[Published in 1949: Smithsonian Institution United States National Museum Bulletin 196: 233-260]
The bluebird is well named, for he wears a coat of the purest, richest, and most gorgeous blue on back, wings, and tail; no North American bird better deserves the name, for no other flashes before our admiring eyes so much brilliant blue. It has been said that he carries on his back the blue of heaven and the rich brown of the freshly turned earth on his breast; but who has ever seen the bluest sky as blue as the bluebird's back? The early settlers in Plymouth Colony welcomed this friendly, cheerful songster, which reminded them of their beloved English robin redbreast, and they named it the "blue robin," an appropriate name still used among some children. And, as our Pilgrim fathers welcomed it over 300 years ago, so do we today greet with joy the coming of this lovely, gentle bird each spring. Dull indeed would be the man that did not feel the thrill awakened by the first glimpse of brilliant color in the orchard and the cheery warbling notes borne to our ears on the first gentle breath of spring!
Before the English sparrows came to crowd the bluebirds out, the latter came freely to nest in the boxes that we put up for them, or to occupy the natural cavities in the apple trees near our houses, even in the towns and villages. And the coming of the starling has driven them still farther away from our homes. So, now we must look for them in the open country, in the rural apple orchards, along the country roadsides, in open groves, and in burned-over or cut-over woodlands where there are plenty of dead trees and stumps with suitable hollows for nesting. They can be encouraged to remain, however, in any open region by putting up plenty of nesting boxes.
Spring.--The bluebird is a hardy bird; it does not go so far south in winter as most birds do, and it seeks the first favorable opportunity to return to its summer haunts. A few individuals may spend a mild winter in southern New England, but, as a rule, we may not expect to see the first arrivals here earlier than the first warm days in February; these are probably birds that have wintered not much farther south; and they may not stay long, as winter lingers in the lap of spring, late snowstorms and cold snaps may return and the venturesome birds are forced to retreat. But when the bluebirds come to stay, then we know that spring is really here. They are close rivals with the early robins and red-winged blackbirds, as harbingers of spring. W. E. Clyde Todd (1940) has expressed it very well, as follows:
Of all our birds, this soft-voiced harbinger of spring is one of the most eagerly awaited. When winter begins to yield at last to the warming touch of the returning sun; when several days of clearing skies and southerly breezes have loosened the ice-fettered streams, drawn the frost from the ground, and given a balmy tang to the air; and when all nature seems in an expectant mood, vibrant with a new hope and a new promise--the Bluebird returns. . . . Its soft, pleasing warble, like the gentle murmur of a flowing brook in soothing cadence, awakens a sense of well-being and content in each responsive listener.
Bluebirds are seen more or less in winter over so much of their breeding range that the spring migration is not easily traced. Probably there is a gradual northward trend throughout all the winter range, with periodical retreats and advances influenced by weather changes. On Mount Mitchell, in western North Carolina, Thomas D. Burleigh (1941) seems to have noted a definite period of transition, for he found it "fairly plentiful" there "during the early spring months in the cut-over area (6,000 feet), occurring then in small scattered flocks. Extreme dates of occurrence are February 20 (1931) and March 21 (1930). It may possibly breed sparingly at this altitude, although there are no actual records."
John Burroughs (1880) says:
In New York and New England the sap starts up in the sugar maple the very day the bluebird arrives, and sugar-making begins forthwith. The bird is generally a mere disembodied voice; a rumor in the air for two or three days before it takes visible shape before you. The males are the pioneers, and come several days in advance of the females. . . .
The bluebird enjoys the preeminence of being the first bit of color that cheers our northern landscape. The other birds that arrive about the same time--the sparrow, the robin, the phoebe-bird--are clad in neutral tints, gray, brown, or russet; but the bluebird brings one of the primary hues and the divinest of them all.
Many a disaster may overtake these hardy pioneers on their northward journey from the genial southland; perhaps they are more brave than hardy, for they suffer much, and many perish from the effects of sleet and snowstorms, and from freezing temperatures. Bagg and Eliot (1937) quote the following story from a Springfield, Mass., paper: "On March 28 a pair of Bluebirds came to the feeding station of Charles J. Anderson, 24 Eddywood Ave., Springfield, and after eating began to flutter and peck at the window. It was cold outside, so after talking to them through the glass, Mrs. Anderson let them in. The male was hardy, but the female manifestly required warmth. She was given warm milk to drink, and warbled her thanks. For three days, while the cold spell lasted, she returned periodically to get warm inside the room." They say that "Mr. Cross of Huntington has a photograph of twenty-two Bluebirds together which, caught in a heavy spring snowstorm, lived upon sumac berries and between feedings snuggled together, all fluffed up, on a small dead branch in the shelter of a building."
And Edward H. Forbush (1929) says that "in western Massachusetts and in Vermont during the late spring storms many bluebirds have died huddled together in hollow trees, where they sought refuge from fury of the gale. During a storm a lady in Stowe, Vermont, heard a bluebird calling in her living room and found two in the stove. They had sought shelter in the chimney and had come down the stovepipe."
Courtship.--The love-making of the bluebird is as beautiful as the bird itself, and normally as gentle, unless interrupted by some jealous rival who would steal his bride; then gentleness gives place to active combat. The male usually arrives a few days ahead of the female, selects what he considers to be a suitable summer home, and carols his sweetest, most seductive notes day after day until she appears in answer to his call. Then he flutters before her, displaying the charms of his widespread tail and half-opened wings, warbling in delicious, soft undertones, to win her favor. At first she seems indifferent to the gorgeous blue of his overcoat or the warm reddish brown of his ardent breast. He perches beside her, caresses her in the tenderest and most loving fashion, and sings to her in most endearing terms. Perhaps he may bring to her some delicious morsel and place it gently in her mouth, as an offering. Probably he has already chosen the cavity or box that he thinks will suit her; he leads her to it, looks in, and tries to persuade her to accept it, but much persistent wooing is needed before the nuptial pact is sealed. In the meantime a rival male may appear upon the scene and a rough and tumble fight ensue, the males clinching in the air and falling to the ground together, a confusing mass of blue and brown feathers struggling in the grass; but no very serious harm seems to have been done, as they separate and use their most persuasive charms to attract the object of their rivalry. At times, a second female may join in the contest and start a lively fight with her rival for the mate she wants. John Burroughs (1894) gives an interesting account of such a four-cornered contest, too long to be quoted here, in which the female of an apparently mated pair seemed to waver in her affections between her supposed mate and the new rival; and the latter seemed to have left the female of his first choice to win the bride of the other. However, after a much prolonged contest, the matter seemed to be satisfactorily settled, for two pairs of bluebirds finally flew off in different directions and started up housekeeping without further trouble.
But bluebirds are not always constant in their nuptial ties, even when they have raised a brood together successfully. Mrs. Nice (1930a) cites a case in which a male had a different mate for the second brood but returned to the first mate for the third brood, all in the same year. Seth H. Low (1934) has indicated, by banding at a station on Cape Cod, Mass., that bluebirds select different mates in successive seasons; he says: "In 1932 eight pairs of adults were banded at the Station. From two pairs neither bird returned. One adult from each of five pairs was captured nesting with a new mate. As it cannot be proved that each of the former mates were alive, it cannot be concluded that these birds were inconstant. Both adults did return from the eighth pair, but each took a new mate. No conclusions on mating constancy can be drawn from this one case."
