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LIFE HISTORY

Published by the Smithsonian Institution between the 1920s and the 1950s, the Bent life history series of monographs provide an often colorful description of the birds of North America. Arthur Cleveland Bent was the lead author for the series. The Bent series is a great resource and often includes quotes from early American Ornithologists, including Audubon, Townsend, Wilson, Sutton and many others.

Bent Life History for the Blue-headed Vireo - the common name and sub-species reflect the nomenclature in use at the time the description was written.

 

BLUE-HEADED VIREO
VIREO SOLITARIUS SOLITARIUS (Wilson)

HABITS


The yellow-throated vireo may be more brilliantly colored, with its bright yellow throat, but, to my mind, the subject of this sketch is the handsomest of the vireos. His gray-blue head is accented by a pair of pure-white spectacles, eye rings, and loral stripes; in marked contrast are his olive-green back, his pure-white throat and breast, and his yellow sides. The soft color tones combine to make a most charming picture of pleasing loveliness. He appears to be a well groomed aristocrat among birds. In addition, his song is delight-. fully rich and varied, to which we always stop and listen. And his gentle, trustful manners, as we try to stroke him on the nest, have endeared him to all who know him. He is a lovely and a lovable bird.

I had seen the blue-headed vireo as a migrant in southeastern Massachusetts, but it was some years before I came to know it as a breeding bird; this was mainly because I did not know where to look for it, until one of my rivals in egg collecting reported finding a nest in a grove of white pines (Pinus strobus). Since then we have learned to look for it in the white-pine woods, with which this section of the State is well supplied. It is a forest-loving bird, and we practically never find it breeding anywhere but in woods where these pines or hemlocks make solid stands or at least predominate; often, however, such woods contain scattering growths of gray birches, wild apple trees, or sapling hardwoods of various kinds, in which the vireos like to build their nests.

It may be purely accidental,but it is an interesting fact that we have often found the blue-headed vireo nesting in a tract of pines occupied by a pair of breeding Cooper's hawks; I find six such cases recorded in my notes, and once the vireo's nest was within 50 feet of the occupied hawk's nest; but we have never found this vireo nesting rn similar woods where sharp-shinned hawks were breeding. We never saw anything to indicate that the Cooper's hawks ever harmed the vireos, or their young, but it might have been different with the sharpshins! Perhaps the vireos have learned to trust the larger Accipiters. They evidently prefer the same type of woodland as the hawks; hence this apparent community of interest. I once found a pair of blue-headed vireos building a nest in a similar tract of pine woods where a pair of barred owls had a nest.

In the Allegany State Park, New York, Aretas A. Saunders (1938) says that "they inhabit both the Maple-Beech-Hemlock forest and the areas modified for camping, and seem to be rather more common on the campaign areas or about their edges, apparently liking the edge of the open area and having no fear of man's presence. "Where much undergrowth is removed, however, they do not occur, as there are then no nesting sites near the ground, and it is my experience that the nest is rarely placed very high."

Leonard Wing (1939) says that, in the Upper Peninsula of Michigan, "the Blue-headed Vireo lives in the heavier growth of Jack Pine."

Spring: The spring migration of the blue-headed vireo seems to be quite prolonged. Alexander F. Skutch tells me that few are seen in Central America after April 19, only one being seen after that on the 28th. Yet the species arrives in Massachusetts around the middle of that month, Forbush's (1929) earliest date being April 11. We look for them in numbers before the end of April, in the vanguard of the migrating hosts of small birds, along with the black-throated green and yellow warblers, the towhee, catbird, and brown thrasher, but at least a week ahead of the other vireos.

