact that they travelled in migrating flocks, worked against these birds in that they were hunted for sport, nourishment and as predators.
The Common Nighthawk resembles both the Antillean Nighthawk
and Lesser Nighthawk
. The Lesser Nighthawk is a smaller bird and displays more buffy on the undertail coverts, where the Common Nighthawk shows white. Common Nighthawks and Antillean Nighthawks exhibit entirely dark on the basal portion of the primary feathers, whereas Lesser Nighthawks have bands of buffy spots. Common Nighthawks and Antillean Nighthawks have a longer, outermost primary conveying a pointier wing tip than the Lesser Nighthawk. The Common Nighthawk forages higher above ground than the Lesser Nighthawk and has a different call. The Antillean Nighthawk may only be distinguished as different from the Common Nighthawk, once in the hand. Subtle differences are recorded to be a challenge in field identification.
al growth occurs over the succeeding years or decades. The Common Nighthawk is drawn into urban built-up areas by insects.
The Common Nighthawk is the only Nighthawk occurring over the majority of northern North America.
Food availability is likely a key factor in determining which and when areas are suitable for habitation. The Common Nighthawk is not well designed to survive in poor conditions, specifically low food availability. Therefore, a constant food supply consistent with warmer temperatures is a driving force for migration and ultimately survival.
It is thought that the bird is not able to enter torpor
, although recent evidence suggests the opposite.
The Common Nighthawk will migrate by day or night in loose flocks; frequently numbering in the thousands, no visible leader has been observed. The enormous distance travelled between breeding grounds and wintering range displays one of the North America’s longer migrations. The north bound
journey commences at the end of February and the birds reach destinations as late as mid June. The south bound migration commences mid July and reaches a close in early October.
While migrating, these birds have been reported travelling through middle America, Florida, the West Indies, Cuba, the Caribbean and Bermuda, finally completing their journey in the wintering grounds of South America, primarily Argentina.
As aerial insectivore
s, the migrants will feed on route, congregating to hunt in marshes, rivers and on lakeshores. In Manitoba and Ontario, Canada, it is reported that during migration the Nighthawks are seen most commonly in the late afternoon, into the evening, with a burst of sunset feeding activities.
Additionally, it has been noted that during migration the birds may fly closer to the ground than normal; possibly foraging for insects. There is speculation that feeding also occurs at higher altitudes.
The Common Nighthawk winters in the South Americas, but distribution in this locale is poorly known due to difficulties in distinguishing the bird from the Lesser Nighthawk
and in differentiating between migrants and over wintering birds. In some South and Central American countries, a lack of study has led to restricted and incomplete records of the bird. Records do support wintering in Ecuador, Peru, Bolivia, Brazil, Paraguay, Uruguay and Argentina.
and rectrices are replaced in the post-juvenile moult
. Post-juvenile moult commences in September at the breeding grounds; majority of the body plumage is replaced but wing-coverts and rectrices are not completed until January–February, once the bird arrives at the wintering grounds. There is no other moult prior to the annual moult of the adult. The Common Nighthawk adults have a complete moult that occurs mostly or completely on wintering grounds and is not ceased until January or February.
Croaking auk auk auk vocalized by males while in the presence of a female during courtship. Another courtship sound, thought to be made solely by the males, is the boom, created by air rushing through the primaries after a quick down flex of the wings during a daytime dive.
Hissing cluck heard by females, and wing-clapping by male during nest defence. Strongly territorial males perform dives against fledglings, females and intruders such as humans or raccoons.
Vision presumed to be main detection sense. No evidence exists to support the use of echolocation. The birds have been observed to converge on artificial light sources in an effort to forage for insects enticed by the light. The average flight speed of Common Nighthawks is 23.4 kilometers per hour.
No evidence suggests this bird casts pellets.
The Common Nighthawk is recognized to discharge feces around nest and roosting positions. The bird will sporadically defecate in flight. Defecation is pungent.
, however sometimes a second later brood. The bird is assumed to breed every year. Reuse of nest
s by females in subsequent years has been reported. A monogamous pattern has also recently been confirmed.
Courting and mate selection occurs partially in flight, the male dives and booms (see Vocalization) in an effort to garner female attention, the female may be in flight herself or stationary on the ground.