T. E. Musselman (1935) writes: "During the first nesting period in 1935, I banded eighteen mothers. During the second nesting I found that none of these birds were in my nests, which leads me to believe that the mother bluebirds probably travel a number of miles between the first and second nesting and probably fly in small irregular bands with the broods of young birds. The second nesting is carried on by stray mothers which have formerly nested elsewhere."
If a male bluebird loses his mate, he quickly secures another. Dr. T. Gilbert Pearson (1917) tells of one that had three mates in a single season. The first two females were killed by a cat, but the third raised a brood, for "on a sunny hillside in the garden the cat was buried."
Nesting.--In the early days of my egg collecting, from 1880 to 1900, we always looked for bluebirds' nests in natural cavities in apple trees in old orchards, and fully 80 percent of our nests were found in such situations, though we found some in natural cavities in other trees and in old woodpecker holes. Nesting boxes were not so plentiful in those days as they are today. Two changes have taken place during the present century that have greatly modified the nesting habits of these birds. The old, decrepit apple trees have been pruned of their dead branches, the cavities have been filled, or the old trees have been removed entirely, thus destroying many favorite nesting sites for bluebirds, tree swallows, and some other birds. The old orchards have been replaced by new, young orchards, in which the trees are regularly pruned and sprayed, which is better for the apple crop but not so good for the birds. Furthermore, there has been an immense increase in the number of bird boxes put up by appreciative bird-lovers and by agriculturists who are now well aware of the economic value of the birds. The result has been that the bluebirds were not slow in adapting themselves to these two changes and in adopting these better types of nesting sites. So that, at least in settled communities, a great majority of the bluebirds now nest in the boxes.
To get the best results the boxes should be set on poles at no great height above ground, preferably between 8 and 12 feet, and in the open; to keep out starlings, the entrance hole should not be over 1 1/2 inches in diameter; even then, there will be competition from tree swallows or house wrens, but the bluebirds are usually more than a match for these two.
Several large nesting projects have been reported where numerous boxes have been erected to encourage the birds to breed. One of these, part of which I have seen, centers around the great bird-banding station of Dr. Oliver L. Austin, at North Eastham, Mass. There are over 500 boxes in this project, chiefly around the main station, but also scattered at various distances away, from 2 to 9 miles north and south along the outer arm of Cape Cod. Most of the boxes that I have seen are erected on slender poles, within reach of a man standing on the ground, along lines of fences and around the edges of fields, bogs, marshes, and ponds. Most of them have been occupied by tree swallows, but many by bluebirds.***
For seven or eight years Dr. T. E. Musselman (1939) has been building bluebird boxes in quantity and erecting them on fence posts along the hard roads leading into Quincy, Ill. "The idea appealed to the popular fancy immediately," and he has received much help from school students of conservation and others. It took about 50 boxes to cover 38 miles of one road, and he placed 150 boxes along another 68 miles of road. He says: "All of these boxes are standardized, have removable tops, and by the time the entire project is complete will include nearly one thousand Bluebird boxes. Magazines and newspapers have printed copies of my plans and because of such publicity I feel that in many sections of the country, similar projects will be carried on." In a previous paper (1935) he says: "In no case did two birds nest closer than a quarter of a mile." His nests were placed from 3 feet to 10 feet above the ground, apparently mostly nearer 3 feet than 10, "and on posts away from human habitation. If the box is placed on the pasture side of a post away from the wires, cows use the box to scratch their backs, so I try to attach them to the wire side of the post. This protects them from cattle and likewise makes it impossible for cats to molest them." He gives further useful instructions for making the boxes, to which the reader is referred.
Mrs. Amelia R. Laskey has sent me some elaborate notes on another interesting and successful project, of which she says: "Nest boxes for eastern bluebirds have been placed in Percy Warner Park and the adjoining Edwin Warner Park to increase the numbers of this species around Nashville, Tennessee. Starting in 1936 with 26 boxes, others have been gradually added so that 63 have been available the past three years." In one of her published papers (1939), she says that Percy Warner Park "consists of 2141 acres. . .much of it wooded hills, with many miles of winding automobile roads, bridle paths, and hiking trails, interspersed with picnic grounds, shelter houses, and homes of park employees. On the outer boundaries are numerous meadows, bordered on one or two sides with narrow thickets of trees and undergrowth. These meadows provide excellent sites for the Bluebird nest boxes that have been placed there. . . . Of the 37 nest boxes available in 1938, 36 were used at least once by Bluebirds, with a total of 104 sets or 460 eggs laid, an average of 4.42 per nest."
A. Dawes DuBois has sent me his data for 15 nests, observed in Illinois, Minnesota, and New York. Five of these were in bird boxes, three in holes in fence posts, two in hollows in apple trees, two in other tree cavities, two in old woodpecker holes, and one was in a telephone pole.
M. G. Vaiden writes to me from Mississippi: "This bird is a fairly common nesting bird in the hill section of our state, especially from the central hills to the northward until reaching the Tennessee line. They select any suitable site where they think it possible to hide a nest, as a gate post and natural cavities in trees, and I found a nest in a drain pipe, where they were stacked for use and some 6 feet high. The bluebirds selected a pipe near the top of the pile."
Bluebirds have been known to nest in a number of other unusual places, such as empty tin cans or jars, in open hollows in the rotten tops of posts or stumps, and more than once in cliff swallows' nests, even in active colonies. Dr. Charles W. Richmond sent me, long ago, a clipping (Putnam and Wheatland, 1866) which reads as follows: "At the depot, the signal master called the attention of a number of the members to a pair of Blue Birds which had built a nest in one of the signal balls, from which a piece of the canvas had been torn. These birds, after raising one brood of young, had made another nest, by the side of the first, in which they had laid the eggs for a second brood. The signal ball, in which the nests were made, was lowered and hoisted about fifty times a day. The birds flying out as soon as the ball commenced its descent, and, alighting upon a fence nearby, would wait patiently for it to be hoisted again, when they would at once return to their nest."
Another railroad nesting site is mentioned by Charles R. Stockard (1905); it "was the hollow iron coupling of a flat car which stood for many weeks on a side track. The old style link and pin couple had a long hollow neck and back; in this neck a Bluebird had built its nest and deposited a set of five eggs." A. L. Pickens writes to me that he "once found a bluebird's nest in a cavity in a steep earthen bank, some such a place as is usually frequented by the rough-winged swallow." Dr. Thomas S. Roberts (1932) tells the following interesting story of some very persistent bluebirds:
Many years ago there stood on the campus of the State University at Minneapolis two cannons, which were used every morning in artillery drill, and from which blank charges were frequently fired. A pair of Bluebirds selected one of these guns as a nesting site. The nest was accordingly built but of course was removed next morning. This went on for several successive days, the nest built one day being destroyed the following morning. At length one morning the cadet whose duty it was to charge the gun failed to observe whether or not the nest was there and rammed down the cartridge with a will. When he tried to fire the gun, of course it would not go off; so the load was drawn and an examination disclosed the nest and the female bird jammed into a scarcely recognizable mass against the breech. Promptly the male secured another mate and the following morning the usual nest was in the gun. This continued for a day or two, when the cannon was stored for the season in a shed near by and a cavity in an adjoining tree was chosen for the nest, where peace reigned.
