[Published in 1942: Smithsonian Institution United States National Museum Bulletin 179: 439-458]
The familiar barn swallow is widely distributed over most of North America, breeding from northwestern Alaska to Mexico and from the Atlantic to the Pacific Coast, including much of Canada and the United States.
Everybody who notices birds at all knows, admires, and loves the graceful, friendly barn swallow. No bird in North America is better known as a welcome companion and a useful friend to the farmer, as it comes each spring to fly in and out of the wide-open barn door, delighting him with its cheerful twittering, or courses about the barnyard in pursuit of the troublesome insects that annoy both man and beast. The peaceful beauty of the rural scene would lose much of its charm without this delightful feature. But such a charming rural scene is not so common as it used to be. The old fashioned barn, with its wide open doors, never closed, its lofty haymow, and the open sheds where the farm wagons stood are being replaced by modern structures, neatly painted buildings, with tightly closed doors and no open windows through which the birds can enter. Horses are replaced to a large extent by automobiles and tractors; cattle are housed in modern dairy barns; and the open haymow is disappearing. There is no room for the swallow in modern farming. Must it return to its primitive style of nesting or will other means of encouraging it to nest in our farmyards be employed? The birds will stay with us if we supply them with supports for their nests; a two by four joist, rough and not planed, nailed to the outside of a building, flat wide side against the wall, and placed well up under the eaves with about 5 inches of clearance, will accomplish the desired results.
Spring.--From its winter range in South America the barn swallow evidently migrates to North America over widely separated routes, though the West Indies and the Bahamas to Florida and through Central America and Mexico to more western points. By the former route the vanguard reaches Florida early in April, but the migration continues well into May and a few are seen even in June. Alexander F. Skutch writes to me: "In Central America, the barn swallow occurs chiefly if not solely as a transient, passing southward in great numbers during September, and again migrating toward the North from mid-March until mid-May, with a maximum of abundance during April. In the more settled parts of the country they are frequently seen resting in long rows on the telegraph wires and power lines, often in company with resident or migratory rough-winged swallows, and sometimes with cliff swallows. They seem to migrate by day, for I have sometimes seen great numbers of them fly overhead in loose flocks in a direct, undeviating course, northward in the spring and south or southeast in the autumn."
The hardy tree swallow often arrives in New England fairly early in March; but the date depends largely on the weather, which is often cold enough to cause a retreat. It comes as a harbinger of spring, but we never forget the old saying that one swallow does not make a summer. But when the more delicate barn swallow appears, a full month or more later, and we see it gracefully skimming low over the fields and ponds or inspecting its former nesting sites, we begin to feel that welcome spring is here, or at least near at hand. Mr. Forbush (1929) writes:
During the latter part of April the pioneers of the Barn Swallow host usually appear in Massachusetts. Sometimes they come too early and are met by cold and storm and so, unable to obtain food, they seek shelter in some building or huddle together behind a closed blind or window sill on the south side of a house until the sky clears and the temperature moderates. By snuggling together in their nest, some of these birds have been able to survive two or three cold days, when morning outdoor temperatures were as low as 15 to 17 degrees above zero mark, but such temperatures may be fatal, even when the birds are well protected.
If, when the Swallows arrive, they find the building closed in which they are accustomed to breed, they sometimes approach the house and fly about it, or about any inmate who appears, twittering and calling until someone takes pity on them and opens a door or window, when they immediately enter, showing their gratification by happy excited twittering. Many farmers cut a small hole in a barn gable to accommodate the birds.
At the northern end of the migration route the arrival is, of course, much later. Dr. E. W. Nelson (1887) says that, in northern Alaska, "this swallow arrives as soon as mild spring weather sets in, generally from the18th to the 23rd of May. The sea is still covered with an unbroken surface of ice as far as the eye can reach, and winter appears to be hardly gone when the first arrivals reach Saint Michaels and come fluttering about their former nesting sites." Lucien M. Turner (1886) places its arrival at a somewhat later date:
The Barn Swallow arrives at Saint Michael's about the 7th of June. A few of the more intrepid ones may arrive some few days earlier. By the 15th of the month as many as forty pairs have been counted in the dusk of twilight, which is light enough to see to read by at midnight during this season of the year. . .
In the spring of 1876 snow squalls and frosty weather held until late in June. The poor birds had no opportunity to recover from their exhausted condition, resulting from their long flight north. Many of them succumbed to the chilling weather, while others, benumbed by the cold, permitted themselves to be handled and seemed to enjoy the warmth given out by the hands, as they nestled closely between them, without evincing any fear.
Courtship.--The actions of mating barn swallows are most pleasing to watch, as much of their love-making is done on the wing. Long, graceful pursuit flights carry the birds in and out of the barns, back and forth through the barnyard, around the buildings where they are accustomed to nest, out over the open fields. Their flight is swift and hurried, accompanied by constant twittering or louder excited outcries, as if each were trying to outdo the other in their expression of springtime ardor. Finally, the female, satisfied that her pursuer is worthy of her, comes to rest on some convenient perch, the roof of the barn or a telephone wire. By way of invitation she twitches her wings and tail and turns her head from side to side, as the male flutters up and alights close beside her. There they rub their heads together, interlock their bills, or preen each other's plumage in happy love-making. Copulation may take place at once, or they may fly off together to choose which of their old nests or nesting sites they will use.
