Violet-green Swallows have an extensive breeding range in western North America, but have been little studied. Violet-green Swallows can nest in lone pairs, but often nest colonially, sometimes near human dwellings if nest boxes or other nest sites are available. Competition with other cavity nesters is common.
Violet-green Swallows exhibit strong fidelity to their nest area, often returning in subsequent years. Small flocks are often formed prior to fall migration, but relatively little is known about their migration. As aerial insectivores, swallows must have appropriate weather conditions for foraging.
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Description of the Violet-green Swallow
The Violet-green Swallow has green upperparts, a green head, white cheeks extending slightly above the eye, white underparts, a purple rump with white sides, a forked tail, and long, blackish-purple wings.
The sexes are similar, but males tend to be brighter in color.
The sexes are similar, though females tend to have duller colors.
Seasonal change in appearance
Juveniles are mostly brownish above.
Violet-green Swallows inhabit mountains, open forests, and coastlines.
Violet-green Swallows eat insects.
Violet-green Swallows forage by capturing insects in flight.
Violet-green Swallows breed across much of the western U.S. They winter primarily in Mexico and Central America. The population appears to be stable.
Violet-green Swallows are little-known compared to other North American Swallows.
Where Violet-green Swallows are habituated to people and are using nest boxes, a lucky observer can toss feathers into the air during nest building season and watch the swallows catch them in midair to bring to their nest.
Calls include sharp chirping, while the song is a series of short notes.
- Tree Swallows have bluish-green upperparts, and have no white above the eyes.
The Violet-green Swallow’s nest is built from grass, sticks, and feathers, and is placed in a natural cavity, old woodpecker hole, or nest box.
Number: Usually lay 4-6 eggs.
Incubation and fledging:
The young hatch at about 13-18 days, and leave the nest in about another 23-24 days, though continuing to associate with the adults for some time.
Bent Life History of the Violet-green Swallow
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 Violet-green Swallow – the common name and sub-species reflect the nomenclature in use at the time the description was written.
TACHYCINETA THALASSINA LEPIDA Mearns
This beautiful swallow is well named; the soft velvety plumage in subtle hues of violet and green on the upper surface, the conspicuous white patches on the sides of the rump, and the pure white lower surface combine to make a charming whole, a dainty feathered gem. It enjoys a wide distribution west of the Great Plains and from Alaska to Mexico, and in some places it is one of the most abundant species. A. E. Shirling (1935) writes: “The violet-green Swallow * * * is to the Colorado mountains what the English Sparrow is to eastern and central states. It is the most common bird about cottages and towns. In respect to relative abundance, it exceeds the English Sparrow for the sparrow’s range is confined to human surroundings of houses, barns, and picnic grounds. The violet-green Swallow, while most abundant in the neighborhood of human dwellings, ranges widely up the mountain slopes and unfrequented forest lands.”
Near the coast in southern Alaska, as far north as Ketchikan, in British Columbia and in the vicinity of Seattle, Wash., we recorded the violet-green swallow almost daily, where it seemed to be a common summer bird at low altitudes; here it frequented the towns and villages, much as our tree swallow does in the East, apparently trustful of human society and ready to accept such nesting accommodations as human structures offered. It was also seen commonly in clearings in the woods where there were dead trees for nesting sites, especially in the vicinity of lakes and streams. In California, also, its haunts and habits are similar, strongly reminding us of our familiar tree swallow, which it largely replaces in the West, though sometimes associated with it.
In the mountain ranges of Arizona we found it at the higher elevations, nesting mainly above 7,500 feet and among the pines near the summits; however, a few pairs could generally be found at lower levels in the wooded canyons. In New Mexico Mrs. Bailey (1928) found it breeding in the mountains at elevations varying from 11,300 to 6,500 feet. James B. Dixon tells me that it is a bird of the higher elevations in California; he found it nesting near Mono Lake at 6,500 feet and at Escondido at 1,400 feet. Evidently it prefers to nest in the mountains throughout the southern portion of its range.
Spring: The violet-green swallow is an early migrant and has a long journey before it to reach its northermnost summer resort. Theed Pearse writes to me that he has seen it passing through British Columbia in great numbers in spring, during the last few days in March and through April.
Mr. Rathbun says, in his notes from Seattle: “The first arrivals in spring will generally be seen hawking about over some low meadow. Then, for a short period following, they are likely to be observed flying about the localities where they have been in the habit of nesting in previous years. Then they disappear, not to be seen again during the day. As the season progresses, the birds begin to linger longer about these particular spots, and, when early April comes, the swallows become fairly established in localities where it is their intention to breed. Their twittering notes are a most welcome sound in the spring.”