At least two combination nests have been reported. B. S. Bowdish (1890) mentions a bluebird's nest in the top of an old stump that held four eggs; under this in the same cavity was a nest of eight young mice. "The mice had access to their nest through a small hole in the bottom of the stump, and nothing separated them from the eggs but the material of the two nests." And Mr. Todd (1940) quotes an anecdote by J. Warren Jacobs concerning a bluebird appropriating the finished nest of a Carolina chickadee: "The nest was in two parts; one constructed by the Chickadee, and the other, which was the top story, was made by the Bluebird. The first story contained two [eggs] of the Chickadee, and in the next were five eggs of each species." I once found a flicker's egg in a bluebird's nest, together with five eggs of the bluebird; and in the same orchard there was a flicker's egg in a tree swallow's nest, with five deserted eggs of the swallow.
The nests of the bluebird are poorly and loosely built structures; this is probably all that is necessary in the snug cavities in which the nests are usually made, where a firmly built nest is not required. The nests are often made entirely of dried grass and weed stems, carelessly arranged; sometimes a few fine twigs are added; the lining may consist merely of finer grasses, or sometimes a little hair or a few feathers are added. The possible nesting sites are often pointed out by the male after he has attracted the female to his breeding territory, but she evidently makes the final choice. Both sexes help in building the nest, though most of the actual work on it is done by the female.
Wendell P. Smith (1937) made the following observations at his banding station at Wells River, Vt.:
Nest-building did not proceed with uniform speed, especially in the case of an early beginning. There seemed to be some correlation with the temperature, as cessation of activity coincided with lower temperature and resumption of construction began with the coming of warmer weather. The time required for a nest's completion differed in consequence. The shortest period recorded was four days, and the longest twelve days.
Material was secured within a radius of seventy-five feet of the nest, and much of it within less than half that distance. In one case dried grass was used, while in the other, dead pine needles were obtained from the ground near by. Observations showed that the female performed nearly all the work of collecting. Between the completion of the nest and the laying of the first egg some time intervened, usually two or three days.
Dr. W. T. Harper (1926) has published some detailed observations on the building of a second nest by a pair of bluebirds. He concludes with the following summary:
The most interesting points disclosed by these observations seem to be the following: First, the site for a second nest seems to have been selected while the first brood was still in the nest, and the male took the initiative in the selection. Second, the male laid the first foundation of the second nest, but the female did practically all the work while the male acted as watchman or boss. Third, work was faster at the beginning of the building operations and, as finishing touches had to be added, the work became constantly slower. Fourth, parts of four days were required to build the nest, most of the work being done between 6:30 and 10 a.m. Fifth, at least two hundred and eighty-nine trips with nesting material were made by the female, the last fifteen of which were from a distance with material of fine texture, while the others were from less than 50 yards, with one or more pieces of dead grass. Sixth, the old birds, with young of both broods, returned to the vicinity of the two nests after an absence of about a month, and the old birds evidenced great interest in the second nesting site and showed some jealousy when the young approached it too closely.
Ora W. Knight (1908) says: "Nest building is participated in by both parents, and I have known of a nest containing the full complement of eggs just seven days after the birds began building, indicating that the nest was completed in three days and an egg laid daily thereafter."
Henry Mousley (1916) "once witnessed a pair of these birds drive out a Hairy Woodpecker from a half completed nesting hole it had made, and after gaining possession of it they immediately set to work building a nest which was completed and four eggs laid in the remarkably short space of six days."
Alexander Sprunt, Jr., has sent me the following account of an unusual nesting site, as observed by Prof. Franklin Sherman, of Clemson College, S.C. Professor Sherman writes: "The nest is saddled on a horizontal limb of an oak, at about 12 or 15 feet above the ground, and about 15 feet out from the trunk of the tree, which is in the front lawn of the college hotel building, almost overhanging a much-frequented street or road. One or two small twigs give support to the nest, but it is not in any fork of the main limb--it is saddled on the limb itself, which is about 1 1/4 inches in diameter at the nest. During my stay of about 20 minutes the adult female made two visits to the nest and fed the clamoring young."
Eggs.--The bluebird may lay anywhere from three to seven eggs to a set; as small a set as three is unusual, five is a much commoner number than four; six eggs are often found, but sets of seven are rare. The eggs are ovate or short-ovate and are somewhat glossy. They are normally very pale blue or bluish white and always, as far as I know, are unmarked. Numerous sets of pure white eggs have been reported; Dr. Musselman (1935 says: "In 1935 I was able to reach definite knowledge of the percentage of white eggs laid by Bluebirds. Of the 730 eggs recorded, 40 were albinistic in nature, or a total of 5.48 percent. Fifty percent of these white eggs hatched and the young were banded, and I am hoping that some of the young birds may return to this vicinity next year which will allow me to determine whether the trait of laying albinistic eggs is inherited." His hope was realized, for in his later paper (1939), he states: "This year [apparently 1938] I had the return of the first young female bird which had developed from a white egg laid in one of my boxes. . . . Imagine my delight in recording six albinistic eggs laid by this second generation bird. Of course, this one case is not sufficient to justify the conclusion that all female Bluebirds which hatch from albinistic eggs will in turn lay white eggs."
Mrs. Laskey, at Nashville, Tenn., has thrown considerably more light on this question of inheritance; I quote from her manuscript notes, as follows: "A number of individuals have laid white eggs, but there has been no evidence as yet to show this to be an inherited trait in this group. No. 36-146599, hatched April 1937 from an albino egg, was found in 1939 laying blue eggs. No. 38-121000, banded as an adult on April 6, 1939, was then incubating six white eggs. In 1940, one of those hatched from this set, N 6, laid five blue eggs in the adjoining meadow. The following year N 6 had moved to the next meadow, laying six blue eggs in the second nesting period. From this hatch, N 22 was found in 1942 as she incubated six blue eggs. Thus, daughter and granddaughter of the white-egg-laying female were laying normally colored eggs.
"Five birds, known to have been hatched from blue eggs, laid white eggs (N 1, N 11, N 13, N 18, N 21). Only one, N 11, was found in two seasons. In April 1940, at 253 days of age, she began her first set of five in the box where she had been hatched from a set of four blue eggs. For the season she laid 5-5-5-4 white eggs, with only the third successful. She deserted her first two sets soon after completion and the young of the fourth set when they were five days old. She reappeared in the box in March 1941, laying five albino eggs, one blue-tinged. Four young were raised; one egg was sterile. On May 6 she began her second set of five white eggs but disappeared at the time this set was hatching.
"In 1942 there were more white eggs laid than in any previous season. They consisted of three sets of four, eight sets of five, two sets of six, and one set of seven. This total of 71 white eggs was 9.1 percent of the 774 laid this season. Incidentally, sets of seven bluebird eggs are rare; the 1938 and the 1942 sets are the only records in the Nashville area."