Copulation occurs when the pair settles on the ground together; the male with his rocking body, widespread tail wagging and bulging throat expresses guttural croaking sounds. This display by the male is performed repeatedly until copulation.
The preferred breeding / nesting habitat is in forested regions with expansive rocky outcrops, in clearings, in burned areas or in small patches of sandy gravel. The eggs are not laid in a nest, instead laid on bare rock, gravel or sometimes a living substrate such as lichen
. Least popular are breeding sites in agricultural settings. As displayed in the latter portion of the 20th century, urban breeding is in decline. If urban breeding sites do occur; they are observed on flat, gravel rooftops.
It is a solitary nester putting great distances between other pairs of the same species, a nest would more commonly occur in closer proximity to other species of birds.
Females choose the nest site and are the primary incubators
of the eggs (males will incubate occasionally), incubation time varies but is approximately 18 days. The female will leave the nest unattended during the evening in order to feed. The male will roost in a neighbouring tree (the spot he chooses changes daily); he guards the nest by diving, hissing, wing-beating or booming at the sites. In the face of predation, Common Nighthawks do not abandon the nest easily; instead likely rely on their cryptic colouration to camouflage themselves. If a departure does occur the females have been noted to fly away, hissing at the intruder or to perform a disturbance display.
are elliptical shaped, strong, variably coloured with heavy speckling. The Common Nighthawk displays two, 6-7g, eggs per clutch
; the eggs are laid over a period of 1–2 days. The female alone displays a brood patch
.
The infants may be heard peeping in the hours before they hatch. Once the infants have broken out of the shells, there is a requirement to remove the debris in order to avoid predators. The mother may carry the eggshells to another location or consume a portion of them. Once hatched, the nestlings are active and have their eyes fully or half open, additionally they display a sparing cover of soft down feather
s. The infants are semiprecocial
. By day 2, the hatchling’s bodily mass will double and they will be able to self propel towards their mothers call. The young will hiss at an intruder.
The young are fed by regurgitation
before sunrise and after sunset. The male parent will assist in feeding fledgling
s and will also feed the female during nesting. No records exist to support the parent’s ability to physically carry a chick.
On their 18th day, the young will make their first flight; by days 25-30, they are flying proficiently. The young are last seen with their parents on day 30. Complete development is shown between their 45-50th day. At day 52, the juvenile will join the flock, potentially migrating. Juvenile birds, in both sexes, are lighter in colour and have a smaller white wing-patch, than adult Common Nighthawks.
in other geographical locations. The bird’s large range makes individual risk thresholds in specific regions difficult to establish.
The Common Nighthawk’s trait of being a ground nesting bird makes it particularly susceptible to predators some of which include domestic cats, ravens, snakes, dogs, coyotes, falcons and owls.
Lack of flat roofs, pesticides, increased predation and loss of habitat are noted factors of their decline. Further, unstudied potential causes of decline include climate change, disease, road kills, man-made towers (as an aerial hazard) and parasites.
The absence of flat roofs (made with gravel) in urban settings is a important cause of decline. In an effort to provide managed breeding areas, gravel pads have been added in the corners of rubberized roofs; this proves acceptable, as nesting has been observed.
Crepuscular
Crepuscular animals are those that are active primarily during twilight, that is during dawn and dusk. The word is derived from the Latin word crepusculum, meaning "twilight." Crepuscular is, thus, in contrast with diurnal and nocturnal behavior. Crepuscular animals may also be active on a bright...
or nocturnal bird, whose presence and identity are best revealed by its vocalization. Typically dark (grey, black and brown), displaying cryptic colouration and intricate patterns, this bird becomes invisible by day. Once aerial, with its buoyant but erratic flight, this bird is most conspicuous. The most remarkable feature of this aerial insectivore is its small beak belies the massiveness of its mouth. Some claim appearance similarities to owls
OWLS
OWLS is a mnemonic used by general aviation airplane pilots to assess an unprepared surface for a precautionary landing.Like all mnemonics this check has become part of aviation culture and folklore.OWLS:* Obstacles* Wind direction...
. With its horizontal stance and short legs, the Common Nighthawk does not travel frequently on the ground, instead preferring to perch horizontally, parallel to branches, on posts, on the ground or on a roof. The males of this species may roost together but the bird is primarily solitary. The Common Nighthawk shows variability in territory size.