He tells me that in 1936 bad weather, low temperature, and several inches of snow on March 27 caused the death of many of these swallows. One of his friends found 20 or 30 dead violet-green swallows within the space of a week along a short stretch of highway, and he had reports of others that had succumbed.
Couttship: Mr. Rathbun (MS.) records in his notes his experience with early-morning flight songs, heard long before sunrise, of the violet-green swallow, which appear to be a part of the nuptial performance. I quote direetly from his notes as follows: “June 5, 1923. This morning I arose at 1.45 to make some notes. It is mild, the stars shine brilliantly, and at this hour there is no moon. 2.26 A. IL The first notes are heard coming from a violet-green swallow. Within the next two minutes, notes from a number of the swallows were heard, the birds flying rapidly around. At this time, faint traces of the dawn show in the sky at the northeast, but the stars are very bright as it is clear. At 2.33 A. M., the violet-greens are heard on every side, their notes increasing within the next five minutes, the birds seeming to be at quite a low height. As the morning light slowly grows, the calls of the swallows are even stronger; interjected at times were some musical notes heard only occasionally at the time of the nuptial period. 3.08 A. M. The notes given by the swallows are now becoming less. At this time, the stars are faint. 3.11 A. K. The swallows have ceased calling, having flown about for 45 minutes.”
In recording a similar experience on June 3, 1929, he writes: “The twittering notes, given by the birds in the very early morning hours, are somewhat like their ordinary ones, but there is this difference: the notes are of a shrill, chattering character, more rapidly given, and almost continuous, as if the bird was excited, though sometimes there are very short pauses between the notes. The flight of the swallow is also very erratic, more of a dashing or twisting kind, and each bird seams to somewhat confine itself to a limited territory in the vicinity of where it is nesting. From a long observation of the violet-green swallow in the dim morning hours before sunrise, I incline to the opinion that those in flight are the male birds, and their unusual actions at this time can be attributed to the procreative impulse which is at its height at this time, for the actions are at an end in the latter part of June, when young swallows are in the nest.”
Nesting: The violet-green swallow nests in holes, cavities, and crevices in a variety of situations. In suitable localities, where the birds are often very abundant, the demand is sometimes greater than the supply, competition for the available cavities is keen, and the birds cannot be too particular in the choice of a nesting site. Where nesting cavities are numerous, the swallows often form colonies, with many nests in a suitable tree or cliff. Charles F. Morrison (1888), in Colorado, has “seen as many as twenty pair in a single dead pine, and four or five pair in one limb which had been used first byï the woodpeckers.”
Throughout much of its range this swallow still continues to nest in localities more or less remote from human habitations and under primitive conditions, such as in deserted woodpecker holes and natural cavities in trees, or cracks, crevices, or holes in various kinds of rocky cliffs. Dawson and Bowles (1909) say that, in eastern Washington, they still nest “to a large extent upon the granite or lava cliffs. In the last-named situations they utilize the rocky clefts and inaccessible crannies, and are especially fond of the smaller vapor holes which characterize the basaltic formations. Favorable circumstances may attract a considerable colony, to the number of a hundred pairs or more.”
In Arizona they nest mainly high up on the mountains in old woodpecker holes in the pine belt, but a few pairs nest in the limestone cliffs that form the walls of the upper canyons. In other places they have been reported as using the old nests of cliff swallows and even the burrows of bank swallows. An unusual nesting hole was discovered by Edward R. Warren in Colorado; he says in his notes: “It was in a dead cottonwood about 5 feet above ground, in what appeared to be an abandoned flicker hole. The entrance was rather curiously situated. The bark had been split at the above height and thence down to the ground, the split widening to a foot or more. The bark had kept on growing and the edges were rolled in. The entrance to the nest was under the roll, and was not visible until one stooped down and looked up.”
In the Yukon Valley, Alaska, Dr. Louis B. Bishop (1900b) “frequently saw colonies of from six to ten birds of this species, and one near White River that must have contained over fifty. They were nesting about the cliffs as a rule, but several times we saw them enter holes in banks similar to those of Cli’vicol#i ripai*t, while at Fort Selkirk they were nesting in the interstices between the logs of the cabins.”