The bluebird is a persistent layer; if a set of eggs is taken, another will be laid within a very short time, as the two following accounts will show. Guy H. Briggs (1902) reports taking five sets of white eggs from one pair of birds during one season in a Maine orchard; the sets were all of five eggs, which he described as smooth and glossy, like woodpeckers' eggs. The sets were taken on May 1, May 27, June 13, June 24, and July 6, the nests being taken with the sets. Two of the sets were in the same cavity in an apple tree, and two others were in the same nest box. Between the last two dates only 11 days were required to build the bulky nest and lay five eggs. The bird had about half incubated the first three sets, but the last two sets were perfectly fresh. Thus, in about 76 days the birds had built five bulky nests and laid 25 eggs.
Arthur T. Wayne (1910) had an experience that almost equaled the above record. At Mount Pleasant, S.C., he took three sets of white eggs from a single pair of birds in one season, on March 30, April 12, and May 6; this bird laid another set late in May, and these were allowed to hatch. The interval between March 30 and April 12 was a short time in which to build a nest and lay four eggs.
The measurements of 50 eggs in the United States National Museum average 20.7 by 16.3 millimeters; the eggs showing the four extremes measure 22.9 by 15.8, 20.3 by 17.8, 17.8 by 16.0, and 22.4 by 15.2 millimeters.
Incubation.--The period of incubation is generally conceded to be about 12 days, though in some cases it may be a few days longer. The young birds remain in the nest 15 to 18 days, according to various observers, but probably the former figure is near the average. Both of these periods are evidently more or less variable according to circumstances. Mr. Smith (1937) noted that incubation "usually began with the completion of the clutch, but one instance was recorded where it began with the laying of the fourth egg in a complement of six. Of nine successful incubations of the two broods, the period consumed 14 days in four instances, 15 days in three, and 13 and 16 days respectively, in two instances."
Incubation is performed mainly by the female, but the male assists in this duty to some extent. Mr. Smith (1937) says:
In one instance the male was seen to take his mate's place upon the eggs three times in the course of three hours. The male of No. 2 pair fed his mate at intervals and maintained the semblance of a watch during her absence for food. Often the male would fly to the box, or a near-by limb, uttering rapid call notes, whereupon the female would fly out and away for feeding. The male did not always remain near until his mate's return, but not infrequently he left shortly after the departure of the female. Absences, from meager observation, varied both in frequency and in regard to length of time. One nest was under observation from 3:15 to 5:30 p.m., and schedule is as follows: Female left at 3:27, returned at 3:35; remaining on the nest until 3:52. At 3:57 the male entered the nest and incubated until 4:17, when he left. At 4:18 the female returned to stay until 4:25. The male returned to the nest at 4:26, staying until 4:33 and returning again three minutes later for another period on the nest, which lasted until 4:48. The female entered the box at 4:59, and remained until 5:16. After four minutes absence, she came back and was still on the nest at the close of the observation period, ten minutes later. The male of No. 1 pair was not seen to take any part in the duties of incubation, although considerable time was spent in observation, three and a half hours being spent at one sitting.
The male of No. 1 pair was not seen to feed the young. . . . The male of No. 2 pair, on the other hand, was particularly active and during some of the observation periods fed the young more often than the female did. The brooding of this pair was carried on exclusively by the female so far as we could learn. [During one hour, from 2:09 to 3:09 p.m.] the male brought food at 2:34:30, 2:37, 2:45, and 2:58:30. Total feedings for the interval were nine, five by female and four by male, and brooding lasted twenty-seven and a half minutes divided into five separate periods. This may be compared with an hour's observation five days later, the period extending from 2:54 to 3:54 p.m. Nine feedings occurred within this interval also, but six were by male and three by female and the brooding occupied twenty-nine and a half minutes divided into two separate intervals. . . .
In general the period passed by the young in the nest was eighteen days; one exception occurred in the case of No. 2 pair in 1933, when the first brood of four left the nest after seventeen days.
A brood watched by Mr. DuBois were in the nest just 15 days. And Ora W. Knight (1908) says: "The parents take turns in incubating and the eggs hatch in twelve days, the young leaving in fifteen days after they are hatched. Both parents feed them and carefully take away in their bills all the excrement voided by the young." Mrs. Laskey (1939) states that "the only Nashville record of a brooding male Bluebird is that of Simpson in April and May of 1937 when one individual was captured twice in a mail box on a nest containing eggs."
Mr. Smith's (1937) studies of the development of young bluebirds show that on the first day they varied in length from 31 to 41 millimeters; and that at the time of leaving, the 17th or 18th day, they measured 125 to 130 millimeters in length. "The eyes usually began to open on the 4th day, but in one instance this was delayed until the seventh day. Completion of the process required from three to five days. Tail-feathers appeared on the 8th day. Primaries became noticeable on the 4th day."
Mrs. Laskey gives the following information on the success of hatching and rearing of the young, based on her study for seven years: "A careful analysis of the nesting data, accumulated through regular visits to the boxes, indicates that only 1,569 eggs of the 3,512 laid have been successful to the point of survival of the young to the age of 16-17 days when they normally fly from the nest. This is 44.67 percent of the total number laid and corresponds to percentages for birds building open nests. It is markedly lower than for hole-nesting species." Mr. Low's (1934) record for efficiency was decidedly better, varying from 62.7 to 87.5 percent.
Mr. DuBois gives the following account of young bluebirds leaving their nest in a fence post: "On June 19 the young were leaving their nest; only two remained within. I spent most of the afternoon trying for more photographs. After a long wait the male flew to a trolley bracket some 60 or 70 feet from the nest and sat there, and on the trolley wire, singing to the nestlings to come out. He kept this up for a long time. Occasionally a youngster would look out of the hole. They were hungry; they called to their parents in the musical young bluebird voice. But all afternoon the parents refrained from going to the nest to feed them. They merely came occasionally to try to coax the young ones out, by flying past, or by singing to them from some little distance. Finally, one of the youngsters--the one that had sat, two or three times, in the entrance way to look around--scrambled out on to the side of the leaning post, climbed part way around it, and flew across the car track to find a landing place on a horizontal guy cable, against a tree. Both parents fed it immediately; soon they returned and fed it again." He caught the young bird and returned it to the nest, but it came out again within a few seconds, flew over the pasture, and alighted on the ground. During the afternoon the parents had been busy feeding the other young that had left the nest earlier and were in trees. The last youngster was still in the nest when he departed.
Bluebirds almost always raise at least two broods in a season, or at least attempt to do so; in many cases three broods are raised. As soon as the birds of the first brood are on the wing, the male takes charge of them, feeds them and teaches them to feed themselves. And the female immediately gets busy with her second nesting, either with the same mate or with another; as mentioned above, only a few days are needed to build the second nest, or lay the eggs in the same old nest, which has been renovated, if necessary. By the time the second brood is hatched the young of the first brood are well grown, are still in the general vicinity of the nest, and are able to assist in the feeding of the second brood of young, as has been frequently observed. After all the broods are fully grown, the family group keeps more or less together in the general vicinity of the nesting site until the time comes to wander about in fall, preparatory to migration.
