On late spring or summer walks, have you ever looked up after hearing nasal, piercing “peent” calls high in the sky? Those calls used to be common fare on summer evenings and nights. Glancing up, you might see a stream-lined, medium-sized bird with angular wings sculling through the air, quickly and erratically. Wheeling around after flying insects, common nighthawks, Chordeiles minor, are often heard before they’re seen. To a casual observer they might look like bug-catching bats.

The name “nighthawk” probably came from a vague resemblance to small hawks, but common nighthawks are more closely related to owls. They belong to the Nightjar family, with the scientific name Caprimulidae, which means “goatsucker.” That name myth traces back to superstitious goat-herders in ancient Greece. They saw night birds fluttering around their animals open-mouthed, and believed the birds came in the dark to drink milk. It wasn’t true, but the name stuck anyway.

Armed with large eyes, wide mouths and small beaks, nighthawks usually take to the air when twilight descends. They hunt throughout the night until dawn. At least one member of this bird family employs sonar echoing to catch insects in a manner similar to bats. They also chase insects and bugs on cloudy days, especially after rainy nights that render hunting impossible. When flying, nighthawks can be identified by a white bar on the underside of each long, pointed wing.

Common nighthawks range across Canada as far north as the Yukon and Labrador in summer, and in winter as far south as Argentina. That makes their migration one of the longest of any North American bird. Their tiny feet are awkward for walking, but fine for perching. During the day these birds normally roost perched lengthwise on an elevated tree limb, rather than at right angles to it. This orientation could be part of their “dead leaf” camouflage disguise. They also roost on the ground or on fence posts.  Equipped with toes that have partial webbing, their middle toe is pectinate (comb-like), for feather grooming.

Other members of the Nightjar family in eastern Canada include the Eastern whip-poor-will, Antrostomus vociferous, and the Chuck-will’s widow, Antrostomus carolinensis.

Courting and nesting rituals
Nighthawks usually arrive from their winter home in South America in May, about the time insects become abundant. They feed upon moths, grasshoppers, beetles, flies, mosquitoes, and flying ants while foraging in flight. One nighthawk stomach examined in Maine had 2,175 flying ants. Another in Massachusetts had eaten more than 500 mosquitoes. Sometimes they even pick up water in their beaks while skimming the surface of streams and lakes. 

Males make a spectacular aerial display and so-called “booming” sound at mating time. To impress the female, a hopeful male flies upwards 50 to 60 metres until he’s a speck in the sky, circles and utters nasal peenting calls. This behaviour is similar to the breeding sky dance of male woodcocks. Then he suddenly plunges, streaking towards the ground. At the last moment, he breaks the dive and swoops up. During the turn he twists his wings in such a manner that air is forced through flight feathers, emitting a loud, muffled “woof” or booming sound. This sound is thought to have courtship as well as territorial functions, like bird breeding songs, and it usually happens over the “nest” area. After each display, he will land near his intended, spreading his tail and rocking back and forth, while calling to her. How can a female nighthawk resist such prowess?

Common nighthawks do not actually build a nest. Rather, one to three spotted eggs are normally laid, beginning in early June, on unprepared, flat ground that can be sand, pebbles, forest leaf litter, a recent burn, or even the gravel of flat-roofed buildings.

It’s rare to find a nighthawk ground site when they are incubating eggs.  I’ve only located a handful of those in more than five decades of conducting woodland wildlife inventories in Nova Scotia.   

A nighthawk on the ground during the day is virtually invisible. Their feathers are cryptically-coloured in intricate patterns of browns and grays that are a perfect match for ground covers in a variety of open or semi-open habitats that the birds prefer. Typical sites include clearings in evergreen or deciduous forests, open pine woods, farmlands, suburbs, and even cities, towns, and villages. In human settings, they usually lay eggs on flat gravel rooftops. Killdeer are another bird species that will nest on such a roof.

The parents incubate and periodically move their eggs around for three weeks until they hatch. They then brood them against heat, cold, and rain, while defending them from predators such as raccoons and dogs. The pair feed the hatchlings regurgitated insects for another three weeks. The young are precocious, ready to walk away to avoid predators minutes after they are born. Youngsters continue to solicit food from the parents and often show little interest in flying. By early July, parents can be seen with well-developed young. The adults sometimes hold back food to inspire them to fly.

By late August, insects are on the wane, and both young and old are preparing to fly to South America. 

Population status
Declines in Maritime populations and other populations throughout most of its North American range prompted the Committee on the Status of Endangered Wildlife in Canada to list the common nighthawk as threatened in 2007. In Eastern Canada, many insect-eating species like swallows and swifts are also in decline. It’s easy to note the change in insect populations if you remember the summer bug smears that used to appear on windshields decades ago.   

For no good reason, 100 years ago these fall migrants were used as targets by local hunters and large numbers were shot annually. Legal protection and public opinion in favour of the birds ended this wanton killing.

The reasons for current nighthawk population declines are linked to climate change. Their migration arrival here is timed to the emergence of insect populations. Populations of the insects they consume are being disrupted by climate change, with its extreme weather. The timing of insect emergence and nighthawk arrivals here may no longer be synchronized. Nighthawks are also affected by insecticide use, road kills, air pollution, and loss of open habitats. Increased predation from species like raccoons, skunks, dogs, and crows could also be influencing their demise.

Grazing animals, small-scale logging operations and forest fires create nesting and roosting habitats. Adding gravel on top of rubberized roofs enhances the chances of their nesting in urban areas.

Nighthawks can be seen overhead in much of Atlantic Canada. Although they are rare in the Cape Breton Highlands and over much of P.E.I., elsewhere they can be seen gathering to leave for the south in September and October. Whenever I hear them while hiking or canoeing, I look up to watch their “SWAT team” aerial acrobatics. And appreciate their mosquito control!