A widespread and social summer resident in much of the western U.S., the White-throated Swift can nest in lone pairs or in colonies. Crevices in cliffs provide nest sites that are quite safe from predators. Large nighttime roosts of White-throated Swifts form in the winter.
Because of its often inaccessible nest sites, much remains unknown about the White-throated Swift’s nesting behavior. The nests that have been found and studied suggest that pairs sometimes reuse the same nest in more than one year. Mortality in adult swifts appears to be low, so they probably live a relatively long time.
Photographs © Glenn Bartley and Greg Lavaty
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Description of the White-throated Swift
The White-throated Swift is dark gray above with white-tipped secondaries, while from below it shows black flanks and wing linings, dark gray wings, and a white throat, breast, and belly. It has a white patch on either side of the rump. Its wings and tail are long and narrow.
The sexes are similar.
Seasonal change in appearance
Juveniles resemble adults.
White-throated Swifts inhabit canyons, mountains and coastal cliffs.
White-throated Swifts eat insects.
White-throated Swifts forage by pursuing insects in flight, capturing prey in midair with their open mouths.
White-throated Swifts breed across much of the western U.S., wherever cliff crevices are available. They winter from the southwestern U.S. southward. The population appears to be stable.
The name Aeronautes means “sky-sailor”, a reference to the remarkable flying ability of this species.
Like other swifts, White-throated Swifts have an expandable throat pouch in which they carry food back to their nest
The call consists of a series of descending notes and twitters.
- Other common North American swifts lack the bold white underparts and rump patches.
The White-throated Swift’s nest consists of weeds, grass, and feathers cemented to the wall of a rocky crevice using the birds’ saliva.
Number: Usually lay 4-5 eggs.
Incubation and fledging:
The young hatch at about 24 days, and begin to fly in about another 6 weeks, though continuing to associate with the adults for some time.
Bent Life History of the White-throated Swift
Published by the Smithsonian Institution between the 1920s and the 1950s, the Bent life history series of monographs provide an often colorful description of the birds of North America. Arthur Cleveland Bent was the lead author for the series. The Bent series is a great resource and often includes quotes from early American Ornithologists, including Audubon, Townsend, Wilson, Sutton and many others.
Bent Life History for the White-throated Swift – the common name and sub-species reflect the nomenclature in use at the time the description was written.
AERONAUTES SAXATALIS SAXATALIS (Woodhouse)
In the mountainous regions of the far west, especially where precipitous, rocky cliffs tower above deep canyons, one may catch a glimpse of these little winged meteors darting about far overhead. It was in the Huachuca Mountains in Arizona where I first saw this marvelous swift; a mountain brook flows swiftly over its rocky bed through a steep and narrow canyon, known as “the box,” so narrow that in some places one can almost touch both sides of it at once; on each side the rocky cliffs rise to a height of 100 or 200 feet, almost shutting out the light of day; and far above us we could see these swifts darting in and out of crevices in the rocks, or cleaving the sky in their rapid gyrations. Swifts are well named, for, in proportion to their size, they are the swiftest birds that fly, and this species is one of the swiftest of them all. I am tempted to quote the following appreciation from the writings of Dr. George M. Sutton (1935) : “The White-throated Swift belongs to the heavens, not to earth. Beautiful as the creature is, when seen lying among the rocks where it has fallen, or on your hand, it somehow is no longer a White-throated Swift at all. Like a fish from the deep sea that has burst in shallow water, it is only a mass of flesh already starting to decay: of feathers that so recently had pushed aside the thin atmosphere of dizzy heights; feathers that twanged and rustled as the bird shot forward a hundred yards in a twinkling; feathers that knew nothing of the shadows of forests, that knew only the shadows of clouds, the full blaze of the sun, the coolness of clean unscaled pinnacles.”
Courtship: Courtship seems to be performed largely, if not wholly, on the wing. W. L. Dawson (1923) writes: “That most friendly of encounters, the nuptial embrace, appears to take place, also, in the air. In this the birds come together from opposite directions, engage with the axes of their bodies held at a decided angle laterally, and begin to tumble slowly downward, turning over and over the while for several seconds, or until earth impends, whereupon they separate without further ado.”