Many yearling birds return the following spring to nest in the general vicinity of their birthplace. Mrs. Laskey says: "Forty-two females, banded as nestlings, have returned to nest in the parks; also one banded elsewhere nested in the park, five miles from her birthplace. Numerous mated males, banded in the nest, are seen at the nests. The first eggs of 23 birds were laid at ages of 243 to 370 days, average 312. Egg-laying started on the average date of March 27 (1938 to 1942), nine days later than a group of 27 birds, two or more years old. Size of sets did not differ with age, five being the average. Late and early hatched birds laid at approximately the same time the following spring."
Plumages.--Mr. Smith (1937) describes the natal down as "dark mouse gray." The young bird is in practically full juvenal plumage when it leaves the nest, except for the short tail. The two sexes are distinguishable in this plumage by minor differences. Dr. Dwight (1900) describes the juvenal plumage of the young male bluebird as follows: "Above, slaty mouse-gray, the back lesser, median and a few inner greater coverts with white guttate spots bordered with sepia, the crown and rump much grayer and unspotted but sometimes with obscure transverse barring. Wings and tail are dull azure-blue, the shafts and tips of remiges and rectrices dusky with faint whitish edgings; tertiaries and greater coverts edged with pale chestnut. Below, dull white, mottled on throat, breast and sides with sepia, the feathers centrally white bordered by the sepia and a rusty suffusion. Auriculars dusky mouse-gray mixed with white; lores grayish; conspicuous orbital ring pure white."
The young female is similar to the juvenal male, except that "the outer primary and outer rectrix have white outer webs, the blue is everywhere very much duller, and replaced with brown on the tertiaries and wing coverts, the edgings duller and the quills with duskier tips."
The first winter plumage is acquired by a partial postjuvenal molt, in August and September, the date depending somewhat on the date of hatching. This molt "involves the body plumage, wing coverts, tertiaries and tail, but not the rest of the remiges." This plumage is almost indistinguishable from the winter plumage of the adult male, though the colors are somewhat duller; Ridgway (1907) describes it very well, as follows: "Similar to the spring and summer plumage, but blue of upper parts slightly duller, more or less obscured on hind-neck, back, and scapulars, by brownish tips to the feathers, and cinnamon-rufous of chest, etc., more purplish or vinaceous in hue."
Dr. Dwight (1900) says of the first winter female: "In first winter plumage the blue is obscure and confined to the wings, tail and rump, the back is dull grayish chestnut, grayer on the crown. The sides of the head are gray and white mixed, the orbital ring white. Below, the throat, breast and sides are reddish cinnamon, tingeing also the grayish white chin; abdomen and crissum dull white."
The adult and first nuptial plumages of both sexes are acquired by wear, which removes the edgings and brightens the whole plumage. The following postnuptial molt, beginning about the middle of August, is complete.
Food.--In its food habits, the bluebird is one of our most useful birds. It does practically no harm to human interests and it destroys large quantities of harmful insects. In his analysis of 855 stomachs, taken every month in the year, Professor Beal (1915a) found that the food consisted of 68 percent animal and 32 percent vegetable matter. He says: Orthoptera (grasshoppers, crickets and katydids) furnish the largest item of animal food, amounting to a good percentage in every month, and in August and September aggregating 52.68 and 53.47 percent, respectively. The month of least consumption is January, when they amount to 5.98 percent, and the average for the whole year is 22.01 percent. . . . Beetles constitute the second largest item of animal food, and for the year average 20.92 percent of the diet. Of these, 9.61 percent are useful species, mostly predaceous ground beetles (Carabidae). Few birds exceed this record of destruction of useful beetles. . . . This destruction of useful beetles has been considered by some writers a blot upon the fair name of the bluebird." Various other beetles of a more or less harmful nature, such as May beetles, dung beetles, weevils and others, are eaten in lesser amounts.
Ants amount to 3.48 percent, and other Hymenoptera (wasps and bees) to only 1.62 percent of the bluebird's food. Only one worker honey bee was found in one stomach. Hemiptera (bugs) average 2.75 percent for the year; stink bugs predominated, and remains of chinch bugs were found in one stomach. Lepidoptera, in the form of caterpillars and a few moths, form an important and regular article of food, averaging 10.48 percent for the year, the third largest item of animal food. Other insects, spiders, myriapods, sowbugs, snails, and angle-worms, with a few bones of lizards and tree frogs, made up the remainder of the animal food.
Beal's analysis showed that "the vegetable portion of the eastern bluebird's food is largely fruit and mostly wild species. Practically all of the domestic fruit taken was in June and July. Cherries and raspberries or blackberries were the only fruits really identified, though some pulp may have been of cultivated fruit. The most important vegetable food of the bluebird is wild fruit. The maximum quantity is eaten in December, when it amounts to 57.64 percent. January comes next, but after that month the amount decreases rather abruptly to zero in May. . . . The average for the year is 21.85 percent. At least 38 species of wild fruits were identified and probably more were present but not recognizable." Seeds are eaten sparingly, and grain was found in only two stomachs. Miscellaneous matter includes seeds of sumac, both the harmless and the poisonous kinds, poison ivy and bayberry, amounting to 7.84 percent for the year. Beal includes long lists of insects and vegetable matter eaten.
Bluebirds obtain their food in the air, in the trees, and on the ground. In the air they are not so expert as the flycatchers and cannot catch the swifter insects, but they are often seen fluttering along near the ground after low-flying insects or darting out from a perch on some high tree to snap up passing insects, sometimes darting about with a hovering flight for a considerable distance from their perch. Francis H. Allen writes to me: "One September day I saw about a dozen of them thus for an hour or two, the air being full of dancing gnats." Once, he saw "a male feeding for a long time on the ground on a lawn, progressing in straight lines for considerable distances. He fed much as a robin does, but hopped instead of running and did not pull out worms."
In the trees bluebirds dart about among the foliage for flying insects, or pick caterpillars, katydids, and other insects from the leaves and twigs. Fruits and berries must be picked mainly from the trees and bushes.
But by far the greater part of their insect food, such as grasshoppers, crickets, beetles, etc., is found on or near the ground, and one often sees a bluebird sitting on some low perch, a fence post or wire, or some low tree, watching for its prey. Then it suddenly darts down, seizes something from the ground, and returns to its perch or another lookout point. Perhaps it may flutter down and, hovering just above the grass tops, seize a grasshopper and alight on the ground to eat it or return with it to its perch. Sometimes it stands on the ground and looks around, or actively searches for beetles or crickets; if its prey takes wing, the bird may flutter along after it and catch it in the air.
Behavior.--Bluebirds are generally regarded as gentle and lovable birds and rightly so, for such is their ordinary demeanor. If undisturbed they are friendly with their avian neighbors. But they can be aggressive, and even fierce in standing up for their rights against aggressors. In the competition for nesting sites they have often been known to compete successfully with English sparrows and tree swallows, attacking and driving them away when they attempted to usurp their nesting box. Other larger birds are often driven away from the vicinity of the bluebirds' nest; the male stands guard while the female is incubating, feeds her occasionally, and drives away unwelcome intruders, even human beings. Once, while I was introducing a young boy to the mysteries of bird study, we were vigorously attacked; one of our party had removed the female and was holding her in his hand; and while the boy was examining the nest the male flew at him so savagely that he lost his balance and fell flat on his back. Mr. DuBois had a bluebird fly at his head in a very determined manner several times while he was examining a nest with young; it did not actually strike him but came very near it. And Francis H. Allen tells in his notes of a similar experience; he writes: "The parents were very solicitous and very bold; whenever I approached the nest they swooped at me, making a 'clopping' noise with their bills and uttering a harsh chattering note. The male was the more active of the two in the demonstrations. I could hardly help dodging when he launched himself at my head."
