Common nighthawks are medium-sized birds. They are 22 to 24 cm long and weigh 65 to 98 g. Like other members of the Caprimulgidae family, they have very large mouths and eyes. They are cryptically colored in many shades of brown. They have a notched tail and long, slender, pointed wings with white patches on the primary feathers. Males have a white tail band near the tip of the tail and a white throat patch. Females do not have a tail band and are more buff-colored on the throat. Both sexes have bold barring on the chest and belly, though the light parts tend to be whiter on males and more buff-colored on females.
Nine subspecies of common nighthawks have been described. These subspecies are separated by different colors in their plumage. Common nighthawks are often confused with two very similar species of nighthawks: Lesser nighthawks (Chordeiles acutipennis) and Antillean nighthawks (Chordeiles gundlachii). (Ehrlich, 1988; ; Poulin, et al., 1996)
Common Nighthawks (Chordeiles minor) breed throughout much of North America and parts of Central America. Their winter distribution is less well known, but they are believed to range throughout middle South America in the lowlands east of the Andes. (; Poulin, et al., 1996)
Common nighthawks breed in open habitats such coastal dunes and beaches, woodland clearings, grasslands, savannas, sagebrush plains, and open forests. They will also use human habitats, such as logged or burned areas of forests, farm fields, and cities.
Common nighthawks choose nest sites on the ground in open areas with some cover from grasses, shrubs, logs, or boulders. They do not build nests. Instead, they lay their eggs directly on the sand, gravel, leaves or bare rock that cover the ground. Common nighthawks sometimes nest on flat gravel roofs of houses.
Little is known about the migration routes or winter habitat of common nighthawks. They have been seen migrating across wetlands, farmland, river valleys, open woodlands, and coastal dunes. They probably prefer open areas for their wintering grounds. (; Poulin, et al., 1996; Stiles and Skutch, 1989)
There is little information available about the mating system of common nighthawks. Males court females by displaying on the ground and in flight. They begin by flying 5 to 30 meters into the air and then diving steeply toward the ground, pulling up sharply about 2 meters above the ground. This display is accompanied by a “booming” noise made by the air rushing through the primary feathers of the male. Males then land near the female, spreading and shaking their tail from side to side, displaying their white throat patch, and making a croaking noise.
Southern populations of common nighthawks may produce chicks as early as May, while northern populations may not produce young until August. Little is known about how breeding pairs form, or about their breeding activities. Female common nighthawks arrive first at the breeding grounds and choose the nest site. Some of return to the same nest sites every year. Common nighthawks probably breed once per year. We do not know how old they are when they first breed.
Females usually lay 2 eggs, 1 to 2 days apart. The eggs are pale, splotched with gray, brown, and black. The female incubates the eggs for 18 to 20 days, leaving the nest in early evening to feed. After the eggs hatch, the female continues to leave the nest to forage in the evening. She feeds regurgitated insects to the chicks before sunrise in the morning and after sunset in the evening. The nestlings are semiprecocial and can move themselves if called by the female when they are just a day old. The young can move themselves to shade or sun to regulate their body temperature. After 16 days, young can hop. At 18 days old, they make their first flight, and can fly well at about 25-30 days old. By the time they are 30 days old, chicks have left the nest for good. They are fully grown 45-50 days after hatching, and probably join migrating flocks at that time.
In southern parts of the breeding range, breeding pairs may have a second brood. If this happens, the male feeds the young of the first clutch while the female incubates the second clutch. He will also feed the female. (; Poulin, et al., 1996)
The female of a breeding pair incubates the eggs and broods the young chicks. She may also move them around to put them into nearby shade. The parents feed the chicks regurgitated insects until they are able to feed themselves at age 25 days or so. The male defends the nest site by beating his wings and hissing at intruders. The female may also defend the nest site by hissing or pretending to be injured. (; Poulin, et al., 1996)
Common nighthawks are expected to live at least 4 to 5 years. The oldest known wild common nighthawk was 9 years old. (; Poulin, et al., 1996)
Common nighthawks are some of the last migratory birds to arrive at their breeding grounds in the spring, and some of the first to leave in fall. This is probably because they eat insects, which are only available during warm weather. Some birds are able to go into torpor on cold nights, a behavior that helps them conserve energy. Common nighthawks are not able to do this, so they are sensitive to cold temperatures.
Common nighthawks migrate 4,000 to 11,000 km (2,500 to 6,800 miles). This is one of the longest migrations of any bird in the Americas. They migrate in flocks, especially in the fall. Most pass through Central America, but some cross the Gulf of Mexico and the Caribbean. During migration, common nighthawks may ride thermal currents like migrating hawks.
Common nighthawks are very territorial, solitary nesters. Males defend their territory by diving and hissing at intruders. The territory size of common nighthawks is different in different habitats, but ranges between 41,000 and 280,000 square meters. When they are not at the nest, common nighthawks roost, sleep, or sunbathe on fence posts, tree branches, the ground, or flat rooftops. Common nighthawks are crepuscular.