Territory: Mr. Saunders (1938) writes:

One difference in habit between this bird and the red-eyed vlreo Is that of wandering about when singing, apparently with no fixed singing tree. This habit makes it difficult to determine territory and to get a definite count of birds. This would be more difficult If it were not for Individual differences In songs. This wandering habit keeps singing birds moving about over a considerable area, and I have known them to sing now and then in the same tree In which a red-eyed vireo sings regularly. In such cases there is no jealousy or animosity shown on the part of either species. Such observations leave me holding some doubts about the territory theory, both in vireos and some other birds. It would seem that the two species should be rivals for food, nest sites and nesting materials. Yet their territories, if they have such, frequently overlap with no hostility between them, at least in late summer. If there Is some sort of territory in this species, it seems to be larger than that of the red-eyed vlreo. Singing males are not very close together, and nests not near each other.

Courtship: Dr. Charles W. Townsend (1920) says: "Twice I have been favored with a sight of the courtship performance. The male puffs out his yellow flank feathers very conspicuously and bobs and bows to the female, very slim in contrast, and sings repeatedly meanwhile with many variations to his song."

In a patch of swampy woods back of a pine grove, I once watched a pair of blue-headed vireos for a considerable length of time and followed them about, as they seemed to be making love to each other; the female was in the lead, but the male was not far behind her, displaying his charms. He sang his loud, rich, two-note song, so much like the song of the yellow-throated vireo in tone, at regular intervals. But he varied it occasionally, especially when near his mate, with a series of sweet, warbling notes in a subdued tone, cher 'wee, aweeck, 8Weeeh, sweech, to which she generally replied in a similar strain, as they came together for an interchange of caresses. Near there I found their new nest.

Nesting: AIl the nests of the blue-headed vireo, at least a dozen, that my companions and I have found in eastern Massachusetts have been in, or on the borders of, white-pine woods, seldom in clear, thick stands of Pi'nus atro1~us, but more often in mixed woods of pines, hemlocks, oaks, and other deciduous trees where the pines or hemlocks predominated. I find only two exceptions to this rule in the literature. C. W. and J. H. Bowles (1892), of Ponkapog, Mass., report a nest that "was about eight feet from the ground on the lowest branch of a thirty-foot live oak. This was in a grove of other oaks of the same size. This, we think, is an exceptional case, as all our other nests were built in coniferous trees." And Dr. T. M. Brewer (Baird, Brewer, and Ridgway, 1874) says: "In the summer of 1870 a pair built their nest in a dwarf pear-tree, within a few rods of my house."

F. H. Kennard reports, in his field notes, a nest 12 feet from the ground in a small pine, and Owen Durfee's notes record a nest that was 26 feet up and 10 feet out from the trunk of a large pine. He and I once found a nest, ~½ feet from the ground, in a white-cedar sapling under a large hemlock in swampy mixed woods. Mr. Kennard's notes mention one that was only 4 feet up in a small hemlock under some large pines. All our other local nests were in saplings of deciduous trees, mostly oaks, but also gray birch, beech, hickory, and walnut. The lowest was 31/2 feet up in an oak sapling and the highest 20 feet in a slender oak.

Farther north the nests are generally built in coniferous trees, Mr. Kennard's notes mention a nest at Averill, Vt., that was about 6 feet up in a slim spruce on the bank between a trail and a stream, and one at Duck Lake, Maine, in a spruce. Robie XV. Tufts writes to me from Nova Scotia: "With but one exception, all nests of this species have been found in coniferous trees of various kinds. The single exception was a nest found in a wild apple tree. Conifers were close by."

Dr. Wing (1939) writes: "June 26, 1932, I found a nest under construction at the Lake Superior State Forest, twenty-six miles northwest of Newberry, Michigan. The birds had chosen a thirty-five-foot Jack Pine tree for attaching the pensile nest, which was in the fork of a horizontal branch twenty feet from the ground and three feet from the trunk of the tree. Lichens and shreds of birch bark composed the framework of the nest, and thin dry grasses served for lining.