William A. Taylor sends me the following account of a swallow-bluebird feud at the Moose Hill Sanctuary in Sharon, Mass.: "Each spring for years past these two species have fought for the possession of a particular nesting box just back of the house. As a rule, the bluebirds won out, but this year they were outnumbered, and the swallows held possession and the bluebirds were forced to take another box some 35 feet away. For a time peace seemed to prevail; but one morning, when the swallows had eggs and the young bluebirds were about to leave the nest, I became aware of a commotion about the swallows' box. As I watched, both male and female bluebirds emerged with swallow eggs, which they dropped to the ground. The swallows left the neighborhood but, much to my surprise, returned after four days and, finding the bluebird box vacant, laid a second clutch and brought forth their young on July 3. The bluebirds raised their second brood in the swallows' first box, thus resulting in a complete exchange of boxes."
Edward A. Preble refers to a swallow-bluebird experience at his boyhood home in Wilmington, Mass. A nesting box was made with two apartments, side by side. Each spring its occupancy was a matter of sharp contention. But one spring the battle soon ended by a compromise. The two pairs proceeded to build in adjoining rooms, and both brought our their broods in relative peace.
The bluebird, like many other birds, has been seen shadow boxing or fighting his own image in a window pane or other reflecting surface. John Burroughs (1894) gives an amusing account of such behavior. He tells a story related to him by a correspondent; a pair of bluebirds had a nest on the observer's porch and a pair of vireos had a nest with young in some lilac bushes but a few feet away; for several days the male bluebird was seen to feed the young vireos repeatedly, greatly disturbing the old vireos; his correspondent writes: "Sometimes the bluebird would visit his own nest several times before lending a hand to the vireos. Sometimes he resented the vireos' plaintive fault-finding and drove them away. I never saw the female bluebird near the vireos' nest."
With kind treatment and a little encouragement, bluebirds may become very tame, confiding, and friendly. C. F. Hodge (1904) tells an interesting story about how he trained a whole family of bluebirds, old and young, to become friendly with all the members of his family; he began coaxing them to his windowsill with mealworms, of which they seemed to be very fond, and finally had them feeding out of his hand.
The reader is referred to an interesting study of the territorial, nesting, and other behavior of the eastern bluebird by Ruth Harris Thomas (1946), which is published in too much detail to be included here.
Voice.--The bluebird is no great singer; he cannot begin to compete with the greater songsters of the famous thrush family; but his short contralto notes of greeting, as we hear them early in spring, are most welcome and pleasing to the ear, full of richness and sweetness, and even expressing affection. He really does not need to sing; his simplest notes are full of music and fully satisfy the hungry ears of the listener.
Aretas A. Saunders has sent me the following full description of the song: "The song of the bluebird is soft, sweet, rather short, and warble-like. It consists of three to eight notes grouped in phrases of one to three notes each, with very short pauses between them. It is repeated every few seconds, and frequently two different songs are alternated. In the latter case it often happens that one song ends with a rising slur and the other with a descending one, so that it gives the effect of a question and an answer: Ayo ala loee? - - - -alee ay lalo leeo!
"The song is never so loud as those of other thrushes. It varies less in pitch and between individual birds. The range of pitch, from 24 records, is only 4 1/2 tones, from F''' to A''. Many individuals vary only 2 1/2 tones or 3 tones in the entire song. Though the song is comparatively simple, it is always pleasing, perhaps largely because of the soft tone and lack of very high-pitched notes prevent any shrillness.
"Bluebirds sing from March to July or August. The song does not always begin when the first migrants arrive. In 8 out of 29 years of observation in Connecticut, bluebirds were singing when first noted in arrival. In other years several days elapsed before song began. The average arrival is March 10, but the average first song is March 18. The earliest date of beginning of song is March 3, 1923, and the latest April 2, 1940. Since the bluebird is never very common in the North and has periodical periods of scarcity, I often hear very little song in summer. In only eight years have I heard the song in July or August. In these years the average date of the last song is July 26, the earliest July 11, 1926, and the latest August 11, 1932.
"According to my observations, the male bluebird sings abundantly during courtship and nest-building, following the female about as she makes trips to and from the nest for nesting material. But as soon as incubation begins, the song ceases abruptly and is not renewed until the young of that brood have left the care of the parents and it is time to start a new nesting.
"The call notes of the bluebird are fully as musical as the song. These notes may be 2- or 3-syllabled, oola, aloo, oolaloo, or aloola. They may be heard frequently in the fall migration, as flocks of the birds fly over in October and November. The alarm note, given when the young are just out of the nest, is the only harsh sound I have heard from this bird; it sounds like chat or is often doubled to chatat."
Mr. DuBois writes the fall note as juuit or Juliet, which seems to be a good rendering of it. I have heard this plaintive fall note early in spring, before the real song season begins. To John Burroughs (1871) the bluebird seems to say "Bermuda! Bermuda! Bermuda!" The song has often been expressed in other syllables such as turwy, cherwee, cherey-lew, or tura-lee, in soft, liquid, musical tones. W. E. Saunders (1887) once heard, and saw clearly, a bluebird imitating the kay-kaynote of the blue jay; he "found that after the bluebird had warbled from four to seven times, the next warble would be prefaced with the Jay note."
The bluebird has about the lowest-pitched voice of any of the passerine birds; the crow's voice is decidedly lower, and that of the Baltimore oriole is slightly lower on the average but has a higher range. According to Albert R. Brand (1938) the bluebird's voice has an average mean frequency of 2,550, a maximum of 3,100, and a minimum for the lowest note of 2,200 vibrations per second.
Enemies.--Bluebirds seem to have no human enemies; everybody loves the gentle birds and appreciates that they are very useful and harmless tenants in our orchards and about our farms and gardens. But they have plenty of natural enemies to contend with. Cats readily climb to many of their most accessible nests and can reach in and pull out the young or the incubating parent; snakes climb into some cavities and destroy the eggs; red squirrels and blue jays invade the nests and eat the eggs or young; and house wrens often puncture the eggs, so as to appropriate the nest. Mrs. Laskey (1942) reports for that season: "A total of 174 sets, 774 eggs, were laid. From this large number only 261 young, 33.7 percent, left the nest box safely. Predation was heavy, 81 nests being entirely unsuccessful. Among these, 18 mother birds and 46 nestlings are known to have been destroyed by cats and 55 eggs failed to hatch through the loss of the incubating females. A boy robbed 11 nests of eggs; 42 were rifled of their contents by snakes. A 54 inch specimen collected in one of the boxes last year after eating the young was identified by Dr. Jesse M. Shaver, Peabody College, as a Southern Pilot snake (Elaphe obsoleta obsoleta)."