Nesting.--We naturally think of the barn swallow as nesting in barns, and such has seemed to be their preference, where suitable old-fashioned barns can still be found. But when the red men roamed this continent, before the white men invaded it, there were no barns, and the swallows had to build their nests in such natural conditions as would suit their needs, giving them security for their nests and protection from their enemies. They found security and protection in rocky caves, in crevices in rocky cliffs, on shelves of projecting rocks where some protection from above was afforded, and even in holes or natural cavities in cutbanks. Dawson and Bowles (1909) thus describe one such primitive nesting site at the head of Lake Chelan, Wash.:
The shores of the lake near its head are very precipitous, since Castle Mountain rises to a height of over 8,000 feet within a distance of two miles. Along the shore-line in the side of the cliffs, which continue several hundred feet below the water, the waves have hollowed out crannies and caves. In one of these latter, which penetrates the granite wall to a depth of some twenty feet, I found four or five Barn Swallows' nests. . . . Other nests were found in neighboring crannies outside the cave. . . .
Mr. F. S. Merrill, of Spokane, reports the Barn Swallow as nesting along the rocky walls of Hangman's Creek, in just such situations as Cliff Swallows would choose; and back in '89, I found a few associated with Violet-greens along the Natchez Cliffs, in Yakima County.
A colony of some twenty pairs may be found yearly nesting on Destruction Island, in the Pacific Ocean. A few of them still occupy wave-worn crannies in the sand-rock, overlooking upper reaches of the tide, but most of the colony have taken refuge under the broad gables of the keepers' houses.
O. J. Murie has sent me the following quotation from Ernest Ingersoll's "Knocking Round the Rockies," describing the primitive nesting habits of the barn swallow, as he found them at Hot Sulphur Springs, Colo., in 1874:
The niches in the rocks were occupied by large colonies of barn-swallows. . . . Sometimes the niches in the lime-rock (the whole mass of which had been built up of deposits from the mineral waters) were so close together that there would be half a dozen in a square yard; yet every one had its burnt-breast tenants, and the twittering silenced the gurgle and sputter of the rapid stream at the ledge's base. The floor of each niche was hollowed out, so that it only required to be softly carpeted to constitute it a perfect nest. For this grass-stems and a few large feathers were used, precisely as in our eastern barns. But here the birds had greatly economized labor by occupying the niches, for they needed not to build the firm underpinning and stout high walls which become necessary in the barn, or on an exposed rock shelf, to prevent the eggs and young from rolling out; all these happy birds had to do was to furnish a home already made.
Although the above observations were made many years ago, I have no doubt that in many remote or thinly settled localities barn swallows still continue to nest under similar natural conditions. James B. Dixon writes to me that in San Diego County, Calif., as late as 1925, he found them nesting in caves in the ocean wall.
Barn swallows were quick to take advantage of the superior nesting sites offered by various man-made structures; and probably they also felt a sense of added security in their close association with friendly human beings. As civilization advanced, the swallows gradually learned to adopt such suitable nesting sites as they could find in, on, or under various types of buildings, in or on the outside of barns, sheds, or other farm buildings, inside of vacant houses, under the eaves of dwelling houses, under wharves and boat houses, and under bridges and culverts. In the rural districts of old New England, the old-fashioned barn, with its wide-open doors and its lofty haymow, seems to be the commonest and most characteristic nesting place. Here their mud nests may be plastered on the vertical surface of a beam or rafter, if it is not too smooth, but preferably where it can get some support on the flat surface of a beam or shelf, in the angle of a cross brace, or in a corner where two sides will be supported; the iron rail of a hay track, a loop of hanging rope, an iron hook, or wire loop, or even a projecting knot on a rough timber may offer the necessary initial support. We seldom find more than six or eight nests in a barn, but I have known of as many as 27 in a single barn here in eastern Massachusetts; and Dr. Charles W. Townsend (1920b) "counted fifty-five nests of this bird in a large barn at Ipswich, nearly all of which were occupied."
A. Dawes DuBois has sent me some notes on nests under bridges in Illinois. Five of these nests were attached to the vertical face of a floor joist, over water. Another was placed on top of a cross beam at the end of the bridge, fitted into a corner formed by the vertical faces of a joist and another beam at right angles to it. The tops of the nests were about 2 inches below the floor boards of the bridge. A nest under an iron bridge was stuck to the vertical web of an I-beam, but was so placed that the bottom of the nest rested on the lower flange of the beam.