Enid Michael (1926) says: “White-throated Swifts we have seen cling together and pin-wheel down through the air for a distance of five hundred feet.”
Several others have noted a similar performance; and Frederick C. Lincoln has twice collected, with a single shot, two birds in the act, which in both cases proved to be a male and a female (Bradbury, 1918).
But coition may take place in the nesting crevices also, for James B. Dixon says in his notes: “The males are so amative that when we would take the females out of the cracks they would pounce onto them while in our hands; and we actually caught a pair in this way while hanging onto a ladder in front of the nest crack.”
Nesting: The white-throated swift nests in cracks and crevices in almost or quite inaccessible rocky cliffs on the sea coasts on rocky islands off the coast, and in the mountains up to elevations of 10,000 to 13,000 feet. Much has been written about the difficulties encountered in reaching the nests of these birds, for the nesting cliffs are difficult, or impossible, to scale, and when the nesting crevice is reached the nest is placed so far back in a narrow crack that it is often beyond reach and sometimes even out of sight. Some few nests have been found in niches at a comparatively low height in a cliff, but usually a climb on a rope for 75 or 100 feet from the top or the base of a cliff is necessary to reach the nests. This swift is evidently one of the most successful of birds in placing its nest beyond the reach of predatory animals and birds, not excepting the human egg collector.
James B. Dixon has sent me the following notes: “This bird is a common breeder in the rougher, more mountainous sections of the whole of southern California, as I have found them nesting in every county south of Tehacipi, and from the ocean cliffs to the highest peaks up to 6,500 feet above sea level. I have seen them nesting in the dug-out holes of rough-winged swallows and right in the middle of a large colony of swallows, where it was extremely difficult to tell which one of a myriad of holes the swifts were inhabiting.
“Usually the nests are very flimsily built of feathers glued together into one complete structure. The nest naturally takes the shape of the crack in which it is located and therefore takes all kinds of shapes; but where they have room they will build a nice, round, well-cupped nest that is so well stuck together that ii can be dropped from the cliff and not a feather will be lost. Nest building begins very early in spring and continues for a long time. I have seen birds enter the cracks in a cliff early in March with feathers in their bills, which they must have carried for miles, as the feathers were chicken feathers and there were no poultry yards nearer than 6 or 8 miles in an air line.
“In 1915 I made a special effort to collect several sets of eggs. As we did not know when the eggs would be laid and had seen them building their nests so early, we started operations in April. At this time we found the females sitting on their nests and still building by adding occasional feathers. We inspected these locations week by week from early in April until the last of May before any eggs were laid. The females were in the nests the better part of the time, and the minute a female left a nest every male within sight would take after her.
“The main colony of about 12 pairs was located in the center of a 400-foot hard granite cliff. Here we located three nests that could be reached; the others were too far back to be seen, although the sitting birds could be heard twittering and giving their typical shrill calls.”
There is a set of four eggs, with the nest, collected by J. B. Dixon and C. T. Schnack, in the Thayer collection in Cambridge, which came from the same nesting site. In the elaborate data that came with it they state that the nest was located on a large granite cliff in a steep, narrow canyon near San Pasqual, San Diego County, Calif. It was taken on May 25, 1913, from a diagonal crack on the face of the cliff, 175 feet from the top and on a projecting point of the cliff. The nest is a compact wad of white plant down, mixed with feathers, all securely glued together, and is lined with white, brown, buff, and black feathers, with a few small, bright-yellow feathers; it measures about 4 inches in longest diameter and is hollowed to a depth of about three-quarters of an inch; the eggs are badly “flyspected,” as seems to be frequently the case in nests of this species.