Dr. Herbert Friedmann (1929) says that the bluebird is "a very uncommon victim" of the cowbird, and cites about 15 records. Later (1934) he reports seven additional records and states: "Although the bluebird is still to be considered a rather infrequent victim of the cowbird, it is by far the most often parasitized of hole-nesting birds." Mr. DuBois writes to me that he found five bluebirds' eggs and two cowbirds' eggs in a box in his yard; all the eggs hatched, except one bluebird's egg, which was found on the ground, punctured; the other six eggs hatched, but the sun was very hot and most of the young perished from the heat; one cowbird and possibly one bluebird survived, though he could not find the latter.
Dr. Musselman (1942) once found in one of his boxes a filthy nest with four half-grown bluebirds cuddled in the bottom; and above them was a two-thirds-grown starling sitting complacently on the smaller birds; "the droppings of the larger bird had soiled and in one case almost covered the head of one of the tiny birds below; one eye was entirely covered and there was a stench which is unusual about such a nest." He destroyed the young starling, washed the young bluebirds, rebuilt a clean nest and returned the young bluebirds to it; the mother bluebird accepted the change and raised her young successfully. "In the many years that I have carried on my Bluebird experiment, I have never before found a Starling roosting in or employing one of my boxes for a nest site. In fact, only upon three or four occasions have I found Cowbird eggs in the normal nest. Only when somebody has removed the top of a box thus allowing an approach of the female Cowbird through the aperture above has there been molestation on the part of the Cowbirds."
Competition for nesting sites is one of the bluebird's greatest troubles. House wrens have always been aggressive competitors, but the bluebirds have generally been able to resist them and sometimes to evict them. Edward R. Ford has sent me the following note: "When young bluebirds left the 6 by 7 by 7 inch nesting box, June 20, I cleaned it out at once. By noon of the same day, house wrens took possession and began filling it with twigs. A few days later I noticed that bluebirds were still about the box, and when I looked into it on June 29 it held three bluebird's eggs. When the second brood had flown, August 2, an investigation showed that the bluebirds had assumed ownership before the wrens had completed the usual true nest in the twig mass and had made a scanty one of their own with a few dry grass stems."
When the English sparrows came the bluebirds had to face a determined competition; often the bluebirds were more than a match for the sparrows; but when the sparrows came in groups or droves they were too much for the bluebirds to resist; fortunately, the sparrow population is not so formidable as it once was, since its numbers have declined some. But the introduction of the starling gave the bluebirds another setback; these large, powerful birds can easily drive out the bluebirds and occupy any of the larger cavities; many old apple orchards that formerly housed bluebirds are now preempted by starlings. Bluebirds are safe from these intruders, however, in many of the properly constructed bird boxes; if the entrance hole is not over 1 1/2 inches in diameter the starling cannot enter; but a 1 3/4-inch hole might allow the starling to use the box.
Bluebirds are generally able to contend with tree swallows, to drive them out or to defend their homes against them. A housing feud between these two species is mentioned above, under "Behavior." Flying squirrels, deer mice, and even bumble bees have been known to appropriate suitable cavities for bluebirds.
Harold S. Peters (1936) lists two species of lice, one fly, and two species of mites as external parasites of the eastern bluebird. Doubtless there are other forms of vermin that infest the nests.
I have left until last the bluebirds' most formidable enemy, Jack Frost, the agency that has destroyed more of them than all other enemies put together; countless thousands have succumbed to extreme cold, snowstorms, and cold, ice-forming rainstorms. Bluebirds seem to be very vulnerable to these elements in winter and even in spring. The most notable of these catastrophes occurred during the winter of 1894-95, the season of the "big freeze" in the southern states. Amos W. Butler (1898) describes the event as follows:
The weather was warm until after Christmas. December 27 and 28 it became quite cold in this latitude [Indiana]. The Bluebirds were forced farther southward beyond the limits of the severe weather. There it remained warm until late in January. On the 24th of that month the temperature as far south as South Carolina remained near the zero mark. It turned warmer that night and the next day, January 25, the weather was bright and clear. The day following was Friday. It rained, then snowed; the wind came down from the northwest with great velocity and the temperature fell rapidly. Everything was ice-bound or snow-bound to the Gulf of Mexico. Then followed weeks of unusual severity. By the end of the severe weather in April, it is said, but few Robins or Bluebirds could be found. The destruction of bird life must have been enormous. The Bluebirds seem to have been almost exterminated. Few, indeed, returned to their breeding grounds in the north and from many localities none were reported in the spring of 1895.
Bluebirds began to increase slowly during the next few years, but it was five or ten years later before they seemed to have reached normal numbers. A lesser reduction in their numbers in the East occurred as a result of the very cold winter of 1911-12 in the southeastern states, but this was more local in its effect, and the birds soon recovered from it. Dr. Musselman (1939) writes:
In the seven years that I have been banding and studying Bluebirds through the use of bird boxes, we have had three severe freezes in April after the majority of the Bluebirds had laid their full quota of eggs. Nearly always I found complements of frozen eggs deserted by the mother. Later, a second grass nest was built directly over the old eggs, then the new mother would begin her nesting activities. Seldom did the original mother return to her old nest. The unfortunate feature about such a catastrophe is not alone the destruction of fifteen hundred to two thousand eggs, but it is the fact that the nesting period is advanced by about two weeks. This means that these Bluebird boxes which are very much in demand by several types of birds have eggs in them at the time the House Wren (Troglodytes aedon) returns. The number of pierced eggs has been correspondingly large on the years of such freeze. During normal years the baby Bluebirds are in the nest at the time of the wrens' return. Generally they are not molested. On normal years the nesting is so timed that when the first batch of young Bluebirds desert the nest, the House Wrens have already established themselves elsewhere. When the Bluebirds return later for the second nesting, there is little danger that piercing of the second complement of eggs will take place.
In addition to the frozen and punctured eggs, he found on several occasions the frozen bodies of the incubating birds where they had died on their nests; and once two birds were found frozen to death in a single box.
Fall.--Dr. Winsor M. Tyler has sent me the following sketch: "Bluebirds are all along the roadsides this morning--a windless, warm, October day. They are gathered socially in companies of half a dozen or more and keep near together like a big family, one bird following another when it flies. They are quietly musical as they flit about, giving the gentle whit call, the softer chatter, the velvety turwy, and sometimes a phrase of song. It is easy to imagine that the bluebird's song was evolved from a repetition of the whit note, perhaps by way of the turwy; a slight change in the tone of voice making it mellower, louder, and sweeter, lengthening the notes a little, and there is the song.
"The birds perch on dead branches, wires, or fence rails, scanning the ground as from observation posts, sitting upright with the tail straight down; they explore holes in the apple trees, peering in, sometimes entering the cavities, calling to one another; they drop to the grass or to the hard, surfaced roadway where they catch up something with a deft peck. The bluebird's shadow at this season, the myrtle warblers, come down to the road, too, and act in the same way.
"In flight bluebirds are very charming at this time of year; a leisurely flip of the wing carries them along silently with just enough momentum to keep them afloat in the air, and they often sail for a long way, drifting along with open wings. In contrast to the goldfinches and purple finches they fly only a short distance before alighting again. We shall see few more bluebirds before winter comes. This little company is already on its way south, yet they seem in no hurry to leave New England. How leisurely the bluebirds are as they flit about in fall!"