This caprimulguid has a large, flattened head with large eyes; facially it lacks rictal bristles. The Common Nighthawk has long slender wings that at rest extend beyond a notched tail. There is noticeable barring on the sides and abdomen, also white wing-patches.
The Common Nighthawk measures 22-25 cm in length, displays a wing span of 21-24” / 54–61 cm, weighs 62-98 g, and has a life span of 4–5 years.
Taxonomy
Within family Caprimulgidae, subfamily Chordeilinae (Nighthawks) are limited to the New World and are distinguished from the subfamily Caprimulginae, by the lack of rictal bristles.The American Orinthologists’ Union treated the smaller Antillean Nighthawk
Antillean Nighthawk
The Antillean Nighthawk, Chordeiles gundlachii, is a nightjar.The adults are dark with brown, grey and white patterning on the upperparts and breast; the long wings are black and show a white bar in flight. The tail is dark with white barring; the underparts are white with black bars. The adult...
as conspecific with the Common Nighthawk until 1982.
Up until the early 19th century, the Common Nighthawk and the Whip-poor-will
Whip-poor-will
The Eastern Whip-poor-will, Caprimulgus vociferus, is a medium-sized nightjar from North and Central America. The whip-poor-will is commonly heard within its range, but less often seen because of its superior camouflage...
were thought to be one species. The latter’s call was explained as the nocturnal expression of the Common Nighthawk. Alexander Wilson
Alexander Wilson
Alexander Wilson was a Scottish-American poet, ornithologist, naturalist, and illustrator.Wilson was born in Paisley, Scotland, the son of an illiterate distiller. In 1779 he was apprenticed as a weaver. His main interest at this time was in writing poetry...
, “The Father of American Ornithology” correctly made the differentiation between the two species.
Subspecies
Chordeiles minor panamensis (Eisenmann, 1962)- breeds on
- Pacific slope of Panama and north west Costa Rica
- noted to depart Panama during winter for points in South America
Chordeiles minor neotropicalis (Selander & Alvarez del Toro, 1955)
- breeds in
- south Mexico
- Honduras
Chordeiles minor howelli (Oberholser, 1914)
- breeds in
- west central United States (north Texas, west Oklahoma, and Kansas to east Colorado, less typical form in central Colorado, north east Utah and Wyoming)
- darker than sennetti and paler and less cinnamon than henryi
Chordeiles minor hesperis (Grinnell, 1905)
- breeds in
- south west Canada (British Columbia and Alberta)
- western interior of United States (Washington, Montana, Nevada, interior California, Utah, extreme north Colorado, west Wyoming)
- darker than sennetti and paler and less cinnamon than henryi
Chordeiles minor aserriensis (Cherrie, 1896)
- breeds from
- south central Texas to north Mexico
- darker than sennetti and paler and less cinnamon than henryi
Chordeiles minor chapmani (Coues, 1888)
- breeds from
- South East Kansas to east North Carolina and southwards to south east Texas and south Florida
- darkest
Chordeiles minor sennetti (Coues, 1888)
- breeds in
- north Great Plains: east Montana, south Saskatchewan
- Manitoba, southwards to North Dakota, Minnesota and Iowa
- palest
Chordeiles minor henryi (Cassin, 1855)
- breeds from
- south east Utah and south west Colorado through mountains of west Texas, Arizona and New Mexico (less north east) to east Sonora, Chihuahua, and Durango
- unique with ochraceous to deep cinnamon feather edges on upperparts
Chordeiles minor minor (J. R. Forster, 1771)
- breeds from
- south east Alaska to Vancouver Island, British Columbia, Canada
- south Canada/northern United States (Minnesota, Indiana) to Virginia, North Carolina, Georgia and Oklahoma
- darkest
History
This species is recorded as widespread during the Late PleistoceneLate Pleistocene
The Late Pleistocene is a stage of the Pleistocene Epoch. The beginning of the stage is defined by the base of the Eemian interglacial phase before the final glacial episode of the Pleistocene 126,000 ± 5,000 years ago. The end of the stage is defined exactly at 10,000 Carbon-14 years BP...
, from Virginia to California and from Wyoming to Texas.