Frank L. Farley tells me that, near Camrose, Alberta, "the barn swallow has apparently departed entirely from its natural nesting situations. Here they have not taken to the barns, but now they are increasing in numbers and nest entirely under bridges and culverts." James B. Dixon says in his notes that in San Diego County, Calif., they nest on the highway bridges that cross the estuaries along the ocean front; and in the San Joaquin Valley he has noted large colonies under bridges and beet-loading platforms.
Dr. Samuel S. Dickey writes to me that while staying at a small frame summer hotel built for the use of fishermen, at Beach Haven, N.J., he noted a number of barn swallows flying about and disappearing under the hotel building. "Since the building was erected on piles, 6 feet over deep water, it left a space about 5 feet high underneath. Here the swallows found ample room for breeding purposes. They were enabled to withdraw on three open sides. When we clambered down among the piles and planks, we caused a shower of birds to evacuate. And there, plastered upon crossed sticks next to the floor, were 15 nests." He visited a colony at Nantasket Beach, near Boston, where they bred under wharves and boat houses overlooking the sea.
In northern Alaska, about St. Michael and Nome, barn swallows are fairly common and seem to appreciate the advantages of nesting on what few buildings they can find; if buildings were more numerous they would probably increase in numbers. As it is they build their nests under the eaves of buildings, on projecting beams, inside empty houses, and even in the deserted sod houses of the Eskimos. The nests are profusely lined with white ptarmigan feathers, which are plentifully scattered over the tundra after the spring molt. In the Aleutian Islands we did not see any barn swallows west of Unalaska.
A few unusual nesting sites are worthy of mention. It is hardly to be wondered at that the swallows would continue to incubate and rear their young in a building that was moved after they had started nesting, but that they should continue to build and occupy their nests repeatedly on moving trains or boats is a remarkable illustration of their persistency and confidence, or of the scarcity of more suitable and stationary situations. At least two instances of nesting on moving trains have been reported. Harry S. Swarth (1935) reports that a narrow-gauge train, which carries passengers and freight over a 2-mile portage from Lake Tagish to Lake Atlin, British Columbia, provides a home for a pair of barn swallows. He says:
About the buildings at the Tagish Lake end of the line innumerable Barn and Cliff Swallows nest. Under the eaves around one of the larger sheds there is an uninterrupted frieze of the Cliff Swallows' mud nests. But the really interesting feature of this colony lies in the action of a pair, or more properly a succession of pairs, of the Barn Swallow (Hirundo erythrogaster), in nesting on a moving train. For many years past one pair of swallows have built their nests and raised their broods on some part of the train that crosses the portage. They were first commented upon by E. M. Anderson, who, in the annual report of the Provincial Museum of Natural History (Victoria) for 1914, describes the nest as he saw it in one of the coaches. I have seen it on each of several years that I have visited the region, and in all probability the nesting is an annual occurrence. The train crew take a personal interest in their guests, and for some years the swallows occupied an open cigar box that was fastened for their use under the roof of the open-sided passenger coach. In 1934 the nest was supported near the center and immediately under the roof of the baggage van, the sides of which are protected only by canvas curtains. I had occasion to cross the portage on the evening of June 21. When we embarked at the eastern end the swallows were not at home, but as soon as we arrived at the Tagish terminus both birds swooped into the car. There they settled down for the night, despite the fact that baggage was being piled beneath them to within a few inches of the roof.
Nesting year after year on a moving boat is another unusual habit, yet Burton W. Gates (1903), who had previously noted it, writes:
I recently wrote Captain Harris, formerly of the steamer Horicon, on Lake George, New York, inquiring if the Swallows which, in the summer of 1900, nested beneath the guard-rails of his steamer had, in the three succeeding years, nested in similar places. His prompt reply was to the effect that "the Swallows have built their nests under the guard-rails of the various steamers which I have been running [I judge upon Lake George] for the past fifty-five years." The Captain is now retired from duty but inquired of his son, the pilot of the new steamer Sagamore, regarding the habits of the birds in the past two seasons. To this, the Captain further wrote: "My son says that the Swallows were still with him this summer." Thus it would seem that the Swallows of Caldwell, New York, have, for generations, had a nesting habit peculiar to that locality.
It is perhaps not strange that the barn swallow should occasionally appropriate an old nest of the phoebe, as these birds often nest under bridges, or that the swallow should sometimes nest in a well or an abandoned mining tunnel, which somewhat resemble caves. Illustrating their confidence in humanity, Mr. Forbush (1929) mentions the following cases: "A pair built their nest close by a blacksmith's forge and reared their young, regardless of wheezing bellows, clanging hammers and showering sparks. Another pair in Falmouth, Massachusetts, built their nest in a room on a large farm, where agricultural products were daily prepared for market. They threaded their way in and out among the busy workers, industrious and fearless in their care for their growing young. A pair in Westborough, Massachusetts, took for their nesting place a narrow shelf, in a barn, five feet above the floor, almost over a cow, where the milker could look directly into the nest. They stayed there and raised their young."
