National Geographic : 1932 Jul
THE NATIONAL GEOGRAPHIC MAGAZINE BLACK SWIFT (Nephoecetes niger borealis) In the United States the black swift is local in occurrence and is counted as one of our rarer and more unusual birds throughout much of its range. While in dark coloration it resembles the chimney and Vaux's swifts, it is larger, and when size is not a sufficient criterion may be told by the longer, narrower wings and the decidedly longer, forked tail. Like all its relatives, it is entirely at home in the air and is usually seen darting and turning high above the earth. Though ordi narily silent, at times it utters loud, chirping calls that may be modified to a rolling twitter. Usually it is found in little flocks. For many years the nesting of this species re mained a mystery, until it was found breeding on cliffs above the sea, in southern California, on small shelves, where the single white egg was placed on a slight depression, on moist sod. In the Yosemite nests have been found on cliffs in mountain gorges, built of fern leaves to form a cup. It is believed that these swifts may nest also in hollow trees, but this has not been definitely established. This form of the black swift is found from southeastern Alaska and southern Colorado to southern Mexico, wintering in the southern part of its range. An allied form occurs in the West Indies, where in places it is very abundant, being found at times in groups containing hundreds of individuals. CHIMNEY SWIFT (Chaetura pelagica) This species, known to many as the chimney "swallow," from its swallowlike form, is one of the well-known summer birds of the eastern half of our country. In pairs and trios, with rapidly moving wings, these birds pass swiftly overhead, with chirping, twittering notes that at times in crease in rapidity of utterance, so that they almost become a song. In the early days in our country this swift inhabited hollow trees, but with the advent of the white man's houses it began to occupy chimneys, until now, though the birds are found occasionally in ice houses or other dark buildings, it is exceptional for them to live in tree trunks. They never perch except on the in side of a chimney, hollow tree, or on a wall. The nest of the chimney swift is formed of small twigs cemented together by a salivary secre tion to form a semicircular saucer, glued against the side of a chimney or other wall, in which there are deposited from four to six white eggs. The young leave the nest when partly grown and cling to the wall like the parents. In fall migration swifts gather at nightfall in great flocks that wheel in funnel-shaped clouds over chimneys, into which they descend to roost. For many years their winter home was unknown, and when they disappeared in fall the ignorant believed that they had gone into hibernation for the winter. Recently, however, they have been recorded as migrants in Haiti, Mexico, and Cen tral America, and it is assumed that they pass the winter somewhere in northern South America. The chimney swift is found in summer from southern Canada to the Gulf coast, ranging from the Atlantic seaboard west to eastern Texas, Montana, and central Alberta. WHITE-THROATED SWIFT (Aero nautes saxatilis saxatilis) In a family remarkable for power of flight, the white-throated swift is preeminent among the species found in the United States. I recall dis tinctly my amazement at its seemingly incredible speed, on my first sight of these birds wheeling over the great abyss of the Grand Canyon. With out seeming effort, they swung back and forth over courses a mile or two in length, with a power and ease that on many subsequent encoun ters have remained interesting and attractive. This swift is most common in mountainous re gions, where it is found principally in the vicinity of the cliffs on which it nests, but ranges at times in level country, particularly during its migra tions. When feeding, it may come near the ground to fly about with ordinary speed, but at other times darts about high overhead, its pres ence advertised by shrill, high-pitched, laughing calls. White-throated swifts breed in crevices and crannies in cliffs, caves, and old ruins, making their nests of soft vegetable materials and feath ers, fastened together by a gluelike substance from the mouth secretions and fastened by this same cement to the rocks against which they are placed. The eggs are pure white and number four to six in a set. From the rapidity of their flight, these birds have few enemies except the owls and small climbing mammals that capture them at night in their roosts in cliffs and caves. The white-throated swift is found in summer from south central British Columbia and southern Alberta to the Black Hills and Lower California. In winter it occurs from central California south ward. VAUX'S SWIFT (Chaetura vauxi) This western species is similar to the chimney swift, from which it differs in slightly smaller size and somewhat paler coloration. It is far less numerous than the chimney swift and in many areas in its range it is found only casually. The flight and general habits of Vaux's swift are also like its eastern cousin, it having similar squeaking calls and like mannerisms in flight. It often feeds high in air for long periods during the day, so that most observations pertaining to it are un satisfactory glimpses of its small form darting erratically through the sky, perhaps in company with swallows, from which the swift is readily distinguished by its more rapid flight. In nesting, Vaux's swift still resorts to the hollow trees of its ancestors, constructing a shal low saucer of twigs or of pine needles fastened together with the salivary secretion and with this glued to the walls of its safe retreat. The eggs are four to six in number and are pure white. While usually it nests in tall, dead stubs, the birds ordinarily select those that are hollow throughout their length, descending inside to near the bot tom. Instances are on record where the nests have been placed actually below the surrounding ground level. Vaux's swift nests from southeastern Alaska, central British Columbia, and Montana south to the Santa Cruz Mountains, California. and Ne vada. It migrates through Arizona and Lower California to winter in Central America.