Mr. Saunders (1938) says of the nests of the blue-headed viree in the Allegany State Park, New York:

They range from four to 30 feet from the ground; in fact, with the exception of one nest In an area of mature timber on Red House creek, all nests I have seen have been ten feet or less from the ground. They are placed In beech, sugar maple, yellow birch and horubeam trees and probably other species, but these species are most abundant in the forest and therefore most commonly used. I think the bird does not have any special preference for one species over another.

The nests are Indistinguishable from those of other vireos. Under natural conditions they are composed of bark, leaves, bits of moss and some grasses, strips of yellow birch bark, in this region, being a conspicuous material. About camps they frequently use paper, and are evidently just as fond of newspaper as Is the red-eyed vireo. Tissue paper, cellophane and a piece of chewing gum wrapper have all been found in the nests. One nest was gaudy with strips of colored tissue paper that had been supplied to the birds by a student at the school. One nest back on the mountainside that had no such artificial materials, had three porcupine quills woven into its rim.

C. M. Jones (1887), of Eastford, Conn., found three nests in laurel bushes, between 8 and 7 feet above the ground, and one suspended near the end of a long horizontal branch of a hemlock tree, about 5 feet from the ground. Most of the nests reported by others have been almost, or quite, within reach from the ground.

The hanging, basketlike nests of the blue-headed virco, like those of other vireos, are suspended by their upper rims, often none too securely, from the supporting twigs. The nest may be at the forked end of a long, slender branch of a tree, between the prongs of a forked twig, or between two twigs projecting side by side from the upright stem of a sapling; and it is almost always close to where the prongs start to fork, or close to the stem of an upright.

The nests that I have seen vary considerably in size, neatness, and kind of materials used in their composition. Most of the materials mentioned in the above descriptions are likely to be found in one or another of the nests. Brief descriptions of three nests before me will illustrate some of the variations. One nest, built early in the season, is not beautiful but is one of warmest and coziest cradles for an early brood of vireos that I have seen; the body of the nest is made mainly of strips of inner bark of grapevine, various soft plant fibers, many fine rootlets, pieces of thread and fine grasses, mixed with lichens, bits of mosses, bunches of rabbit hair, bits of cotton and soft feathers, including a large downy feather of a great horned owl; it is neatly lined with some peculiar hairlike filaments, light yellow and red at the base, which I think are the roots or stems of club mosses.; on this lining are a few small downy feathers, a little cow hair, ai~d a little rabbit fur.

The second might be considered an average nest, built in July and very insecurely attached to a forked twig of a swamp white oak; it is prettily made of strips of inner bark of various kinds, bits of lichens, and mosses and decorated externally with many pieces of paper from the nests of wasps or hornets and a few spider nests; it is profusely lined with fine needles of the white pine. It measures about 3½ by 3 inches in external diameter and about 21/4 inches in external depth; the inner cavity is about 1½ inches in (lepth and about 2 by 21/4 inches across the top, with very little overhang.

The third came to me from Lancaster, N. H., taken by Fred B. Spaulding. It is the largest, most compactly built, and handsomest nest that I have seen of this species, perhaps more typical of northern nests than of those with which I am familiar. It is securely attached to two diverging twigs close to the upright stem of a sapling with a quantity of usnea and fine strips of outer bark of the yellow birch.

The bulk of the nest is made up largely of various lichens and mosses, mixed with bits of small dry leaves, bits of fine string, and spider nests, all apparently firmly interwoven with narrow strips of the outer bark of the yellow birch, with which the exterior of the nest is profusely decorated. It is smoothly lined with very fine grass tops and a few hairlike rootlets. Externally it measures about 3 by 3½ inches in diameter and ~½ inches in depth; internally it measures about 2 by 13A in diameter and about 1½ inches in depth, the walls being very firm and thick. The above measurements do not include the extent to which some of the loose streamers of the birch bark hang below and around the nest.