Bats and lesser nighthawks have been seen chasing common nighthawks away from common feeding spots. Common nighthawks may not be able to feed at spots with lesser nighthawks because the lesser nighthawks are so aggressive toward them. (Elphick, 1995; ; Poulin, et al., 1996)
Common nighthawks use calls and displays to communicate with one another. The vocalizations of common nighthawks are very simple, and have few variations. They also use non-vocal sounds, such as the booming sound made by the primary feathers of males during a courtship display to communicate. An example of the physical displays used by common nighthawks is the diving display given by males to prospective mates. (; Poulin, et al., 1996)
Common nighthawks are crepuscular. They are most active at dawn and dusk, but occasionally feed during the day in low light conditions, like stormy weather or fog. They use their wide mouths to “hawk” insects in the air. Their large eyes help them find and distinguish among prey items in the dark. They also have a tapetum, a mirror-like structure at the back of each eye that reflects and helps them see in the dark. They fly around, changing directions quickly, and eating up 50 different insect prey species. Most of their prey species are queen ants (Hymenoptera), beetles (Coleoptera), and true bugs (Homoptera). It also includes moths (Lepidoptera), mayflies (Ephemeroptera), caddisflies (Trichoptera), flies (Diptera), wasps (Hymenoptera), crickets and grasshoppers (Orthoptera) and other insects. In urban areas, common nighthawks often fly around streetlights or bright yard lights, catching insects that are attracted to the light.
Common Nighthawks drink while in flying by skimming the surface of lakes, streams, or water troughs with their bills. (Brigham and Barclay, 1995; Brigham, 1990; Nicol and Arnott, 1974; ; Poulin, et al., 1996; Terres, 1980)
Females and young rely on their cryptic brown coloration to hide them from predators. Males do not guard the nest but will defend it by diving over it and booming with their wings or beating their wings and hissing. Females may pretend to be injured to distract predators and keep them away from the nest. Chicks also defend themselves by spreading their wings and hissing at intruders. (; Poulin, et al., 1996)
Common nighthawks have no known negative impact on humans.
Since common nighthawks are insect eaters that frequent farm fields and cities, it is likely that they help control pest insect species.
Populations of common nighthawks are declining. This is probably the result of many different human activities. Pesticides used in cities and on farms poison common nighthawks. The gravel roofs that many common nighthawks nest on are being replaced by rubber roofs. Common nighthawks that nest in cities are also in danger of predation by housecats and other species. Common nighthawks are sometimes killed by vehicles when roosting or feeding along roadways. (Poulin, et al., 1996)
Common Nighthawks are known for their loud, nasal “peent” calls made by both sexes, as well as the males’ amazing, booming courtship dives. My husband and I were equally freaked-out and captivated by their mysterious sounds one summer night in eastern Arizona. We were driving home from Colorado, and the sun had long-since gone down. Eyelids heavy, we pulled off onto national forest land just east of Show Low to camp for the night. We laid our tarp and sleeping bags on rough volcanic gravels in a sparse juniper woodland. There was no moon. Just as we had fallen asleep, we were awaken by a loud “peenting” noise, followed by a booming, zipping “woosh.” It passed right over our heads. A few seconds later, the peent came again from a completely different corner of the sky, followed by another close woosh above our heads. Our first thought was that bored teenagers from Show Low had somehow found our campsite and were messing with our minds. What WAS that sound?!? Strangely muffled gunshots? UFO’s landing? A huge bug-zapper? It just didn’t sound natural. How could something be in one spot, then abruptly be 200 meters away, making such a mechanized sound? Then, the sound ceased, leaving us to wonder its origins. We drifted off to sleep, only to be awoken a while before dawn.
Peent! Woosh! Silence. Peent… again from a spot impossibly distant from the first call…and woosh above our heads. Disbelief gave way to reason as we hunkered in our bags, commiserating: “It’s got to be a bird.” “Maybe some kind of nightjar?” Sure enough, as the sun gradually lightened the eastern sky, we began to make out an avian shape. It would flap up on slender, pointed wings, hover, give out a loud “peent”, and dive steeply. The mechanical woosh and zipping noise came with the dive and ceased with the bird’s abrupt return skyward. It would peent again a couple hundred meters from where it began its last dive, then plunge downward. Boom-woosh! As the sky lightened, we saw the flash of white wing-patches on a second bird – perhaps a female? Then they moved off and were gone. We consulted our bird books later and decided they must have been common nighthawks. Could they have been courting? Were we disturbing a nest site? We’ll never know. Though no records of nighttime diving displays exist for this species, we definitely witnessed them late into the night and well before dawn. An unforgettable experience!
Kari Kirschbaum (editor), Animal Diversity Web.
Robin Kropp (author), University of Arizona, Jorge Schondube (editor), University of Arizona.
Brigham, R. 1990. Prey selection by big brown bats (Eptesicus fuscus) and Common Nighthawks (Chordeiles minor). American Midland Naturalist, 124: 73-80.
Brigham, R., R. Barclay. 1995. Prey selection by Common Nighthawks: does vision impose a constraint?. Ecoscience, 2(3): 276-279.
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Elphick, J. 1995. Atlas of Bird Migration. London: Harper-Collins Publishers, Ltd.
Nicol, J., H. Arnott. 1974. Tapeta lucidum in the eyes of goatsuckers (Caprimulgidae). Proceedings of the Royal Academy of London, 187: 349-352.
Poulin, R., S. Grindal, R. Brigham. 1996. Common Nighthawk (Chordeiles minor). A Poole, F Gill, eds. The Birds of North America, Vol. 213. Philadelphia, PA and Washington DC: The Academy of Natural Scientists and The American Ornithologists Union.
Stiles, F., A. Skutch. 1989. A Guide to the Birds of Costa Rica. Ithaca: Cornell University Press.
Terres, J. 1980. The Audubon society encyclopedia of North American birds. New York: Alfred A. Knopf.