In building their nests the barn swallows show themselves to be expert masons, but unlike the cliff swallows and like the ancient Egyptians they cannot make bricks without straw. The first requisite is some clayey or otherwise sticky mud, which the birds obtain from the shore of some body of water or from mud puddles in roads or fields. Professor Herrick (1935), who has made a careful study of the nesting habits of this swallow, feels confident that the bird's saliva is not a factor in making the mud more adhesive. Authorities differ as to how the mud is carried. Dr. Dickey says that "they waddle about on their short, weak legs and roll pellets of mud, which they place on top of the upper mandible and so bear to the nesting site." Lucien M. Turner (1886) confirms this:
I have watched them for hours at a time, and when my eyes were not to exceed four feet from the birds at work. . . . The neck is stretched out nearly its full length and the head kept with the bill at a right angle to the neck. A slight pressing of the beak into the earth and a tugging twist of the body pulls toward the bird a small pellet of mud. The bird then lowers its neck to the ground with the beak on the opposite side of the pellet (or on the side next to the bird). The beak is now thrust under the pellet until the mass of mud is pushed onto the top of the bill and rests against the forehead. This is the manner in which it obtains the mud and is in position to enable the bird to deposit it. The mud is also smeared with the top of the beak.
Professor Herrick (1935), on the other hand, says:
The mud, which, as we have seen, is always carried in the barn swallow's ample mouth and throat, is pressed out through the partially opened mandibles as a semiliquid mass, at first in small and later in larger globules, a little here and a little there. These globules are eventually laid down in tiers and rows, and their uniformity is due to a uniform method of production and disposition.
This semifluid building mud or clay is made to adhere to a previously moistened surface of the wood by a peculiar 'tapping movement' of the bill. . . . To secure this all-important contact a small area is first thoroughly moistened by repeatedly bringing the bill to it simultaneously with a visible muscular contraction in the throat region which presses out of the mouth drops of a liquid which, from the freedom with which it runs along the grain of the wood, must be mainly, if not wholly, water.
The masonry is started with a mud disk, or plaque, attached to the vertical surface, around and on which the structure is built up; the layers of mud are alternated or mixed with pieces of grass or straw; these are short at first and worked in with the mud, but later, longer pieces are used and the ends left hanging to some extent. "The method of depositing and fixing these little spears was interesting. A bird would come with a delicate blade or stem held crosswise in its bill, and the moment it touched the beam, a small pellet of wet mud would issue from the mouth and, like a drop of sealing-wax, fix it promptly to the vertical surface."
Both sexes work together, industriously and harmoniously, in the construction of the nest. Professor Herrick's birds took eight full days of upwards of 14 hours each to complete their nest; they "began their working day as early as five in the morning, and they did not wholly rest from their labors until eight o'clock at night." They brought a load of material about every two or three minutes.
Dr. Harold B. Wood, who has sent me some notes on this subject, evidently agrees substantially with Professor Herrick on all the above points. A nest that he watched near Harrisburg, Pa., was built in six days. Dr., Dickey tells me that, from his observations, a pair of barn swallows will average 12 days in building a nest and will sometimes delay laying in it for two weeks after it is finished. They seem to prefer to repair and use an old nest rather than build a new one, so that often the same nest is occupied for a number of years, or a new one is built on the remains of the old one, or at least in exactly the same spot.
The size and shape of the nest vary greatly with its location; on a vertical surface the nest is roughly in the shape of a reversed half cone, the top being somewhat more than half a circle, and the lower end pointed; if built on a flat surface, the nest is more circular, like a phoebe's nest, and much shallower than the cone-shaped nests, but in such cases the birds often build mud walls along the flat beam for a foot or more, apparently for perches or to prevent the young from falling while exercising their wings. Nests built in corners or in the angles of braces are smaller and made to fit the spaces. The outer diameter of the circular top of the nest will average about 5 inches and the inner diameter is, fairly constantly, about 3 inches.
The composition of the nest consists mainly of dried mud mixed with grass and straws, and it is profusely lined with poultry feathers, mainly white ones. A nest dissected by Dr. Wood (1937b) "was found to contain, besides nearly seven and one-half ounces of dried earth, 1635 rootlets over one-half inch in length, 139 white pine needles, 450 pieces of dried grass, 10 chicken feathers, 4 pieces of wood, 2 human hairs and a piece of leaf and cotton, and a tablespoonful of minute pieces of rootlets and grass."
Horse hairs enter into the composition of many nests. Dr. Dickey tells me that he has seen swallows hover around stalls and disentangle the hairs lodged in cracks; these hairs sometimes make trouble for the birds.
Some nests are made without the use of mud; nests in narrow crannies or holes, with supporting floor and sides, do not need the mud foundation and are made of grasses, straws, feathers, and other available materials. James B. Dixon says in his notes: "The nests in the caves of the ocean walls are very unusual in that the birds are hard pressed for suitable mud and use a great deal of sea weed, with the results that the nests look like some old man with a beard, as the sea weed stringers hang down from the nest." These nests are lined with seaweed instead of feathers.