In the vicinity of Seattle and Tacoma, Wash., the violet-green swallow, according to Thomas D. Burleigh (1930), “has readily accepted the benefits to be derived from the proximity of man, for during the breeding season they were rarely seen far from houses. * * * A nest found June 9 held four slightly incubated eggs, and was on a beam in a corner inside the attic of an old unused house. It was a large mass of weed stems, grasses and feathers, the middle being neatly cupped and well lined with large chicken feathers. Another nest found June 13 held six half incubated eggs, and was in a cavity between two logs in the side of an old log cabin.”
S. F. Rathbun writes to me from Seattle: “For 16 consecutive years a pair of these swallows nested in a box placed under the eaves of our house in the city.” Some time was usually consumed in the selection of nesting sites among the four boxes that he had set up, as much rivalry took place between these swallows, a pair of tree swallows and a pair of English sparrows. The sparrows were allowed to occupy the least desirable box, and he kept them busy all summer by removing the eggs at intervals. He says that the violetgreen swallows construct their nest in a very leisurely manner, sometimes requiring as much as three weeks to complete it, and then a day or two may elapse before the first egg is laid. “The nesting material consists of an abundance of straws and dry, dead grasses often with bits of string, and is warmly lined with an abundance of feathers, at times a few horsehairs being woven into the lining.”
In the Kootenay Valley, British Columbia, Joseph Mailliard (1932) found this swallow “commonly nesting, in the height of the flood, in the dead trees and stumps of the river bottom in company with the preceding species [tree swallow]. A number of pairs of the Northern Violet-green Swallow were found in possession of a lumber yard in town and were nesting inside large, square piles of board lumber that was loosely cross-laid so as to leave space for circulation of air for drying purposes.”
Eggs: The violet-green swallow generally lays four or five eggs to a set, but sets of six are not very rare, and as many as seven have been recorded. The eggs are usually ovate and pure dead white, without markings. The measurements of 50 eggs average 18.7 by 13.1 millimeters; the eggs showing the four extremes measure 20.8 by 12.7, 17.3 by 13.7, 16.3 by 12.7, and 17.3 by 12.2 millimeters.
Young: Mr. Rathbun tells me that the incubation period is 13 or 14 days, and that the young are on the wing within 23 days; they remain near the nest for a few days and then disappear from the locality, to be seen only occasionally thereafter. During the first few days after they leave the nest they make only short flights, but as the birds become stronger these aerial excursions become more extended. When at rest on some favorite perch, such as a telephone wire, the young are constantly calling to their parents and are fed by them from time to time. Frequently one launches itself into the air to meet its parent and take its food while on the wing, a graceful performance.
Leon Kelso (1989) made some observations in Colorado on the feeding of young violet-green swallows. “The female secured most of the food for the young; the male brought something only occasionally. When returning with food they would sweep about the nest in wide arcs, then, coming to a point about 50 ft. or more in front of it, would fly directly to and in the entrance.” IHe noted that food was brought at frequent but widely varying intervals; during the first afternoon the “visits cam~ at 1 to 30 second intervals.” On another day, August 1, the intervals varied from 20 seconds to four minutes, considerably over a minute intervening in most cases. Periods spent in the nest between feedings varied from one second to over two minutes.
Mr. Shirling (1935) noted on two occasions that more than one female attended a brood of young, entered the nest and apparently fed them:
One male bird stood guard and rarely entered the nest. He was kept busy chasing other male swallows away, but did not seem to object to either of the females coming. [At another nest] there was more than one female swallow interested in the nest. At one time three female birds and one male were at the nest. The male, keeping guard, paid little attention to the other birds unless it was a bird of some other species that arrived, or a male Violetgreen Swallow. * * * Female No. 1 seemed to have priority of claim to the nest. She often remained with her head at the doorway and pecked at Intruders. She was also on very good terms with the male. The other female birds seemed to he merely meddlesome busybodies who had no home of their own nor young to care for, and, like a cat that has lost her kittens, just had to have some one to mother.
Apparently only one brood is reared in a season; Dawson (1923) says so, and I can find no evidence of a second brood. Probably a second attempt would be made if the first attempt failed. Harry S. Swarth (1904) says that in the Huachuca Mountains, where these swallows breed at the higher elevations, “toward the end of July, 1902, after the young were out of the nest, they moved down into the lower parts of the mountains, where young and old were seen together in large flocks; the young birds being, in many cases, still fed by their parents.”
