National Geographic : 1932 Jul
THE NATIONAL GEOGRAPHIC MAGAZINE NIGHTHAWK (Chordeiles minor) In a family whose members are known princi pally as voices of the night, the nighthawk is the most frequently seen and most familiar, since, though it shares the nocturnal habits of its rela tives, it is also regularly abroad by day, when its long-winged form is prominently seen, as it quar ters the sky in its migrations or in search for food. Its common name is given from its hawklike ap pearance when on the wing, a resemblance that is entirely superficial, since it has no close affinity with the falcons and their relatives. The specimen figured is a male, the female differing principally in the lack of the white bar across the tail. The white mark across the wing is prominent when the bird is in flight. The nighthawk is largely a bird of the open country, being partial to open pastures, plains, and prairies, where it rests on the ground, on stones, stumps, and fence posts and at times in trees. In the latter case it always perches length wise of the limbs, like its near relatives. In wooded country it ranges in the borders of the forests where the tree growth is open. The food of the nighthawk is composed en tirely of insects, including almost everything in this group that flies, ranging from the largest moths and dragon flies to mosquitoes and tiny gnats. The food is captured entirely on the wing, during the intricate aerial evolutions for which these birds are famous, the prey being gathered in the widely opened mouth, which, though it lacks the long rictal bristles found in its relatives, is highly effective as a net or scoop. Some of the gatherings of small insects secured by these birds are truly remarkable, as several thousand individuals, including more than 50 species, have been found in the stomach of one nighthawk. Flying ants are eaten in large quantities, and these birds on the whole are de cidedly beneficial in their destruction of injurious insects. The nighthawk nests on gravel bars, sand spits, in pastures, particularly in rocky soil, and in sim ilar locations, placing its two eggs in the open, in some slight depression, on the bare ground. With the development of modern cities, the flat, gravel covered roofs of tall buildings have provided suit able sites where the birds may nest in safety, with the wide sky overhead as a feeding ground-an interesting adaptation to change in condition brought by modern civilization. The eggs vary from cream to olive gray, blotched and speckled with blackish brown and lavender. In the mating and nesting season the male nighthawk indulges in rapid, erratic flights, which terminate in a thrilling downward plunge at high speed with stiffly set wings. As this rapid course is suddenly checked, the vibration of the air through or against the flight feathers produces a vibrant, roaring sound that may be heard for a considerable distance. Formerly this species, under the name of "bull-bat," was shot for sport, a practice that now is prohibited by law. The nighthawk as a species ranges from Yukon, Mackenzie, and Newfoundland south into north ern Mexico, the Bahama Islands, and the Greater Antilles. In winter it travels south into South America. Nine geographic races, differing in size and color, have been recognized, of which seven occur in our limits. TEXAS NIGHTHAWK (Chordeiles acutipennis) In general appearance this bird resembles the ordinary nighthawk, from which it differs in being slightly smaller and in having the white bar on the wing located nearer the tips of the primaries. When seen close at hand, it has a distinctly browner appearance. The Texas nighthawk is found in the warmer sections of the Southwest, being especially partial to desert areas, where it may live and nest many miles from the nearest water. It is most active during early morning and late evening, being seldom on the wing during the middle of the day, unless disturbed by some intruder, when it flies without confusion, seeming unaffected by the light. It rests on the ground, or on low branches of mesquite or greasewood, in the latter case perching always lengthwise of the branches. On the ground, it moves about to some extent, and when disturbed frequently raises the head and neck and moves the body up and down. The flight of this nighthawk is easy and grace ful, but the birds ordinarily remain near the ground, not rising as high in the air as the related species. The wing motion is somewhat quicker and less vigorous than in the larger nighthawk. The Texas nighthawk in courtship indulges in display flights in which the birds pursue one an other quickly, the males at times sailing with the wings held stiffly decurved at an angle below the level of the body. Their ordinary call is a mel low, rolling trill, given when the bird is on the ground or flying, that may be continued for many seconds. It utters a variety of whining, com plaining notes in addition, but does not produce the booming sound peculiar to the courtship of its larger cousin. The two eggs are laid on the open ground, without nesting material, ordinarily where there is not the slightest shelter from the blazing sun. The eggs are pale gray to light cream color, mi nutely marbled, and spotted with shades of gray and lilac, with a few bolder markings of slate and brown. Occasionally an egg is found with only a few very minute markings. All are paler-colored than in the other nighthawk. Within a day or two after hatching, the young are able to crawl about and move from place to place over the nesting area, selecting sections of partial shade, where they get some protection from the sun. Both eggs and young are so closely similar to the ground on which they rest that they . are not easily detected, being even difficult to see when their exact location is known. It is reported that this species in some locali ties has begun to nest on the flat tops of low adobe houses, so that it is showing an adaptation to the encroachment of man in its haunts. The true Texas nighthawk (Chordeiles acuti pennis texensis) nests in the Lower Austral Zone from north central California, southern Utah, and central Texas south to about latitude 30° in Lower California, and to south central Mexico. It is found in winter casually in southwestern Arizona and regularly from central Mexico to Panama. A related race. the San Lucas night hawk (Chordeiles acutipennis inferior), occurs in Lower California from about latitude 30° south. Another form is found in southern Mex ico, Guatemala, and Honduras.