October 2017

Vol. 45, No. 5

Front Cover: October 2017

Common Nighthawk by John Sill

Common Nighthawk by John Sill ©Massachusetts Audubon Society. Courtesy of the Museum of American Bird Art.

John Sill is a freelance wildlife artist living in the mountains of North Carolina. He was the illustrator for the Bird Identification Calendar for Mass Audubon for many years. His work has appeared in Birds In Art at the Leigh-Yawkey Woodson Art Museum, Wausau, Wisconsin, and in Art of the Animal Kingdom at the Bennington Center for the Arts in Vermont. He continues to illustrate the “About” and “About Habitats” series of natural history books for children written by his wife Cathryn.

Common Nighthawk

The Common Nighthawk (Chordeiles minor) was once a frequent sight on hot summer nights hawking insects at ballparks or other well-lighted events. When perched, it is a brown to buffy or gray bird with a large flat head, a large mouth, and large eyes. It is finely-striped dark brown on buff or gray below; and its upper parts are mottled shades of brown, buff, and grayish white with a whitish throat patch. Its wings are long and pointed, and they protrude beyond the tail. Sexes are similar in appearance, although females and juveniles tend to be buffier overall.

At rest, the Common Nighthawk can be confused with other caprimulgids, but in flight its pointed wings with white wing patches distinguish it from the Whip-poor-will, Chuck-will’s-widow, and Common Poorwill. It also lacks the rictal bristles of these other species. The Lesser Nighthawk also has a white wing patch but it is located closer to the tips of the primaries. If they are silent, separating caprimulgid species at rest can be a real challenge. Nine nighthawk subspecies are recognized with only C. m. minor found in our area. The Common Nighthawk is closely related to the Antillean Nighthawk of south Florida, the Bahamas, and the Greater Antilles and can only be distinguished from it by voice. The two species were considered conspecific until 1982 when they were split, mostly because the call of the Antillean, killikidick, is so different from the peent of the Common Nighthawk.

Common Nighthawks breed from the Yukon across Canada, dipping below Hudson Bay to southern Labrador and Nova Scotia and south throughout the United States except for parts of California, Nevada, and Arizona. In Mexico, the species breeds in a long belt in the inland west and along the east coast. Breeding is patchy throughout Central America. The entire breeding population is migratory to South America, but the wintering distribution is poorly known. In Massachusetts, the Common Nighthawk is today considered a rare and local breeder. It is an uncommon spring migrant during May and June and occasionally abundant during fall migration toward the end of August and early September.

Little is known about the biology of this cryptic species, including its breeding system. The Common Nighthawk is presumed to be monogamous. The call or song peent is given by both sexes in flight. The male gives the call during his mating or “booming display” in which he dives and the air rushing through the primary feathers produces a booming sound. The dive begins at heights up to 100 feet and the bird pulls up within 10 feet of the ground. During courtship on the ground, the male spreads his tail, puffs his throat to display his white throat patch, rocks his body, and utters a croaking sound. The booming display is also used in territorial advertisement. Common Nighthawks will dive on almost anything that enters their territories, including humans.

Nesting habitat is varied, from coastal dunes and beaches to prairies, agricultural lands, grasslands, burned-over forest, and urban areas on gravel-topped flat roofs of buildings. The female selects the nest site, usually in the open but often near rocks, logs, or shrubs. Common Nighthawks often roost and occasionally nest atop fence posts. No nesting material is used and the nest substrate may vary from bare rock or wood to leaves or lichens. The female may use the same nest site for more than one year. Only the female develops a brood patch and in most cases she alone incubates the clutch of two creamy white to gray, heavily spotted eggs for the two-and-one-half to three weeks until hatching. The chicks are semi-precocial: covered with sparse down, their eyes are half-open or open at hatching, and they can hold their heads up almost at once. They can move short distances when two days old. The young are fed regurgitated insects, mostly by the male, who also feeds the brooding female. Adults offer a variety of distraction displays including flying off and settling within sight of the intruder, sometimes with wings drooping or outstretched, which is often referred to as false brooding. The young birds are capable of flight after three and one half weeks and in about seven weeks join migrating flocks of other nighthawks.

Common Nighthawks forage in flight, mostly at dawn and dusk. They are visual foragers, and their large eyes are almost certainly an adaptation to crepuscular feeding. Opportunistic foragers, they are prone to taking advantage of artificial lights that attract insects, such as streetlights or the bright lights at sporting events. They almost exclusively take flying insects. Their erratic, batlike flight while foraging has earned them the moniker “Bullbat.”

Little is known of predation in Common Nighthawks. Being primarily ground nesters, they are subject to nest predation by the usual mammals and birds. Hawks and owls prey upon adults. Breeding Bird Survey (BBS) data suggest serious decline in numbers across their range during the second half of the 20th century, but the data are somewhat soft because it is difficult to census nesting cryptic caprimulgids. Curiously, however, a half-dozen or so states have reported increases in Common Nighthawk numbers. Many factors have been suggested to account for the general decline in nighthawk numbers, including a shift in the construction from gravel to smooth, rubberized flat-top roofs, pesticides that reduce flying insect numbers, and collisions with cars where nighthawks forage low enough to get struck. Until we have better methods for determining population changes for this cryptic species, its true status will remain uncertain. The broad breeding and habitat range of this unique species will hopefully ensure its continued survival.

William E. Davis, Jr.

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