Plumages: I have seen no- unfledged young, which are probably like those of the closely related tree swallow. Ridgway (1904) describes the young bird in juvenal plumage ~as “above plain sooty grayish brown, darker on back, where faintly glossed with purple, violet, or bronze; a white patch on each side of rump, as in adults; lores dusky gray; auricular region and postocular spot mottled sooty brown and grayish white, or uniformly of the former color; under parts grayish white anteriorly, pure white posteriorly, the chest usually tinged with sooty brown, especially laterally, where sometimes with a distinct narrow transverse patch of brown.”
This plumage is worn through the summer and perhaps early fall; apparently a complete postjuvenal molt occurs in. September and October, producing a first winter plumage, which is practically the same as the winter plumage of the adult. Both adults and young birds, in fresh fall plumage, have the tertials conspicuously margined and tipped with white; these white edgings disappear by wear during the winter. Adults have one complete annual molt in late summer and in the fall. Wear produces only a slight effect on the spring plumage. Females, after the postjuvenal molt, are always much duller in color than the males, with gray mottling on the sides of the head, making them readily distinguishable.
Food: The violet-green swallow seems to live entirely on insect food, taken on the wing. It does not differ materially from other swallows in this respect. Prof. F. E. L. Beal (1907) examined 67 stomachs and found that bugs (Hemiptera), mostly leafhoppers and leafbugs, constituted 36 percent of the food. Diptera (flies) came next, 29 percent. Hymenoptera amounted to 23 percent and in July were mostly made up of ants; six stomachs taken on one day were entirely ifiled with ants, and another, taken the next day, was half full of them; the ants were evidently swarming on the wing at that time and were easily caught, as very few were taken at other times. The remainder of the Hymenoptera eaten were wasps and wild bees. Beetles made up over 11 percent of the food, 3 percent of which were useful species and 8 percent harmful beetles. “Three stomachs, collected at the same time in Carmel Valley, are of interest. They contained respectively 42, 45, and 40 percent of scolytid or engraver-beetles. This was in the region of the Monterey pine (Pinus radiata), and there is no doubt that these insects prey upon those trees, and probably were taken when migrating in a swarm to fresh foraging grounds. A few moths, with some unidentified insects, make up the remainder of the animal food, a little more than 1 percent.”
Behavior: AlI swallows are swift and graceful in flight, but the violet-green combines these attractive qualities with exquisite beauty of form and color and with fearless confidence in human friendliness. It is a pleasure to watch these dainty birds, as they sweep by in loose flocks or smaller groups low over the herbage in the open fields, over the surface of some small pond, or up and down the bed of some canyon stream, winnowing the air for insect prey. It is delightful to have one show its confidence in human nature by gliding by us almost within arm’s reach, showing alternately its snow-white breast and the metallic colors of its back, with an occasional flash of golden sheen. But they do not always course low over the ground or water; on clear, warm days, when the insects are flying high, they are often seen circling at a great height, when they seem to be just white-breasted swallows. They are often seen perched in long rows on the telegraph wires, like other swallows, or sunning themselves in the tops of leafless trees. They have endeared themselves to many bird lovers by the almost friendly way they have accepted the artificial homes erected for them in our towns and cities, returning each spring to greet their human friends.
Voice: The early-morning flight notes are referred to under courtship. Ralph Hoffmaiin (1927) mentions these as follows: “Before dawn when the Robin chorus is in full swing, Violet-green Swallows fly about in the darkness repeating over and over two or three slight notes, tsip tseet t8ip. Their ordinary notes are a rapid twitter.”
Field marks: The violet-green swallow might easily be mistaken for a tree swallow at a distance, though its wing strokes are more rapid and it sails less; it appears to me somewhat chunkier in form, though it is actually very little shorter. ‘When reasonably near, the white patches on the sides of the rump are very conspicuous from either above or below. At short range, the white of the throat may be seen to extend well up on the sides of the neck and over the eyes, whereas in the tree swallow the eyes are entirely surrounded in the black of the crown. The colors of the back may be distinguished only in good light.
Enemies: The English sparrow is one of the worst enemies of this and other swallows, as it preempts the nesting boxes or attempts to oust the swallows from them. The sparrows begin nesting operations earlier than the swallows and thus have the advantage, but, when once well established, the swallows are not easily driven out. Bird lovers that want to have swallows in their bird boxes must keep the sparrows under control.
Violet-green swallows are sensitive to weather conditions; migrants in early spring are often confronted by a sudden cold spell, which forces them to retreat. At such times, when insects are scarce or driven to cover, it is impossible for the swallows to obtain sufficient nourishment and many of them perish and are picked up in an emaciated condition.