There is another interesting nest of this species in the collection, perhaps a different subspecies, taken by Gerald B. Thomas in the Coxcorab Mountains of British Honduras on May 27, 1906. It was located in a cave, 50 feet from the ground, in a high cliff; it was glued to the wall of the cave 10 feet from its mouth. The nest resembles that of the chimney swift in shape and size, being almost too small for the five eggs it contained; it is made of weed stems glued together into a firm basket, and is profusely lined with small feathers, dark brown and white, which look as if they might have come from the parent bird.
Wilson C. Hanna has published two interesting accounts (1909 and 1917) of the nesting habits of the white-throated swift in a quarry on Slover Mountain in the San Bernardino Valley, Calif. He describes the difficulties involved in securing the eggs, shows photographs of the nests, and gives a series of measurements of both the nests and the eggs. In his second paper, he says of the nests:
Both the vertical and the horizontal cracks are used as nesting sites, but with the exception of set no. 5, all that I took were from vertical cracks. It is almost impossible to take nests from horizontal fissures without destruction of the eggs and In the exception noted, a rock weighing at least 35 tons was removed. * * * The location of nest no. 6 was rather unusual, being reached by going into a vertical crack about three feet, then up eighteen inches, then to the side about eight inches. * * *
Nests are constructed, for the most part, of chicken feathers and grasses cemented together and to the rocks, probably by saliva. They vary in size to suit the space between the wails of rock and are usually shallow and narrow. * * *
All nests that I have examined have been infested with numerous “hugs.” In the two nests where birds could be seen while incubating, the Insects could be observed crawling on the birds’ heads. The eggs, In every case, were more or less spotted as a result of the insects, depending upon how long they had been in the nest.
William C. Bradbury (1918) made some elaborate preparations and, with the help of three young men, collected several sets of eggs near Hot Sulphur Springs in Grand County, Cob. He writes:
The cliffs where the birds were seen, bordering the Grand River, east of Sulphur Springs, are of a mixed lava formation, with some parts of hard, ringing material, and others of cracked, crumbling formation, intermixed with seams and deposits of soft lava ash, through which the river has cut Its way in ages past. The visible base of the cliffs is at the top of a steep slope of debris, extending to the Grand River several hundred feet below. * * *
The first available prospect, located by Niedrach through the presence of excrement about eight feet up, and to which he was able to climb, was in a horizontal crevice about two and one-half inches In width, sloping slightly downward and partly filled, In places, with lava, sand and vegetable matter evidently deposited by the wind. Upon reaching the crevice a Swift darted forth nearly In his face, and he caught sight of its mate retreating back into the crevice, from which it was not seen to emerge. Less than an hour’s work resulted In collecting, from a point about eighteen Inches back, our first nest, containing four fresh eggs.
Florence Merriam Bailey (1907) made the interesting discovery that white-throated swifts were nesting in cracks in the walls of the old mission building at San Juan Capistrano, Calif. She located four nests by seeing the birds enter the cracks; but only one nest was actually seen, of which she says: “The nest behind the end of the stone arch was the only one seen and this: as it was ten feet from the ground: only by climbing and peering up the crack. The crack, as seen in the photograph, was behind the capitol of the pilaster on which one end of the arch rested, the capitol having been jarred away from the wall by an earthquake: doubtless that of 1812. About ten inches up this crack the nest could be seen tightly wedged in between walls less than two inches apart. As well as could be seen without destroying the nest, it was made of bark, feathers, grass, and wool.”
Eggs: The white-throated swift lays three to six eggs, oftenest four and frequently five. The eggs vary from elongate-ovate to cylindrical-ovate, or almost narrowly elliptical. They are dead white to pale creamy white and without gloss. As mentioned above, the eggs are often more or less spotted with the excrement of the insects with which the nests are often badly infested. The measurements of 50 eggs average 21.24 by 13.74 millimeters; the eggs showing the four extremes measure 25 by 15, 19.1 by 12.9, and 21.9 by 12.7 millimeters.
Young: Enid Michael (1926) had a young swift in captivity that she kept alive for ten days.