I have twice watched blue-headed vireos building their nests. Both of the pair help in this work, though the female seems to do most of it and to be the dominant influence, the male's part consisting mainly of bringing material. At the beginning of the nest a few hanging loops of soft fibers are attached at both ends to the supporting twigs; as these increase and the bag is formed, the ends are securely bound to the twigs by strips of usnea or fine shreds of inner grapevine hark, forming the rim of the nest; some spider web may be used for this purpose, but it does not seem to be much in evidence in the nests that I have seen; apparently the bluehead docs not use so much of it as do other vireos. The rest of the material is worked in between the hang ing loops, and finally the lining is added and the interior is shaped by the turning of the bird's body in it. The birds are very apt to desert an unfinished nest, if watched, as happened in the two cases that I observed.

Eggs: The blue-headed vireo lays three to five eggs in a set, usually four. These are usually ovate in shape, but some are quite pointed.

The ground color varies from pure white to creamy white. They are rather sparingly spotted or dotted, mostly near the large end, with light brown, dark brown, reddish brown, or blackish. The measurements of 50 eggs average 19.5 by 14.4 millimeters; the eggs showing the four extremes measure 21.8 by 14.7, 19.6 by 15.3, 17.0 by 14.1, and 18.1 by 13.4 millimeters.

lncubation: F. L. Burns (1915) says that the period of incubation is 10 to 11 days, but this must be based on insufficient information, for the other vireos require a somewhat longer time; no further data on the subject seem available. Mr. Saunders (1938) remarks that his experience "indicates that the period of incubation is at least 11 days long, but, up to date there has been no opportunity to determine its length definitely."

Both parents share the duties of incubation and are devoted to the care of the young. They change places on the nest at regular intervals regardless of the near presence of human observers. Sometimes when we drive the female from the nest the male will take her place within a few feet of us. They are usually very close sitters and often must be lifted, off the nest if we want to examine the eggs. Mr. Saunders (1938) says: "Changing places is accompanied by a call by which the incubating bird notifies its mate. The mate answers with the same call, and comes immediately. The call is a soft, rather, low-pitched trill, running downward in pitch at the end, like 'tiprrrrrr.' This call is interpolated in the song by some individuals."

The male sings regularly while incubating, and probably the female does to some extent; Mr. Saunders (1938) remarks: "It is impossible to distinguish sexes by plumage or by habits about the nest, and my observation that the female sings is based on observing two birds, both in song, one singing while incubating and the other answering from near-by trees."

Dr. Cornelius Weygandt (1907) writes:

The comradeship of the two during incubation had been very winning. As one sat upon the eggs the other would come flying swiftly to a dead limb above and then drop to the little branch from which the nest swung, landing not a foot away from it. Here the incoming bird would mew, ever so caressingly, and the bird on the nest would answer In the same low tone. Sometimes the interchange of greetings would be followed by interchange of positions, the sitting bird first unsettling Itself gently from the eggs and then flitting off to alight beside Its mate. The incomer would lift itself into the nest as deftly and then after a few more mutual mews the relieved bIrd would be off to the oak-tops. Once the sitting bird, this time I suppose the male, sang while brooding on the nest when the other returned.

Young: Mr. Saunders (1938) says:

Singing takes place all through the Incubation and while the young are still very small, but It gradually ceases as the young grow larger, and is heard not at all after they are five or six days old, and Is only resumed after they have been out of the nest nearly a week and are able to shift for themselves. * * When feeding young, the adults are rather more concerned than they are when incubating, perhaps not for themselves, but they do not entirely trust a man near the young. An alarm call, used at such a time, is a protesting "shfl shfl shti shfl shfl." Even this note is gentle when compared with the alarm notes of most birds.

Young are fed by both birds, chiefly on insects, of which span-worms are the most conspicuous and easily identified. One student observed a dragon fly fed to the young, wings and all. From her description it was apparently Aeschna ambrose, a fairly large species. It is not probable that a vireo could catch a fully matured adult dragon fly, but in the morning, whea the insects have just emerged from the nymph stage, their wings are soft and they are incapable of flight, and easily caught.