Eggs.--The barn swallow's set usually consists of four or five eggs; six eggs are fairly common, and seven are rare; as many as nine have been found in a nest, but these were probably the product of two females. The eggs are practically indistinguishable from those of the cliff swallow. They vary from ovate, the commonest shape, to elliptical-ovate, or rarely to elongate-ovate. The ground color is white, and the markings are in shades of bright reddish brown or darker browns, with sometimes a few underlying spots of pale lilac or drab. Some eggs are evenly covered with fine dots, more often sparingly than thickly, and others show numerous larger spots or small blotches scattered over the egg, or concentrated in a ring about the larger end; rarely an egg is nearly immaculate. The measurements of 50 eggs average 18.8 by 13.5 millimeters; the eggs showing the four extremes measure 21.1 by 13.5, 20.8 by 15.2, 17.3 by 13.2, and 19.0 by 12.2 millimeters.
Young.--Much study has been given to the development, care, and behavior of young barn swallows, and a number of excellent articles have been published on the subject. Since space will not permit extensive quotations from these, I shall attempt merely a condensed summary of the facts, with a few direct quotations. Readers who would like to make a more detailed study of the subject are referred to the following more important papers: E. M. Davis (1937), Dayton Stoner (1935 and 1936a), Wendell P. Smith (1933 and 1937), and Harold B. Wood (1937a and 1937b).
Most observers give the period of incubation as either 15 or 17 days, but some have placed it as low as 13 days; it probably varies some, with 15 a fair average. Both parents share this duty, changing places at frequent intervals, averaging about every 15 minutes. Dr. Wood found that after the third day of incubation they changed at intervals of between 4 and 15 minutes; on the eleventh day the intervals ranged from 6 to 36 minutes. William Brewster (1938) says: "The change which took place on an average of over every fifteen minutes was effected with singular adroitness. The incoming bird, twittering loudly, flew directly to the nest always aiming for the point where its partner's tail projected over the rim. . . . So quickly was it done that I doubt if a person looking down on the nest from above could have got more than the briefest possible glimpse of the eggs."
The female apparently incubates during the night, with the male perched near her. Two broods seem to be raised generally in a season in the more temperate portions of the bird's range. Dean Amadon observed about a dozen pairs nesting in a barn in New York state, and tells me that "Almost exactly 50 percent raised a second brood. Usually pairs that used an old nest, constructed in previous years, would raise two broods; those that built a new one only one."
The young remain in the nest 18 days (Smith), 19 days (Wood), or 23 days (Herrick) and are fed and cared for constantly by both parents. They are not always fed in regular rotation; generally the one that seems most anxious for food is fed first. Probably the youngest birds are fed on regurgitated food, though this does not seem to have been definitely observed; they are, however, known to be fed on fresh insects at an early age, mostly very small insects. The parents eat the fecal sacks for the first few days, but later they carry them away until the young are about 12 days old, when the young are able to turn around and void their droppings over the edge of the nest.
Among the developments observed by Mr. Smith (1933) "was the opening of the eyes, a gradual process, beginning on the 5th day and being completed on the 8th. The use of the wings progressed from their being fluttered on the 9th day to short flights when removed from the nest on the15th, although even on the latter date dependence was still largely placed upon crawling and hiding as a means of escape. Fear first became manifest at nine days of age, when, at the alarm note of a parent the young would retreat from the rim of the nest and crouch down in the bottom."
As the plumage begins to grow, the young swallows become more active, wagging their heads about and hanging them out over the edge of the nest, as if in imminent danger of falling, though few such accidents occur. When about 15 days old they begin active preening, scraping off the scales of the feather sheaths. At length the time comes for them to leave the nest; the parents urge them to do so by refusing to feed them in the nest and by flying back and forth near the nest, enticing them to leave. After leaving the nest they remain in the vicinity for several days, returning to the nest each night.
Dr. Charles W. Townsend (1920c) writes of some young birds that he watched: "At times they rested in trees and were fed by the parents, sometimes they were fed in mid-air, but doubtless they did some insect catching on their own hook. At six o'clock they were all back in the nest and being fed by the parents. For four more days this was repeated. The young left in the morning but returned to the nest at night, generally going and coming together. On the fifth night only two returned and after that they occupied the nest no more. I imagined I saw the family party several times, however, as a group of six or seven barn swallows flew past, and occasionally they would fly around under the porch, the adults pouring forth their souls in song."
Plumages.--The young nestling is scantily covered with "smoke gray," or darker, natal down on the forehead, occiput, scapular region, and middle of the back; this down persists later on the tips of the juvenal plumage and has not wholly disappeared on the head when the birds leave the nest.