This captive swift slept much of the time, but during his wakeful hours he was a very active bird; shoving and flopping along on his breast he could move rapidly. He was kept In a wooden box with a screened cover, where there were folded flannels into which he could snuggle away and sleep. When awakened he would set out at once to explore his box. He could crawl up the vertical wall of the box without the least difficulty, and one of his favorite stunts was to race about, back down, on the under side of the cover screen. This screen was ordinary mosquito-proof netting. When the screen cover was removed he would scurry up the wall of the box and topple headlong onto the floor. No sooner bad he hit the floor than he would begin to skid about on his breast, using his feet as propellers. He had a fancy for dark cracks, and If he should find such a place he would surely disappear. Best of all, he loved to crawl up one’s sleeve to snuggle warmly under one’s arm. He had very strong feet and claws like a mammal. When attached to one’s garments be clung tenaciously, and each hooked toe nail had to be pried loose before he could be removed.
Plumages: I have seen no very young white-throated swifts, but birds in the juvenal plumage show the same color pattern as the adults, though the colors are duller and less clearly defined. The long, curved claws are highly developed for climbing.
Food: As the food of this swift is obtained wholly on the wing, it probably feeds on whatever small flying insects it can capture. Mrs. Bailey (1928) lists “winged ants and other hymenoptera, bugs, flies, dung beetles, engraver beetles, clover root weevils, leafhoppers, etc.”
Clarence Cottam contributes the following report on the stomach contents of white-throated swifts: “In 21 stomachs of the white throated swift analyzed in the food-habits laboratory of the Biological Survey, the dominant food items appear to be flies (Diptera), the root maggots (Anthomyiidae) being the most important, with the long-legged flies (Dolichipodidae), the flesh flies (Sarcophagidae), and the March flies (Bibionidae) occurring in lesser numbers. March flies make up 100 percent of the food of a bird from Wyoming but did not occur in any of the remaining 20 stomachs. Flies were present in nearly every stomach and formed from 6 to 100 percent of the total contents.
“Beetles (Coleoptera) were well represented, especially the dung beetles (Aphodius), and entered into the diet of ten of the birds with amounts varying from 2 to 84 percent, although they averaged about 10 percent of the total content. Other Coleoptera identified were weevils (Curculionidae),blister beetles (Histeridae), leaf beetles (Chrysomelidae), rove beetles (Staphylinidae), skin or larder beetles (Dermestidae), bark beetles (Scolytidae), and the antlike flower beetles (Anthicidae).
“Bees, wasps, and ants (Hymenoptera) entered prominently into the bill of fare of about a fourth of the birds and were present as traces in three-fourths of stomachs examined. Bees were found to represent from 1 percent to as much as 86 percent of the total content, and ants in two cases formed over 90 percent of the food.
“The true bugs were moderately abundant, the most important being stink bugs (Pentatomidae), treehoppers (Membracidae), leafhoppers (Cicadellidae), and squash bugs (Coreidae); of the last named family, 50 specimens in one stomach formed 67 percent of the content.”
Behavior: The one striking characteristic of the white-throated swift is its dashing, exceedingly rapid, and erratic flight. Of the three western swifts, Vaux’s may be swift, and the black swift swifter, but the white-throated is certainly the swiftest of the three. S. F. Rathbun writes to me: “If there is a faster-flying bird than the whitethroated swift, I would like to see it. Always it appears to fly at top speed. At times the velocity of its flight seems beyond belief. The flight of this swift is often more or less direct, but it darts and swoops, and turns so quickly as it flies that the eye is not quick enough to see how the reversal in the direction of its flight takes place. You watch one as it passes, almost disappears, and in an instant it returns and flashes by. Its flight is so unpredictable that one never knows what next it will do. At rare times, we have seen the white-throated and the black swift in company, and this gave us an opportunity to compare the flight actions of the two. Always the flight of the former is dashing, whereas that of the latter is easy and graceful, as it glides around.”