Mr. Rathbun tells me of one that was building a nest in one of his boxes, using some-horsehair in the lining; its wing became entangled in one of the hairs, and it might have perished if it had not been released by Mrs. Rathbun.
Fall: Mr. Rathbun (MS.) says: “After the young are on the wing these birds disappear from the localities where they have nested unless such happen to be in the vicinity of water, for the species seems to be partial to such surroundings in the vicinity of streams or lakes or even along tidewater. Here the birds will be seen hawking above the low-lying fields or along the littoral line and, on occasions, perched in numbers on the telegraph wires in the vicinity. These localities appear to be the resorts of the violet-greens up to the time when they take their departure in the autumn.”
Theed Pearse tells me that this is the first of the swallows to leave the vicinity of Vancouver Island in summer, very few being left by the end of July. Farther south they gather in large flocks during August and depart from Colorado and New Mexico early in September.
Dr. Joseph Grinnell (1908) writes: “Many adults and full-grown young were found congregated about the shore of Bear lake [San Bernardino Mountains, Calif.] July 80 to August 2, 1905. On the bare branches of one dead pine on the north shore of the lake, July 81, hundreds (without exaggeration) of violet-green swallows were perching, mostly young-of-the-year. Individuals were constantly coming and going, and occasionally nearly the entire flock would launch out with loud twitterings, only to gather again within a few minutes. It made me dizzy to watch the restless throng. A similar gathering, though on a smaller scale, was witnessed near the South Fork of the Santa Ana, July 24, 1906.”
Winter: A few violet-green swallows spend the winter in the relatively warm Imperial Valley in southern California, in the lower Colorado Valley, and in northern Lower California. But the main winter range is in Mexico and Central America, as far south as Guatemala and Costa Rica. Dickey and van Rossem (1938) refer to its status in El Salvador as an “abundant, though extremely local, midwinter visitant to the seacoast and mountains.” They say further:
The abundance of this species at tidewater and In the interior mountains, with a vertical gap of some 6,000 feet in distribution, cannot be explained at the present writing. In the winter of 1925: 1926, violet-green swallows were to be seen In large numbers over the tidal flats at Puerto del Triunfo, where they fed from about an hour before sundown to dusk, in company with the even more comnion rough-wings. During the day they spread out over the coastal plain a short distance inland where their actual numbers were not so apparent. This was the only locality In which the species was detected until, in 1927, it was found to be extremely common above 6,000 feet on Los Esesmiles. Here, flocks were seen daily from February 1 to March 10. On warm days they were usually circling back and forth over the cloud forest at 8,000 to 9,000 feet, but when, as was usual, that hunting ground was blanketed in wind-driven fog and clouds, they worked over the pines at 6,000 to 7,000 feet on the sunny, southern slope of the mountain. All of the specimens taken are typical Zepida.
Range: Western North America, and Mexico.
Breeding range: The breeding range of the violet-green swallow extends north to Alaska (Iliamna Lake, Lake Clark, Fairbanks, and Circle); Yukon (Dawson, Fort Selkirk, and Fifty-mile River); and central Alberta (probably Henry House and Red Deer). East to Alberta (Red Deer and Camnore); central Montana (Great Falls, Little Belt Mountains, and Billings) ; western South Dakota (Spearfish, Elk Mountain, and Indian Creek); northwestern Nebraska (Squaw Canyon); central Colorado (Fort Collins, Boulder, Littleton, and Beulah); central New Mexico (Taos Mountain, Glorieta, and San Mateo Mountains); western Chihuahua (Pinos Altos) ; Veracruz (Orizaba); and Oaxaca (Mitla). South to Oaxaca (Mitla); State of Mexico (Valley of Mexico); and southern Baja California (Cape San Lucas). The western limits of the range extend northward along the Pacific coast from southern Baja California (Cape San Lucas, San Bernardo Mountain, and La Paz); to Alaska (Thomas Bay, Cordova, and Iliamna Lake).
Winter range: While the species has been recorded at this season north to central California (Point Reyes, Point Lobos, and Hayward), the normal northern winter limits appear to be southern California (Salton Sea) on the west and northern Veracruz (mouth of the Tuxpan River) on the east. The winter range extends south to western Guatemala (San Geronimo and Chichicostenango) and El Salvador (Los Esesmiles and Puerto del Triunfo). This species has been recovered twice from Costa Rica (Matina River and Bebedero), but this country seems to be south of the regular winter range.