The juvenal plumage is much like that of the adult but is duller and paler. The sexes are alike. The upper parts are dull iridescent green, more browning on the crown, with reddish brown edgings on the nape, rump, and wing coverts; the under parts are pale cinnamon, tinged with russet on the throat, with an incomplete dusky or black band across the jugulum; the tail feathers have large subterminal white spots, the outer pair broadly rounded at the tips and reaching less than an inch beyond the central pair. This plumage is worn until the birds leave for the south. Apparently a complete molt takes place while the birds are in the south, probably beginning with the body plumage in the fall and completed with the molt of the flight feathers later in winter or early in spring; but we do not know much about how this takes place, for adequate material is lacking. We do know that the birds return in spring in a plumage that is practically adult, with the long, attenuated lateral tail feathers extending fully one and one-quarter inches beyond the middle pair, with the metallic purplish feathers of the jugular band, the chestnut throat, and the darker cinnamon abdomen. All these colors are more or less variable, even in adults, where the sexes are often very much alike, though the female is usually much paler than the male. Adults have one complete annual molt, the postnuptial, after they leave for the south; this is probably accomplished somewhat earlier than that of the young.
The barn swallow has been known to hybridize with the cliff swallow ***.
Food.--Professor Beal (1918) analyzed 467 stomachs of the barn swallow and found that the food was made up of 99.82 percent animal matter and 0.18 percent vegetable. "Diptera are evidently the choice food of the barn swallow. They average 39.49 percent of the food, or more than twice that of any order of insect." They are mostly allied to the common house fly, but include long-legged crane flies (Tipulidae), horse flies (Tabanidae) and several robber flies (Asilidae), which are said to be very destructive to honeybees.
Beetles of various families amount of 15.63 percent. The useful beetles, those that prey upon other insects, predaceous ground beetles (Carabidae) and ladybirds (Coccinellidae), amount to only 3.4 percent. All the remainder of the 80 species of beetles are "most of them harmful and some exceedingly so." These include the May beetle family (Scarabaeidae), mostly small dung beetles, various weevils, including the cotton boll weevil and the rice weevil, and the "destructive engraver beetles that do so much damage to timber."
Hymenoptera other than ants make up 12.82 percent, consisting of bees and wasps, but only one honeybee was found, a drone. "Ants are eaten by the barn swallow to the extent of 9.89 percent of the food, some stomachs being entirely filled with wingless species." Himiptera formed 15.1 percent, including stink bugs, leaf bugs, plant lice, and chinch bugs. Other items include a few Lepidoptera, 2.39 percent, mostly adults, still fewer grasshoppers and crickets, 0.51 percent ; dragon flies, 4 percent; and a few May flies, spiders, and snails.
"All the vegetable matter found was contained in six stomachs, but it was real food in only four. One of these revealed seeds of the elderberry (Sambucus) and of Cornus sericea. Vegetable food in this stomach made up 75 percent of the contents. The second stomach held a single kernel of buckwheat, the third a root or bulb, and the fourth two seeds of Croton texensis."
Swallows probably spend more time in the air than any other group of passerine birds, not excepting the flycatchers; consequently nearly all their food is captured while they are on the wing. They catch more flies than the flycatchers because, in their swift and tireless flight, they cover much more open country, over fields, meadows, marshes, and ponds, whereas the flycatchers are limited to such insects as happen to fly near their perches.
Barn swallows follow the farmer while he is plowing to catch such insects as he stirs up and even alight on the ground to pick up others. They may often be seen coursing back and forth among moving cattle or sheep, gleaning the insects that these animals disturb. Anyone who has walked through a field of waving grass has noted how the swallows follow him, catching insects in the air or picking them deftly from the grass tops. Mr. Forbush (1907) says: "It is particularly serviceable about grass fields. The moths of the smaller cutworms, those of Arctians and Crambids, are among the injurious insects that it gleans when flying low over the grass. . . . Codling moths, cankerworms moths, and Tortricid or leaf-rolling moths are gathered from the orchard." Thus in many ways these swallows are most useful to the farmers.
Dr. Dickey says: "There are known instances of vegetation having been saved on farms where barn swallows had breeding colonies, while neighboring farms, without swallows, were about denuded of plant life," in West Virginia, during a recent drought.
Behavior.--What is more graceful or more pleasing to watch than the flight of the barn swallow? The flight of the albatross, as it mounts from the trough between seas over the crest of a wave, is effortless, powerful, majestic; the soaring flight of the eagle and the spirited dash of the falcon are inspiring; and the swallow-tailed kite charms the observer with its grace. Few of us are privileged to see these masters of the air except on rare occasions, but, if we could only learn to appreciate our familiar little friend of the barnyard, we would see that his powers of flight compare favorably with the best of them. His flight is fully as graceful as that of the kite, which after all is only a glorified swallow; it is as swift for his own purposes as that of the falcon; and, in dashing through the narrow openings to his nesting places, he shows as much control of his wings as does the albatross in skimming the waves. His poise and grace on the wing are unsurpassed.
Wilson (1831) made some interesting calculations as to the number of miles that the barn swallow flies in its lifetime; assuming that it flies at the rate of a mile a minute, for ten hours a day, and lives ten years, it would fly 2,190,000 miles, or over 87 times around the earth; this is doubtless too high an estimate, but it is impressive, even if greatly discounted.