Mr. Hanna (1917) writes:
It is claimed by some that these birds do not use their wings in unison, but I am of the opinion that they do flap both wings at the same time, at least part of the time if not always. When flying about feeding upon insects, usually at several hundred feet elevation above the ground, they make a few rapid beats with the wings, then soar a little while, then beat their wings rapidly for a few moments and so on. They vary their flight by sharp darts in other directions, probably to catch insects. When returning to the cliffs they often keep their wings beating fairly steadily. Both when penetrating and leaving the crevices they seem to use both their wings and feet as aids to locomotion. * * *
During the heavy rains of January, 1916, quite a number of swifts were found on the ground in a helpless condition. It seems that some of the crevices had become flooded with water which had drenched the birds, causing them to attempt to escape, but it was impossible for them to fly with wet feathers. Several of these birds were kept in a warm place till their feathers were dry enough for them to fly away.
The white-throated swift has well been called the rock swift, for it lives its life in the rocky cliffs and in the air. So far as I know, no one has ever seen one alight on the ground, on a tree, or on any kind of perch. Its feet are not well formed for walking or perching, but they are well adapted, with long, strong claws, for climbing about in the caves and crevices in the cliffs. Mr. Dixon says in his notes: “Their legs are so malformed from nonuse as to be almost nothing but claws, to propel them through the cracks; and they can climb around much the same as bats or mice in such a location.”
The photograph and the diagram published by Enid Michael (1926) illustrate this character.
Dr. Gayle Pickwell (1937) gives an interesting account of the roosting habits of this swift in Santa Clara County, Calif.:
The niche in which the swifts quartered themselves in 1931, and throughout the observations here reported upon, consists of a recess of unknown depth extending beneath a rock face that lies at an angle a little short of the vertical. It is about fifteen feet immediately above Sycamore Canyon Road. The crevice through which the swifts enter and leave measures, it is estimated, from two to three inches in width and about two and one-half feet in length. All the swifts noted, during the dates specified, used this aperture and this one only.
On August 3. the swifts were flying about in the canyon when first observed just at sunset. A crude estimate made of their numbers in the air gave from one hundred to two hundred individuals. Prior to entering the night roost the birds streamed in a procession into the shadows by It and then turned out into the light of the canyon. Shortly thereafter they entered the rock, streaming in with unbelievable rapidity. Three or four struck the crevice simultaneousiy, and now and then they struck one another. Twenty or more entered in an interval of one or two seconds. The entire flock was housed between 7: 20 and 7: 25 p. in., and a constant chattering thenceforth welled from the rock face. The sun had set some time previously, and deep shadows filled the gorge of the canyon.
On September 21, a similar performance was witnessed, but the number had decreased to approximately 49 birds; these all entered the rock in exactly two minutes, between 6: 30 and 6: 32 p. m. On October 24, “the birds went into the roosting niche as fast as shot poured through a funnel; faster than the tongue could waggle in an attempt to count.” They all entered within a space of ten seconds. Later observations were made in November and in January; at the latter time only about a dozen swifts were seen to use the roost.
Voice: Dr. Alexander Wetmore (1920) says: “The call note of this bird is a shrill laughing he he lie he heard usually when two or three are coursing along together.” Ralph Hoffinann (1927) writes: “In spring and during the breeding season while pursuing each other about the cliffs in which they nest they utter a shrill twitter, suggesting the syllables tee-dee~ dee, dee, dee.” Mr. Hanna (1909) describes the vocal powers more fully, as follows: “The swifts do not seem to have any musical ability, but their notes or calls are pleasing, especially to one who is studying them. One series of peculiar shrieks is given while the bird is in rapid flight and is suggestive of joyous freedom. Another series of notes is given when the birds are in the crevices, which sound very much like the twitterings of small chickens as they cuddle under their mother’s wings, only the swifts’ notes are much louder. These twitterings are quite a contrast to the wild shrieks, and they cannot help but suggest comfort and satisfaction.”