Only in the northern part of its summer range can the fall migration be satisfactorily traced, but there it is sometimes quite conspicuous. Robie W. Tufts writes to me that bluebirds are uncommon in Nova Scotia, but during October 1937 a flock containing "some hundreds" was observed in Annapolis County. "These were seen at the peak of their abundance for only a short time, but bluebirds were seen more or less constantly for a few days after the main flight had passed. Considering the relative scarcity of these birds in Nova Scotia, the origin of same is a mystery to me."
In Massachusetts we usually see them passing through in October and November. Out in the open country on clear days with a northwest wind, we often hear their sad farewell notes drifting down around us from all directions; and, looking up into the blue sky, we see large numbers flying over, high in the air, widely scattered or in small detached flocks, and all floating along in a generally southward direction; we know that they are leaving us and we are sorry to see them go. They sometimes turn up in unexpected places; on November 1, 1915, a flock of eight appeared at our shooting club among the sand dunes of Monomoy Island; the next day they were joined by 10 more; these were two clear, warm days, but the following day it blew a gale from the northwest, with heavy clouds and some rain; the bluebirds had departed.
Edwin A. Mason writes to me from Groton, Mass., that on November 3, 1942, at 8:00 a.m., "it was raining, with a fairly strong wind blowing from the NNW. Birds from the tops of tall bare willows caught my ear. There, throughout the tips of the tree's branches, was a flock of bluebirds. They were moving occasionally from twig to twig, constantly talking back and forth. Very soon the major part of the flock took to the air. This made it possible to count them. The surprisingly large number of 28 were winging their way through the rain in a SSW direction, with the wind quartering them somewhat, but still substantially on their tail. Evidently the flock had paused to rest and despite the rain considered it a good time to continue on its migration. Three birds hesitated to join the flock, one of them starting out after it only to return. These three probably tired birds remained, calling back and forth, as the main body of their erstwhile traveling companions went winging away southward through the dull leaden sky, their voices and shapes gradually diminishing as the vastness of the murky sky enveloped them."
The flock observed by Mr. Mason was not "surprisingly large," for the birds are often seen in larger flocks, sometimes as many as a hundred, though usually more or less scattered. Late in summer and early in fall mixed flocks of old and young desert their breeding resorts and wander about the open country and woodland, often associated with similar flocks of roving robins, all of which are much wilder and more restless than they are about our grounds in nesting time. Bagg and Eliot (1937) state that, in the Connecticut Valley in Massachusetts, "in October, transient Bluebirds are abundant, and natives come back as if to say good-bye to their homes, and sometimes carry nesting material into their boxes, in that Indian summer of the procreative instincts that many birds evince on warm October days."
Referring to the Buckeye Lake region in Ohio, Milton B. Trautman (1940) writes: "The first southbound migrants were noted during the first half of September, and until the end of the month a rather gradual, daily increase in numbers was observed. The migration reached its peak in October, when the bird was as numerous as in spring. In autumn its lisping note, uttered from overhead or from a fence post or tree, was one of the most pleasing and familiar of all fall bird calls. The Eastern Bluebird was very conspicuous during the calm, warm 'Indian summer' days of late October--such weather was called 'bluebird weather' by local sportsmen."
At Point Pelee, Ontario, the migration is often conspicuous; on October 29, 1905, according to Taverner and Swales (1908), bluebirds were there in numbers. "Here numbers were feeding on the bare sand with the Prairie Horned Larks. It was in the waste clearings beyond Gardner's place, however, that the greatest numbers were found. Here they were in flocks almost as dense as blackbirds. When flushed from the ground they generally flew to some of the numerous clumps of bushes growing here and there in the open and, when they lit and were viewed from a little distance, they were in sufficient numbers to give the whole bush a decidedly blueish cast."
Winter.--A few bluebirds spend the winter in southern New England, especially in mild seasons and more commonly near the seacoast, feeding on bayberries with a few wintering myrtle warblers or on the seeds of sumacs. They take shelter in the dense growths of red cedars, which protect them from the cold winds and furnish some berries for food. They roost in hollow trees or in bird boxes, sometimes several together. Mr. Forbush (1929) cites William C. Wheeler, of Waltham, Mass., as having twice seen one go to roost in an old robin's nest. Dr. Harold B. Wood writes to me that bluebirds were common all through the winter of 1913-14 at Slocum, R.I., which is five miles west of Narragansett Bay in the central part of the state.
Bluebirds sometimes winter in the more northern parts of the midwestern states and even in southern Ontario. There are winter records for Point Pelee. And E. M. S. Dale says in his notes from London, Ontario: "Although the bluebird is one of our earliest spring migrants, it was not until December 27, 1937, that we found any here in winter. On that date we found four birds about a bit of marshy ground, where some springs had kept the snow melted and gave them a chance to obtain food. The ground was covered with snow; in fact, we were taking a hike on skis and snowshoes when we found them. The temperature had been down to 8o below zero a few nights before. They were still there on January 1 when we went out to begin our New Year's list."
From the Carolinas southward bluebirds are present all through the year, but they are probably not the same individuals, the local breeding birds having moved southward to be replaced by others driven down from the north. M. P. Skinner (1928) says: "This seems all the more probable because during cold spells I found Bluebirds gathered in large flocks of as many as seventy birds in most unusual places. They did not seem to be familiar with the country and its supplies of food and water. But with warmer weather these large flocks of strangers disappeared and the familiar birds were found again in the usual small groups."
In their winter resorts they are found in the more open woods, such as the flat pinewoods of Florida, seeking the denser growths only for shelter and spending most of their time for food in the more open places, such as cotton, corn, and sugarcane fields. In such places they are often associated with myrtle, pine, and the palm warblers.
A. L. Pickens tells me that "the sheltered nooks selected by individuals are interesting. A flock, I once observed, selected the cracks between the logs of a cabin in which cotton that had not been ginned was stored. Packed thus against the logs the cotton afforded a heat retainer, while the upper log gave shelter and the lower footing. One bird I saw took possession of an old summer-tanager nest for a winter dormitory."
M. G. Vaiden tells in his notes of a winter disaster not mentioned above: "For some reason, probably the terrific winter of 1906 when sleet was 4 to 6 inches deep over a great part of central Mississippi with a complete freeze-up of the ground for some 4 to 6 inches deep, when some trees were frozen and the trunks burst open, the bluebirds of this area, the normal breeding population, were frozen to death or died of hunger and thirst, and the nesting of the bluebird in the hill section certainly fell away considerably." He believes that the breeding birds of that area remain and mingle with the migrants from the north, rather than migrating farther south.
When all the vicissitudes with which bluebirds have to contend
are considered, it is not strange that there seem to be no records
of great longevity. Mrs. Laskey says in her notes: "So far
none of my banded nestlings have been found after three years. The
high rate of mortality through predation is doubtless the main
factor in this prevailing short life span. The oldest bluebird of
record in the Parks group is an adult female, banded May 1938 and
nesting there each year. Her latest capture was in April 1942,
when she was at least four years old. Another female, banded at my
home as an adult in April 1936, was retrapped each year until
November 4, 1939, when she was at least in her fifth year of
Eastern Bluebird* Sialia sialis
*Original Source: Bent, Arthur Cleveland. 1949. Smithsonian Institution United States National Museum Bulletin 196: 233-260. United States Government Printing Office