The range as outlined is for the entire species, which has been separated into three subspecies. The typical race, known as the Mexican violet-green swallow (Tachyci’neta thalassina th~~~~),is confined to the Mexican tableland; the northern violet-green swallow (7′. t. lepida) occupies all the balance of the range except the Cape district of Baja California, which is occupied by the San Lucas swallow (7’. t. brachyptera).
Spring migration: Early dates of spring arrival are: New Mexico: Silver City, April 17. Colorado: Boulder, April 22. Wyoming : Yellowstone Park, May 11. Montana: Anaconda, May 6. Alberta : lied Deer, May 7. Arizona: Tombstone, February 18. California: Los Angeles, February 19. Oregon: Portland, March 7. Washington: Tacoma, March 9. British Coluinbia: Okanagan Landing, March 6. Alaska: Fairbanks, May 8.
Fall migration: L ate dates of fall departure are: Alaska: Thomas Bay, August 22. British Columbia: Okanagan Landing, October 15. Washington: Seattle, October 19. Oregon: Portland, October 7. California: Kernville, October 28. Montana: St. Marys Lake, August 10. Wyoming: Yellowstone Park, August 18. ColoradoBoulder, September 9. New Mexico: Chloride, September 23. Arizona: San Francisco Mountain, September 28.
Casual records: A specimen was taken at South Kenwood in the Calumet region, near Chicago, Ill., on May 4, 1897. In Alaska, two specimens were obtained on St. Paul Island on August 22, 1914, and one in immature plumage was taken at Point Barrow on August 26, 1929.
Egg dates: California: 31 records, May 1 to July 1; 15 records, May 25 to June 11, indicating the height of the season.
Baja California: 3 records, May 1 to June 16. Oregon: 19 records, May 27 to July 5; 9 records, June 4 to 17.
SAN LUCAS SWALLOW
TACHYCINETA THALASSINA BRACHYPTERA Brewster
The violet-green swallow of the southern half of Lower California was named and described by William Brewster (1902) as follows:
Similar to T. Zepida Mearns, but with the wing decidedly and apparently constantly shorter. * * * The violet-green Swallow of the Cape Region furnishes an interesting illustration of the recognized fact that isolated, nonmigratory birds are given to having shorter wings than those which regularly perform extended journeys, for in respect to the length of the wing it Is almost if not quite as much smaller than the form which breeds In the regions further to the northward (I. e. California, Oregon, Washington, and British Columbia) as the latter is smaller than true tlw2assina of the Mexican tableland still further to the southward.
This is the characteristic Swallow of the Cape Region, If not the only representative of the Hirundinidae, excepting the Western Martin, which breeds there regularly and plentifully. About La Paz and other places on or near the coast It perhaps occurs only in winter, as Mr. Belding indicates, hut Mr. Frazar found it common on the Sierra de La Laguna in May and early June, and at Triunfo and San Josd del Rancho in late June and July. On the summit of La Laguna it was nesting late In May, and one was seen flying over the highest peak of this mountain on December 2.
J. S. Rowley writes to me: “Comondi was the only place we encountered these little swallows at all abundantly, and here they were rather common because of the creek running nearby and the only surface water for miles.” He found several nests here on May 1, 1933, “containing eggs in various stages of incubation. Sets of two and three seemed more common, but one set of five was taken. All the nests found were made of feathers and hair, and placed well up in old woodpecker holes in the cardons [saguaros] .”
There is an interesting nest, with two eggs, of the San Lucas swallow in the Thayer collection in Cambridge, taken by W. W. Brown, Jr., at La Paz on May 31, 1908. It is reported to have been placed “in a depression on the face of a cliff among the rocks.” It must have been in a rather large cavity that sloped downward at the outer edge, for the base of the nest measures over 5 inches in diameter at its widest part, while at the inner end of the cavity the nest proper is only 2 inches high. The bulky base of the nest is made of coarse weed stems and long, fine grasses, circularly and firmly woven to hold the nest cup in place; the nest cup is neatly and compactly woven of the finest grasses and fibers, and is lined with black and white hair; there are no feathers anywhere in its composition. The inner cup measures about 2 inches in diameter and about 1 inch in depth. It is not only the most peculiar swallow’s nest that I have ever seen, but decidedly the neatest.
The eggs are ovate, pure white, and have hardly any gloss. The measurements of 9 eggs average 17.3 by 12.9 millimeters; the eggs showing the four extremes measure 18.3 by 13.0, 16.8 by 13.5, 16.8 by 13.0, and 17.0 by 12.0 millimeters.