When the young are out of the nest, parents are still busy feeding them for a few days. At such times, if the young are near the ground, the parents still show little fear of man, and come to feed them in front of groups of people and camera lenses.

The very early and very late dates at which eggs have been found suggest that two broods are sometimes raised in a season, as seems to be the case with the mountain vireo.

Plumages: .The juvenal plumage of the blue-headed vireo is much like that of the adult in pattern, but the general coloration is duller. Dr. Dwight (1900) describes it, in part, as "above, drab, tinged with green, pileum and auriculars drab-gray. * * * Below, pure white, tinged on flanks and crissum with primrose-yellow. Obscure superciliary stripe, loral and orbital regions white; a dusky anteorbital streak."

The first winter plumage is acquired by a partial postjuvenal molt in August and September, which involves the contour plumage and the wing coverts but not the rest of the wings nor the tail. In this plumage the young bird is practically indistinguishable from the adult, though the head and back are more or less tinged with brownish and the white of the underparts is less pure. Both old and young birds usually, though perhaps not always, have a partial and irregular prenuptial molt in March and April, at which a few or more feathers are renewed on the head, back, throat, and breast.

The sexes are practically alike in all plumages, though the coloration of the female is usually duller.

Food: The Biological Survey had 306 well-filled stomachs of the blue-beaded vireos and 23 other stomachs only partially filled, on which Dr. Edward A. Chapin (1925) based his report on the food of this species. The animal matter, 96.32 percent of the entire food, consisted almost entirely of insects, the few spiders included amounting to 2.63 percent and the snails 0.25 percent. Lepidoptera, in all stage; were the largest items, averaging 38.8 percent for the whole year; caterpillars were eaten in greatest numbers in March (41.56 percent) and in September (40.39 percent) ; the greatest consumption of adult moths caine in July (18.38 percent). Ilemiptera, true bugs, formed the second largest item, averaging 20.13 percent for the year, stink bugs (Pentatomidac) predominating. Dr. Chapin writes:

During the winter months hibernating pentatomids constitute one of the most important sources of food for the blue-headed vireos, as shown by the November and January percentages of 48.7 and 29.02, respectively. * * * Considering the enormous numbers of beetles available, it is somewhat surprising that not more are eaten. The blue-heads manage to seek out enough, however, to make up 13.51 percent of their entire diet. Of this, the ladybird beetles make up 4.88 percent, or more than a third. It is certain that there are not a third as many ladybird beetles as all other beetles combined; and thus it must be considered that the blue-headed vireos, like the warbling, either find these brilliantly colored forms in abundance in their environment or else make special search for them, a most undesirable habit economically. Roughly, a second third of the total bulk is composed of the metallic wood borers, the longicoras, and the click beetles. The remaining portion Includes, among others, the weevils, which comprise 1.8 percent of the food.

The average of Hymenoptera for the year was 6.86 percent, and of flies, Diptera, 4.29 percent. Other insects eaten include stoneflies, dragonflies, grasshoppers, crickets, and locusts (6.56 percent for the year).

The small percentage of vegetable food was mostly "in the form of fleshy fruits, such as wild grape, dogwood, viburnum, and wax myrtle. No cultivated fruit was identified, and it is practically certain that none is eaten." The average for the year was 3.68 percent, but in January it formed nearly a quarter of the total food, 24.37 percent.

Aaron C. Bagg (Bagg and Eliot, 1937) says: "The height of the Blue-head's migration coincides with the emergence of tent-caterpillars. At Holyoke on May 10, 1926, I watched one of these Vireoe take most of the young caterpillars in one web, then fly to another and repeat the heavy meal."

Alexander F. Skutch writes to me: "Once in the highlands of Guatemala I saw a blue-headed vireo pick up a very long caterpillar, possibly an inch in length. At first the bird seemed puzzled to know what to do with it, and crossed to the other side of the tree with the larva dangling from its bill. Here he laid it along a twig, held it there with a foot, and took a few nibbles or tugs at it. Then he took it in his bill again, still nearly or quite intact, and swallowed it whole. The habit of using the foot for holding food, while it is torn apart with the bill, appears to be very imperfectly developed among the vireos, hut has attained a high degree of efficiency in the related families of shrikevireos (Vireolaniidae) and pepper-shrikes (Cyclarhidae)."