The barn swallow is a gentle, harmless creature that attends strictly to its own affairs and seldom troubles its neighbors. Like all birds, it defends its nesting territory against intrusion by phoebes or other swallows that attempt to occupy its nesting site; and it doubtless attempts to drive away predatory birds or mammals that threaten its eggs or young. I once saw a pair of barn swallows chasing and attacking a sharp-shinned hawk that came too near their nesting place; the hawk retreated, but the swallows followed it high up into the air and it finally tired of their attacks and disappeared. Dr. Townsend (1905) "heard a great outcry among some swallows and found a company of Barn Swallows mobbing a jack rabbit as he bounded off on an upper part of the beach," at Ipswich, Mass.
Swallows seem to show a playful spirit in many of their activities; they seem to enjoy the sport of gathering feathers for their nests; many a country boy has tried the fun of throwing feathers into the air and watching the birds scramble for them; the swallow seldom misses its aim, but, if the feather is dropped, it is immediately seized by another bird; often the feather changes "hands" several times before it reaches the barn; sometimes it seems as if the feather were dropped again and again in a spirit of mere play.
Swallows are sociable birds and often gather in large mixed flocks--barn, bank, tree, and cliff swallows--and seem to enjoy the sport of flying about and showing their mastery of the air, apparently for the pure joy of flying. Dr. Townsend (1920c) writes: "One September day at sunset a flock of many hundreds if not thousands of these birds were alighted on the bushes, fence rails and wires near the waters of Sagamore Pond. They arose with the roar of many wings, and turning first their dark then their white surfaces to the observer, swirled about in irregular groups. Then they all flew close to the water, and every now and then hurled themselves at it so that the quiet surface of the pond was pitted with splashes as from a bombardment. Their heads, backs and wings were soused in the water, which they shook off in showers as they arose. At times they would dip lightly several times in succession."
It is a familiar sight late in summer to observe long lines of swallows of several species sitting on the telephone wires along the roads; here they sit and rest or preen their plumage, stretching one long wing down until its tip reaches beyond the tail as the plumage is dressed beneath it; sometimes one will scratch its head with its foot; but for the most part they sit quietly, enjoying one another's company and seldom quarreling unless the wires become overcrowded.
After the breeding season is over swallows become highly gregarious, as indicated above, and gather in immense flocks to roost at night in marshes or thickets of trees or bushes. W. E. Saunders (1898) describes such a gathering in a thick stand of willows near London, Ontario, as follows:
Passing these on the evening of August 4th of this year, I was attracted by the large number of Barn Swallows circling near it, which, as the night drew on, became more and more numerous, until I judged there were about 5,000 birds-- almost all Barn Swallows--in the flock. They flew at random until about 8 o'clock, only a few alighting in the roost before that time, but at 8:04 my notebook records them "falling like leaves," and by 8:05 half were settled. Their manner of descent was both interesting and beautiful, especially of those from the upper strata, for they were flying at all elevations from those just skimming the ground to those so far up that they could with difficulty be seen, and these latter, in descending at an angle of only 20 degrees from the perpendicular, performed the most beautiful aerial evolutions it has been my fortune to witness. Setting their wings for the drop, they would waver from side to side as they came, much as a leaf wavers, but of course with many times greater speed. . . .
Within five minutes of the time of the first general movement, barely a tenth remained in the air, and their voices, which are so liquid and soft when heard singly, became one of the harshest dins imaginable--English Sparrows could be no worse--and it certainly sounded as if they were all talking at once.
At 8:12 only a few are recorded as remaining, and at 8:19 the last one went in.
Swallows have been seen at sea, far out from land, and may occasionally be forced down; they cannot swim, of course, but seem to be able to rise from the surface. Dr. Wood tells me that his son, Merrill Wood, saw a young barn swallow alight on the water of Narragansett Bay and, after a short rest, rise from the surface and fly away.
Voice.--Dr. Winsor M. Tyler contributes the following: "The notes of the barn swallow always seem to express happiness, in keeping with its joyous flashing across the sky. Kvik-kvik, wit-wit, he says, in short delicate, but energetic syllables, as he doubles and turns and twists through the air. When he shoots through the open doorway of the barn to his nest, he greets his mate and young with a friendly kivik, accented at the end--almost pronouncing the word, quick. Out of doors again, either coursing along on the wing, or perched on roof or wire, he entertains his family, or lets his irrepressible energy go, with a long pleasing song of many jumbled, bubbling, rapid notes, culminating with a queer, ecstatic trilling sound which Ralph Hoffmann (1904) aptly terms 'a very curious rubbery note.'"
To the above pleasing account might be added the tributes of many other admirers. Dr. Townsend (1920c) writes: "To my mind the Barn Swallow is one of our most delightful singers. His song is always full of charm, soft and lovely, devoid of all roughness. Besides delivering an individual song, he delights in singing in chorus. It is a sweet and cheerful song full of little trills and joyful bubbles of music, at times clear and sparkling, at times oozing and rubbery. Like the music of a brook, it flows on indefinitely. At times the old barn is permeated with its melody. . . . From the first day of their arrival in late April till the end of August and even into September this charming bird sings. Very few birds have such a long and continuous song season."