In the late 19th and early 20th century, because they held the title of "hawk
Hawk
The term hawk can be used in several ways:* In strict usage in Australia and Africa, to mean any of the species in the subfamily Accipitrinae, which comprises the genera Accipiter, Micronisus, Melierax, Urotriorchis and Megatriorchis. The large and widespread Accipiter genus includes goshawks,...
" in their names, had habits of diurnal insect hunting, and the fact that they travelled in migrating flocks, worked against these birds in that they were hunted for sport, nourishment and as predators.
Field Identification
The Common Nighthawk is distinct from other caprimulguids with its showing of a forked tail (includes a white bar in females); long, unbarred, pointed wings with a distinguished white patch; the lack of rictal bristles, and the key identifier – their unmistakable calls.The Common Nighthawk resembles both the Antillean Nighthawk
Antillean Nighthawk
The Antillean Nighthawk, Chordeiles gundlachii, is a nightjar.The adults are dark with brown, grey and white patterning on the upperparts and breast; the long wings are black and show a white bar in flight. The tail is dark with white barring; the underparts are white with black bars. The adult...
and Lesser Nighthawk
Lesser Nighthawk
The Lesser Nighthawk, Chordeiles acutipennis, is a nightjar found throughout a large part of the Americas.The adults are dark with brown, grey and white patterning on the upperparts and breast; the long upperwings are black and show a white bar in flight. The tail is dark with white barring; the...
. The Lesser Nighthawk is a smaller bird and displays more buffy on the undertail coverts, where the Common Nighthawk shows white. Common Nighthawks and Antillean Nighthawks exhibit entirely dark on the basal portion of the primary feathers, whereas Lesser Nighthawks have bands of buffy spots. Common Nighthawks and Antillean Nighthawks have a longer, outermost primary conveying a pointier wing tip than the Lesser Nighthawk. The Common Nighthawk forages higher above ground than the Lesser Nighthawk and has a different call. The Antillean Nighthawk may only be distinguished as different from the Common Nighthawk, once in the hand. Subtle differences are recorded to be a challenge in field identification.
Habitat and Distribution
The Common Nighthawk may be found in forests, desert, savannahs, beach and desert scrub, cities, and prairies, at elevations of sea level or below to 12000 ft / 3600 m . They are one of a handful of birds that are known to inhabit recently burned forests, and then dwindle in numbers, as successionEcological succession
Ecological succession, is the phenomenon or process by which a community progressively transforms itself until a stable community is formed. It is a fundamental concept in ecology, and refers to more or less predictable and orderly changes in the composition or structure of an ecological community...
al growth occurs over the succeeding years or decades. The Common Nighthawk is drawn into urban built-up areas by insects.
The Common Nighthawk is the only Nighthawk occurring over the majority of northern North America.
Food availability is likely a key factor in determining which and when areas are suitable for habitation. The Common Nighthawk is not well designed to survive in poor conditions, specifically low food availability. Therefore, a constant food supply consistent with warmer temperatures is a driving force for migration and ultimately survival.
It is thought that the bird is not able to enter torpor
Torpor
Torpor, sometimes called temporary hibernation is a state of decreased physiological activity in an animal, usually characterized by a reduced body temperature and rate of metabolism. Animals that go through torpor include birds and some mammals such as mice and bats...
, although recent evidence suggests the opposite.
Migration
Journey length 2500–6800 miles / 4000–11000 km.The Common Nighthawk will migrate by day or night in loose flocks; frequently numbering in the thousands, no visible leader has been observed. The enormous distance travelled between breeding grounds and wintering range displays one of the North America’s longer migrations. The north bound
journey commences at the end of February and the birds reach destinations as late as mid June. The south bound migration commences mid July and reaches a close in early October.
While migrating, these birds have been reported travelling through middle America, Florida, the West Indies, Cuba, the Caribbean and Bermuda, finally completing their journey in the wintering grounds of South America, primarily Argentina.
As aerial insectivore
Insectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
s, the migrants will feed on route, congregating to hunt in marshes, rivers and on lakeshores. In Manitoba and Ontario, Canada, it is reported that during migration the Nighthawks are seen most commonly in the late afternoon, into the evening, with a burst of sunset feeding activities.