The blue-headed vireo lives mainly in the trees of the forest and obtains most of its food among the twigs and foliage, where it gleans quietly and thoroughly. But Ora W. Knight (1908) says: "I have also on several occasions seen one of these birds spring into the air after passing insects after the style of a Flycatcher, in fact this manner of feeding would seem to be more characteristic of this species than of any other Vireos with which I am acquainted."

Behavior: One of the chief characteristics of the blue-headed vireo is its tameness or fearlessness, or perhaps its confidence in man or its indifference to his presence. Its gentle demeanor when its nest is approached is in marked contrast to the aggressive tactics employed by some other vireos and by many other birds. There is seldom any scolding or great excitement and no attempt at attack, but a brave display of parental devotion. Many a bird-lover has enjoyed the thrill of stroking the incubating bird on its nest, or perhaps lifting it off without even being pecked in the attempt, and then seeing it settle down in the nest again with apparent confidence. It is a gentle little parent that soon wins our admiration and our affection. Perhaps it will even sing almost in our faces as it returns. With patience one may be persuaded to take food from our fingers when incubating or brooding. But individuals are not all alike; some will quickly leave the nest, if we come anywhere near it, and will not return to it while we are in the vicinity.

With all its tameness and tolerance of humans, the blue-headed vireo is not a sociable bird; it does not seek the company of man or the security of our home grounds; it is seldom seen in our yards and gardens or in the shade trees of village streets and city parks, except on migrations. It is rather a recluse of the woodlands, the solitudes of the forests, often well hidden in the foliage of the tree tops; we must seek it there in its shady retreats, if we would make its acquaintance. If we follow the lead of its rich song, we may see it sitting quietly on some outstanding branch near an opening or among the lower branches of a forest tree. It may remain in one spot for a long time or move about very deliberately while feeding, for it is far less active in its movements than the smaller vireos. Quiet dignity and an air of calm repose seem to dominate its behavior in the security of its woodland home.

Voice: Aretas A. Saunders contributes the following account of the music of this vireo: "The song of the blue-headed vireo is longcontinued, made up of phrases separated by short pauses. It is the highest in pitch of the common vireos of eastern United States, and of exceedingly sweet, clear quality. The phrases are delivered more rapidly than those of the yellow-throated vireo, but more slowly than those of the redeye. On the whole it is the most pleasing of the vireo songs.

"From a study of the records from 37 individuals, the pitch varies from Eb ' ' ' ' to B' ', two tones more than an octave. The rate of singing is about one phrase to a second, or a second and a half. The phrases themselves are delivered slowly, the slurred portions being long-drawn-out and strongly accented. Each individual uses 9 to 15 different phrases. These are delivered in a varied order, which avoids the monotonous repetition found in the yellow-throated vireo. Phrases are composed of two to six notes. Two-, three-, and four-note phrases are common, while five- and six-note ones are rather rare. The notes of the phrases are sometimes connected by slurring and sometimes by abrupt changes. In phrases of three or more notes both kinds of changes may occur in the same phrase. Such phrases are characteristic of the song, and a help in distinguishing it from other vireos. Such phrases may be written awee to, teeaytoay, taweetayo, etc.

"On the breeding range in midsummer, this bird sometimes runs all its phrases together, omitting the pauses, producing a warble of 15 or 20 notes, the song then suggesting that of the warbling vireo. This song is heard commonly in the spring migration in April, and occasionally in fall in October.

"On the breeding grounds the period of song lasts till about the third week in August. Then individuals cease singing for a time but revive the song in late August. Definite dates are difficult to determine, however, for some individuals revive the song before others have ceased the main period of singing. Where the species is common one or more birds are likely to he heard in song every day in the summer."

