Posted By William LeRoy on Jun 29, 2015

Arizona’s Mystery Bird

By William Leroy for Wild At Heart

Lesser Nighthawk

If you are lucky enough to be a full time Arizona resident, and spend any time outdoors in the summer evenings, then you have probally seen a Lesser Nighthawk on the wing. The Lesser Nighthawk, formerly known as the Texas or Trilling Nighthawk, is a little-studied, desert-dwelling bird of the Arizona Sonoran Desert, the American Southwest and Central and South America. Although not much is known about their specific migratory routes or the timing of their migrations, we do know that these birds typically arrive here in Arizona from South and Central America sometime between March and the end of May. They begin to return home in late August and seem to be removed from our State by the end of October.

Description

A slender, small to medium-sized bird, length 20–23 cm; wingspan 55 cm; mass about 45 g. All plumages cryptic, rendering birds almost invisible perched on the ground. Upperparts of adult male gray brown, mottled with buff, brown, and blackish; throat has prominent white, V-shaped patch; chest mottled dark gray and brown; underparts buff, with dusky, dark brown barring; tail slightly notched, blackish tip, barred sandy, with subterminal white band; wings slender, pointed, with white patch across distal portion of outer 4 primaries that is conspicuous during flight; wing-coverts mottled gray brown. Female similar to adult male but smaller; also lacks subterminal tail-band and has smaller, buffy white wing-patch. There is no seasonal plumage change.

Lesser Nighthawk

Hunting

The Lesser Nighthawk obtains nearly all of its food in flight. It will typically captures aerial insects in scoop of its open mouth. They will generally forage at dusk and dawn, and sometimes hunts at midday, especially in cloudy weather. They may also fly on moonlit nights. Lesser Nighthawks roam over considerable distances in search of food and water, seeking insect swarms wherever available; often attracted to insects that gather around bodies of water or lights, but may also appear near pole lights in town plazas, over roads, and in open areas. May forage higher in air at sunset, then lower as light diminishes, and also hunts from the ground, perching on quiet roads or in desert scrub, perhaps seeking insects attracted to retained heat, then bursting up without taking flight to snap up a passing insect. If you head into Cave Creek or Carefree for an evening out, you can generally see groups of Lesser Nighthawks flying around the light poles hunting insects in the quieter parking lots of off the beaten track restaurants like the Horny Toad (for example). I have seen them around arena lights out here in the Rio Verde Foothills as well (in addition to the sunset twilight hours).

Family Life

Little is known about the breeding season, what has been observed shows that the Lesser Nighthawk lays its eggs on bare, flat ground, in areas often strewn with pebbles, but without nest material. Sites include rocky country, parched gravelly mesas, lowland hills, gravel streambeds, vineyards or other agricultural areas, alkali barrens in North America, and savannas and debris-strewn beaches in Central America. Also nests on adobe or other roofs in Arizona and New Mexico. On Brazil (e. Amazonia), nests have been found along the edge of a little-used gravel road. Most often the nests are located in the full sun, but sometimes they are also found in partial shade, usually on north side of small bushes or beneath overhanging branch. Other nests have been found beneath creosote bushes, greasewood bushes and alkali blite.

How the Lesser Nighthawks care for their eggs is fascinating. Even though the eggs are placed on the bare ground and in direct sunlight, the egg temperatures are maintained below lethal levels by 100% attentiveness of incubating female. Females sit tightly on the nest throughout the day without relief or going to water. The Lesser Nighthawks are thought to possess abdominal air sacs closely underlying the female’s abdominal wall that may help cool the eggs slightly if eggs are positioned near these sacs. An alternative egg-cooling strategy may be that female’s gular-flutter at temperatures lower than the 42°C. Lesser Nighthawks will also use natural shade to cool eggs temporarily, but may generally avoid shade, as an anti-predator strategy. At the Salton Sea, females nesting near shade sometimes move eggs up to 15 cm to take advantage of shade in the heat of the day, and then return eggs to their original position later in the day. Upon birth, the father is primary provider of food to young. Parents feed the young by regurgitating a ball of insects held together with sticky saliva. Adult thrusts bill into opened mouth of young, and uses muscle contractions to bring forth food. Young nesting Nighthawks are capable of walking 1–2 day after hatching; and after this, have been observed moving about within 10–20 meters of the nest or the position they occupied the previous day. Nothing else is known about their young adult lives.

Interesting Facts

• Lesser Nighthawks catch flying insects on the wing, mainly foraging near dawn and dusk (crepuscular), sometimes at night with a full moon or near street lighting.
• Adults flushed from the nest may try to distract the intruder or defend the nest site by aerial attack.
• Young birds sometimes perform a defense display by opening up their mouths and spreading their wings, looking to appear threatening and looking larger than they actually are before they run off.
• A group of nighthawks are collectively known as a “kettle” of nighthawks.
• Lesser Nighthawks have unusual physiological tolerances, especially in relation to heat and cold. In the summer, nesting individuals are exposed to extreme heat and often gular-flutter to enhance evaporative cooling. This behavior, combined with other behavioral traits, contributes to an unusually effective capacity for temperature regulation in hot environments. Although migratory, Lesser Nighthawks are capable of responding to cold weather and depressed food resources by remaining torpid for relatively long periods in a manner reminiscent of hibernating mammals.
• As an adaptation to aerial feeding, the Lesser Nighthawks gape is large and edge of mouth is lined with hair like bristle feathers that form a sort of insect sweep-net.
• Lesser Nighthawks have been found to ingest stones, which are retained as grit in their stomachs, presumably to help grind the heavy, chitinous bodies of beetles that form large part of their diet.

Status in the Wild

The Lesser Nighthawk is evaluated as Least Concern at this time. This terrestrial bird species is native to South America, North America and Central America. The range of the Lesser Nighthawk is more than 2 million square kilometers. The population of this bird species is nearing 6 million individual birds. Thankfully, at this time the Lesser Nighthawk is not facing any immediate threats or dangers.

About Wild At Heart

Wild At Heart is an all-volunteer organization which is dedicated to the conservation and preservation of Arizona’s native wildlife. At Wild At Heart we: Rescue, rehabilitate, and release birds of prey which have been injured or orphaned. Relocate displaced burrowing owls. Manage species recovery programs. Manage habitat enhancement projects. Provide educational presentations. Each year, Wild At Heart rescues and cares for approximately 400 owls, hawks, and falcons, and some years, as many as 600 raptors have been cared for in the facility. Every single dollar donated goes towards the rescue, rehabilitation, care and release of our amazing Arizona Birds of Prey.

Wild At Heart is an all-volunteer non-profit 501(c) 3 organization. Support for Wild At Heart comes from generous members of the community who are concerned about our ever-decreasing wildlife habitats.

Please send your tax-deductible donations to “Wild At Heart” at the following address: Wild At Heart, 31840 N. 45th Street, Cave Creek, Arizona. 85331. For additional information regarding how you can support Wild At Heart please go to: http://www.wildatheartowls.org/   Visit Website