Additionally, it has been noted that during migration the birds may fly closer to the ground than normal; possibly foraging for insects. There is speculation that feeding also occurs at higher altitudes.
The Common Nighthawk winters in the South Americas, but distribution in this locale is poorly known due to difficulties in distinguishing the bird from the Lesser Nighthawk
Lesser Nighthawk
The Lesser Nighthawk, Chordeiles acutipennis, is a nightjar found throughout a large part of the Americas.The adults are dark with brown, grey and white patterning on the upperparts and breast; the long upperwings are black and show a white bar in flight. The tail is dark with white barring; the...
and in differentiating between migrants and over wintering birds. In some South and Central American countries, a lack of study has led to restricted and incomplete records of the bird. Records do support wintering in Ecuador, Peru, Bolivia, Brazil, Paraguay, Uruguay and Argentina.
Moult
In the Common Nighthawk all bodily plumagePlumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
and rectrices are replaced in the post-juvenile moult
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...
. Post-juvenile moult commences in September at the breeding grounds; majority of the body plumage is replaced but wing-coverts and rectrices are not completed until January–February, once the bird arrives at the wintering grounds. There is no other moult prior to the annual moult of the adult. The Common Nighthawk adults have a complete moult that occurs mostly or completely on wintering grounds and is not ceased until January or February.
Vocalization
No differences between calls or song in the Common Nighthawk. The most conspicuous vocalization is a nasal peent or beernt during even flight. Peak vocalizations are reported 30–45 minutes after sunset.Croaking auk auk auk vocalized by males while in the presence of a female during courtship. Another courtship sound, thought to be made solely by the males, is the boom, created by air rushing through the primaries after a quick down flex of the wings during a daytime dive.
Hissing cluck heard by females, and wing-clapping by male during nest defence. Strongly territorial males perform dives against fledglings, females and intruders such as humans or raccoons.
Feeding and Diet
Frequent flyers, the long-winged Common Nighthawk hunts on the wing for extended periods at high altitudes or in open areas. Crepuscular, flying insects are its preferred food source. Cessation of the hunt as dusk becomes night, resumes when night becomes dawn. Nighttime (darkness) feeding is rare, even on evenings with a full moon. The bird displays opportunistic feeding tendencies, although it may be able to fine-tune its meal choice in the moments before capture.Vision presumed to be main detection sense. No evidence exists to support the use of echolocation. The birds have been observed to converge on artificial light sources in an effort to forage for insects enticed by the light. The average flight speed of Common Nighthawks is 23.4 kilometers per hour.
Drinking, Pellet-Casting and Droppings
The Common Nighthawk was observed to drink on its winter range by flying extremely low over the surface of the water.No evidence suggests this bird casts pellets.
The Common Nighthawk is recognized to discharge feces around nest and roosting positions. The bird will sporadically defecate in flight. Defecation is pungent.
Reproduction and Nesting
The Common Nighthawk breeds during the period of mid March to early October. It most commonly has a first and only broodBrood
Brood may refer to:* Brood, a collective term for offspring* Brooding, the incubation of bird eggs by their parents* Brood , the young of a beehive*Brood: to think deeply about something, often in a dark or melancholy manner....
, however sometimes a second later brood. The bird is assumed to breed every year. Reuse of nest
Nest
A nest is a place of refuge to hold an animal's eggs or provide a place to live or raise offspring. They are usually made of some organic material such as twigs, grass, and leaves; or may simply be a depression in the ground, or a hole in a tree, rock or building...
s by females in subsequent years has been reported. A monogamous pattern has also recently been confirmed.
Courting and mate selection occurs partially in flight, the male dives and booms (see Vocalization) in an effort to garner female attention, the female may be in flight herself or stationary on the ground.
Copulation occurs when the pair settles on the ground together; the male with his rocking body, widespread tail wagging and bulging throat expresses guttural croaking sounds. This display by the male is performed repeatedly until copulation.
The preferred breeding / nesting habitat is in forested regions with expansive rocky outcrops, in clearings, in burned areas or in small patches of sandy gravel. The eggs are not laid in a nest, instead laid on bare rock, gravel or sometimes a living substrate such as lichen
Lichen
Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
. Least popular are breeding sites in agricultural settings. As displayed in the latter portion of the 20th century, urban breeding is in decline. If urban breeding sites do occur; they are observed on flat, gravel rooftops.