The barn swallow not only sings delightfully throughout a long season, but also through a long summer day. Horace W. Wright (1912) says that the twitter of this swallow is one of the earliest sounds in the morning awakening, and seems "to proceed at first from the birds on their night perches." His earliest record is 2:51 a.m., and the average of 11 records is 3:04 a.m.
Field marks.--The barn swallow is one of the best known and most easily recognized of our swallows. It is the only North American swallow that has a long, deeply forked tail, with white spots on the tail feathers, and rich brown or buffy under parts. The females are usually duller colored than the males, but not always. The young birds are much duller in color and the lateral tail feathers are shorter than in the adults, but the under parts are never white and the tail is always more deeply forked than in other species.
Enemies.--Probably more swallows perish from the effects of inclement weather than from any other cause; a prolonged, cold rainstorm drives insects to cover, the swallows are unable to obtain the necessary amount of their accustomed food, and old birds, as well as young in the nests, die from hunger and cold. The use of horsehair in the nests, in which the wings, feet, or necks of the birds become entangled, results in the death of some. House wrens have been known to puncture the eggs of barn swallows and appropriate their nests. English sparrows and phoebes contend with them for nesting sites and even drive them from their nests. As the swallow skims low over the surface of a pond, it may be caught by some large fish or bullfrog; Forbush (1929) gives an authentic account of such a case, from Mrs. Chester Bancroft, of Tyngsboro, Mass.: "There is a brook flowing through the Bancroft yard, in which lived an enormous bullfrog, which Mrs. Bancroft's daughter had been watching with interest during the summer of 1927. One day she saw the tips of a bird's wings protruding from the corners of his mouth. The frog was finally caught and relieved of what he had swallowed. It was a full-grown Barn Swallow."
I once had a large, black cat that was a great bird catcher; he would lie hidden in the tall grass and watch for passing swallows; one day I saw him leap into the air and catch a swallow, as it swooped low over the grass tops. Forbush (1929) says: "The appearance of a strange cat, a weasel or a Sharp-shinned Hawk, when the Swallow have young, is the signal for a concerted assault. I have even seen a lone pair of breeding birds drive both cat and weasel from the neighborhood of their helpless young."
The young in the nest are often attacked by parasites, such as the larvae of the Protocalliphora; the maggots of these flies are very destructive to the young birds of many species, attaching themselves to the eyelids, or entering the throats or nostrils, and probably causing the death of many young. Mr. DuBois tells me of how a barn swallow met its death by a very strange accident; in spite of its dexterity on the wing, it darted into the path of a flying golf ball and was killed by it.
Fall.--In the northern portion of its breeding range, where only one brood is raised, the fall migration begins early, or soon after the young are strong on the wing, probably early in August. Wendell P. Smith (1937) says of the birds that he studied at Wells River, Vermont: "Flocking evidently began about July 15, as flocks larger than family units were first seen on that date. Migration seemed under way by August 2, and local breeding birds seemed largely gone by August 18." In southern New England barn swallows are common enough in flocks all through August and part of September, but many of these may be birds that have come from farther north. The migration seems to be largely coastwise; we always see plenty of them on outer Cape Cod during late summer and early fall; they scatter out over the marshes, coursing about independently to feed on the millions of mosquitoes and flies; on windy days, I have often seen them resting in compact flocks on the "back of the beach" (ocean side), squatting low in the sand and all facing the wind.
They seem to prefer to migrate by day and, strangely enough, often against a strong south wind. Some of them fly high in loose formation, but oftener they move along within 100 feet of the ground or lower. They may often be seen moving along the coast line, or the bank of a river, only a few feet above the ground or water, in a steady open stream, all following the same general direction but without any definite flock formation. They have been seen at sea, and must regularly migrate across the Gulf of Mexico to reach their winter range in South America.
Dr. Winsor M. Tyler contributes the following observation:
"In the inland country of New England we see the last of the
barn swallows during the first week in September, often in small
parties, gathered on telegraph wires, resting on their journey, or
sometimes we see them in actual migration--a few birds,
inconspicuous, wide apart and silent, flying past on their way to
the south. I know a little valley, 10 miles from the sea, drained
by a narrow brook, which must lie directly in the swallows' path
of migration, for if I spend half an hour there early in September
and watch the sky to the north, I am almost sure to see a barn
swallow coming toward me. It cruises along at the height of a tall
tree, veering sometimes far to one side or the other, but holding,
in the main, a straight course, following the dip of the land.
Sometimes it is a lone bird, but sometimes before it is out of
sight, mounting up over the hill at the southern end of the
valley, a second or a third bird will appear out of the north and
follow, far behind, on the same invisible track. These are the
last barn swallows of the year. We shall see no more until, in
early May, they come jubilantly back to the farmlands."
Barn Swallow* Hirundo rustica
*Original Source: Bent, Arthur Cleveland. 1942. Smithsonian Institution United States National Museum Bulletin 179: 439-458. United States Government Printing Office