Field marks: White-throated swifts are very apt to be associated with violet-green swallows, when insects are flying low and the birds are coursing about at no great height above the ground; at such times it is often confusing to try to pick out the swifts, as they dart about among the swallows. But the shape of the swift is very distinctive, with its long, narrow wings set, as it sails, in the form of a cross; and its wing strokes, as it flies, are much more rapid than those of the swallow. Moreover, the swallow is all white on the under pads, whereas the swift looks mainly black, except for the conspicuous white throat, a central streak of white on the breast, and a white patch on each side of the rump. These white markings will easily distinguish the white-throated from the other two western swifts.
Winter: At least a few white-throated swifts attempt to spend the winter as far north as west-central California, although some of them evidently perish in the attempt, for lack of food or from the effects of the cold. Dr. Gayle Pickwell’s (1937) observers reported that during January 1937 only about a dozen swifts were seen entering the roosting place in the rock in Santa Clara County, referred to above, and that two or three dead birds were found on the ground below the rock.
Mr. Hanna (1917) reports that “during the extremely cold wave of early January, 1913, eight, to me perfectly healthy, swifts were taken out of a crevice where they, with many others, seemed to be roosting in a dazed or numb state. They were kept in a room for about six hours and then turned loose, one at a time, a few hundred feet from the point where they were captured. All flew away in a dazed fashion and nearer the ground than usual and none were observed to return to the place where they were captured. * * * The facts are that these birds are not observed for many days in the coldest weather, yet are found to be plentiful within the rocks, in a dormant state.”
Range: Western North America north to southern British Columbia.
Breeding range: The breeding range of the white-throated swift extends north to southern British Columbia (Vaseux Lake); Montana (Libby, Columbia Falls, Yogo Creek, and Billings); and northwestern South Dakota (Slim Buttes). East to western South Dakota (Slim Buttes, Elk Mount.ains, and Hot Springs); northwestern Nebraska (West Monroe Canyon) ; southeastern Wyoming (Goshen Hole Rim); eastern Colorado (Chimney Canyon, Golden, and Garden of the Gods); New Mexico (Lake Burford, Cafion el Diablo, Anton Chico, and Capitan Mountains); western Texas (Davis Mountains and Chisos Mountains); Tamaulipas (Jaumave); Hidalgo (Chico); and El Salvador (Los Esesmiles). South to El Salvador (Los Esesmiles); western Guatemala (Duenas); southwestern Chihuahua (Jesus Maria); and Baja California (Guadalupe Island). West to Baja California (Guadalupe Island, San Fernando, San Ysidro, and Los Coronados Islands); western California (Escondido, San Juan Capistrano, Santa Cruz Island, Santa Barbara, San Luis Obispo, Pine Canyon, and probably Mount Lassen); central Washington (Lake Chelan); and British Columbia (Fair View and Vaseux Lake).
The range above outlined is for the entire species, but a southern subspecies (A. s. nigrior), apparently resident in the southern part of the range, is now recognized.
Winter range: In winter these swifts are found north to California (Mum Rock Canyon, Santa Clara County, Redlands, Indio, and Salton Sea); casually central Arizona (Big Sandy Creek and Phoenix); and southwestern New Mexico (15 miles southwest of Hachita and Chloride). From these northern limits the winter range extends southward, probably to Guatemala and El Salvador.
Spring migration: Early dates of spring arrival are: New Mexico: Chloride, March 6. Colorado: Colorado Springs, March 20; Durango, April 4; Palisades, April 25. Wyoming: Laramie, April 24, Midwest, April 28. South Dakota: Sioux National Forest, May 12. Montana: Billings, April 23. Arizona: Tucson, March 9; Paradise, March 14; Grand Canyon, March 25. Utah: Salt Lake, May 1. Washington: Everett, May 10.
Fall migration: Late dates of fall departure are: Utah: Willard, September 4. Arizona: Grand Canyon, October 6. South Dakota: Hot Springs, September 9. Wyoming: Laramie, September 9. Colorado-Boulder, October 2.
Casual records: A specimen of this species was captured alive at Hillsdale, Mich., in August 1926; and another was obtained at Hot Springs National Park, Ark., on May 4, 1935.
Egg dates: California: 86 records, May 8 to June 21; 43 records, May 21 to June 3, indicating the height of the season.