It is a solitary nester putting great distances between other pairs of the same species, a nest would more commonly occur in closer proximity to other species of birds.
Females choose the nest site and are the primary incubators
Avian incubation
Incubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...
of the eggs (males will incubate occasionally), incubation time varies but is approximately 18 days. The female will leave the nest unattended during the evening in order to feed. The male will roost in a neighbouring tree (the spot he chooses changes daily); he guards the nest by diving, hissing, wing-beating or booming at the sites. In the face of predation, Common Nighthawks do not abandon the nest easily; instead likely rely on their cryptic colouration to camouflage themselves. If a departure does occur the females have been noted to fly away, hissing at the intruder or to perform a disturbance display.
Incubation, Hatching and Young
The eggsEgg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
are elliptical shaped, strong, variably coloured with heavy speckling. The Common Nighthawk displays two, 6-7g, eggs per clutch
Clutch (eggs)
A clutch of eggs refers to all the eggs produced by birds or reptiles, often at a single time, particularly those laid in a nest.In birds, destruction of a clutch by predators, , results in double-clutching...
; the eggs are laid over a period of 1–2 days. The female alone displays a brood patch
Brood patch
thumb|250px|Brood patch of [[Sand Martin]]A brood patch is a patch of featherless skin that is visible on the underside of birds during the nesting season. This patch of skin is well supplied with blood vessels at the surface making it possible for the birds to transfer heat to their eggs when...
.
The infants may be heard peeping in the hours before they hatch. Once the infants have broken out of the shells, there is a requirement to remove the debris in order to avoid predators. The mother may carry the eggshells to another location or consume a portion of them. Once hatched, the nestlings are active and have their eyes fully or half open, additionally they display a sparing cover of soft down feather
Down feather
The down of birds is a layer of fine feathers found under the tougher exterior feathers. Very young birds are clad only in down. Powder down is a specialized type of down found only in a few groups of birds. Down is a fine thermal insulator and padding, used in goods such as jackets, bedding,...
s. The infants are semiprecocial
Precocial
In biology, the term precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called "altricial," where the young are born or hatched helpless. Extremely precocial species may be called...
. By day 2, the hatchling’s bodily mass will double and they will be able to self propel towards their mothers call. The young will hiss at an intruder.
The young are fed by regurgitation
Regurgitation (digestion)
Regurgitation is the expulsion of material from the mouth, pharynx, or esophagus, usually characterized by the presence of undigested food or blood.Regurgitation is used by a number of species to feed their young...
before sunrise and after sunset. The male parent will assist in feeding fledgling
Fledge
Fledge is the stage in a young bird's life when the feathers and wing muscles are sufficiently developed for flight. It also describes the act of a chick's parents raising it to a fully grown state...
s and will also feed the female during nesting. No records exist to support the parent’s ability to physically carry a chick.
On their 18th day, the young will make their first flight; by days 25-30, they are flying proficiently. The young are last seen with their parents on day 30. Complete development is shown between their 45-50th day. At day 52, the juvenile will join the flock, potentially migrating. Juvenile birds, in both sexes, are lighter in colour and have a smaller white wing-patch, than adult Common Nighthawks.
Status and Conservation
There has been a general decline in the number of Common Nighthawks in North America, but some population increases also have occurredin other geographical locations. The bird’s large range makes individual risk thresholds in specific regions difficult to establish.
The Common Nighthawk’s trait of being a ground nesting bird makes it particularly susceptible to predators some of which include domestic cats, ravens, snakes, dogs, coyotes, falcons and owls.
Lack of flat roofs, pesticides, increased predation and loss of habitat are noted factors of their decline. Further, unstudied potential causes of decline include climate change, disease, road kills, man-made towers (as an aerial hazard) and parasites.
The absence of flat roofs (made with gravel) in urban settings is a important cause of decline. In an effort to provide managed breeding areas, gravel pads have been added in the corners of rubberized roofs; this proves acceptable, as nesting has been observed.
External links
- All About Birds, The Cornell Lab of Orinthology
- Chordeiles minor (Common Nighthawk), IUCN Red List of Threatened Species