Francis H. Allen sends me the following notes: "I have heard from both birds of a pair, in June, a faint trumpetlike note uttered with the bill almost closed. Sometimes the note was sounded more emphatically with the bill opened a little more. It then had a more strident character. I have also heard the tin-trumpet note in August, sometimes with a variant in two syllables, tee-wek. The chatter of the blueheaded vireo resembles that of the yellow-throated but is not so loud.

"August 25, 1911: One feeding in trees in a drizzling rain uttered continually a rather harsh, nasal see-a, sometimes more distinctly dissyllable, like see-weep. Once he gave a succession of similar but short notes, like she-she-she-she-she. All the notes were more like the characteristic harsh note of the red-eye than the other call-notes I have heard from this species. This may have been a young bird (so far as could be seen in the rain and without a glass, it was not in full plumage), but it was well enough grown to take care of itself, and it was alone.

"One cold afternoon with spits of snow in early May, one of two blue-headed vireos in a hawthorn tree near my house sang 8otto voce with snatches of catbirdlike song, a trill, and, later, phrases of the regular song but faint."

The following note from Mr. Skutch is interesting: "Contrary to prevalent impression, the majority of North American birds that winter in Central America may be heard singing here. Most of them rarely sing until the time for their northward departure approaches, yet a few are tuneful even in the midst of the northern winter. Conspicuous among these are the yellow-throated and blue-headed vireos. With the possible exception of the orchard oriole, the blue-headed vireo is more songful while in Central America than any other of the winter visitants. Early in January 1935 they sang much among the shade trees of the Finca Mock, a great coffee plantation on the Pacific slope at the base of the Volcfin Atitl6.n. Their song resembled that of the red-eyed vireo but was sweeter and more varied and was interspersed with pleasing little warbles uttered in a low, soft voice. On the morning of January 13 all the blue-headed vireos I met, four in number, were singing persistently. Of course, a singing bird is far more likely to attract attention than one which is silent. At noon I came upon two that were singing against each other from neighboring trees. One repeated all the notes of the other, as if in rivalry. They continued this as long as I stopped to listen but did not lose their tempers and clash, as so often happens under these circumstances. It is rare to hear wintering birds sing in January and exceedingly rare to hear them sing so much as these vireos sang.

"In the highlands I often heard the blue-headed vireos sing during April. 'When two came together they sang against each other like the birds on the coffee plantation. l7iree, one said; and other repeated viTee. Then the first called vireo; and 'virec answered the second. They continued this pretty conversation for some minutes."

Many years ago, when my hearing was good, I wrote down my impression of the song as kweeeee, with a rising inflection as in the redeye's song, or kew~, with a falling inflection; sometimes there was only the kew, or a short kewe~1e; again there was a rich and full koy week, or per cheet. The first combination was the commonest, but it was often varied by the second.

The literature contains many references to the beautiful song of the blue-headed vireo, but there is little that need be added to the above accounts. William Brewster (1906) mentions an interesting bird that "had two songs, one perfectly characteristic of his own species, the other indistinguishable from that of the Yellow-throated Vireo. These songs were invariably kept distinct, the notes of one never being interpolated among those of the other; nor was the bird ever known to change from one to the other save after a well-marked interval of total silence." Dr. Thomas S. Roberts (1932) writes:

The song is to be distinguished from the Red-eye's especially by two curious characteristic phrases which are introduced at frequent intervals. These may be recalled by the syllables toheop-teu, the first note sharp and quick, the last prolonged; and the other couplet by the words johnny-cake, rapidly uttered. Later in the season, mid-July, the song may consist almost entirely of these notes and is then a curious medley of wheop-teu, wheo~-teu, johnny-cake, johnnycake, tcheop-teu, and so on, with now and then a few sweet, vireonine notes. At the end of the season, early in August, the wheo p-tea call is all that remains and this rings through the forest, an unmusical reminder of the beautiful song to be heard no more until the coming of another nuptial awakening.

Field marks: It is only in the brightest light that the head of the blue-headed vireo appears at all blue, and then it is only a bluish gray; in shadow, or at a distance, it appears a dark slate-color. But the pure white eye ring and the white stripe in front of the eye, the "spectacles," are conspicuous at considerable distance. On the nest the gleaming white throat, in sharp contrast with the dark head markings, shows plainly above the rim of the nest. The two white wing bars, which the red-eyed vireo lacks, the pure white breast, and the yellow sides are good field marks.

Enemies: Undoubtedly some eggs and young are destroyed by predators, such as blue jays, crows, chipmunks, squirrels, and perhaps snakes, as many rifled nests have been found. Based on my experience, mentioned above, Cooper's hawks do not molest them even when nesting nearby; and Mr. Forbush (1929) says that the vireos also nest in the same woods with goshawks and red-tailed and sharpshinned hawks.

The blue-headed vireo is a common victim of the cowbird; if the cowbird's egg is laid before the vireo has laid any of her own, the vireo may cover it up and lay her eggs in the upper story; Dr. Friedmann (1929) says that the bluehead does this more often than the other vireos; but, after any of her own eggs are laid, she will not cover them. Unless the alien eggs are removed, the poor vireos will probably raise only young cowbirds.

Harold S. Peters (1936), in his list of externa.l parasites, mentions enly one tick (flaemaphysalis leporis-palustris Packard) found on this vireo.

Winter: Arthur T. Wayne (1910) says that "this vireo winters abundantly in the great swamps which are in close proximity to our [South Carolina] coast. That it is a common bird in the months of December, January, and February there is no question, for I have often seen and counted as many as ten individuals in the course of a few hours. On mild days in winter the birds sing with some vigor, but it is not until March that the full volume of song is heard."

Arthur H. Howell (1932) says that, in Florida "in winter it is often found in low, swampy thickets." Dickey and van Rossem (1938) say of the blue-headed vireo in El Salvador: "The center of abundance of this very common winter visitant was along the upper edge of the Arid Lower Tropical Zone, in other words in the coffee districts at about 3,500 altitude. In numbers it compared favorably with the warbling and Philadelphia vireos, but of course was much more in evidence. The smaller species are ordinarily silent or at least do not sing, but the familiar song of soZitarnous may be heard throughout the winter. This species, far more than the warbling and Philadelphia vireos, was likely to accompany the composite flocks of visiting warbiers."

Mr. Skutch writes to me: "The blue-headed vireo winters in northem Central America but has not been recorded south of Nicaragua. In Guatemala it is abundant through the winter months. Avoiding extremes of altitude, it yet spreads over a wide vertical range, from 2,000 to 9,000 feet above sea level. In December and January I found it rather abundant among the shade trees of the coffee plantations on the Pacific slope, at 3,000 to 4,000 feet above sea level. At higher elevations it frequents the forests of oak, alder, pine, and arbutus. During the year I passed on the Sierra de Tecp~n in the Department of Chiinaltenango, I found it wintering in small numbers between 8,000 and 9,000 feet. True to its name .solitarius, it never forms companies of its own kind; yet it is not entirely a hermit, for a single blue-headed vireo is often met in one of the mixed flocks of small birds that are so conspicuous a feature of the highlands during the winter months. The nucleus of each flock is made up of the excessively abundant wintering Townsend warblers, and about this gathers a motley assemblage of warbiers of other kinds, vireos, flycatchers, woodhewers, hairy woodpeckers, etc. Only with extreme rarity will the blue-headed vireo which has attached itself to a flock tolerate the presence of a second individual of its kind.

"On the Sierra de Tecp~n, the blue-headed vireo arrived on October 10, 1933. My latest spring date for the same year was April 28; but after the 19th I saw only this single individual. Griscom (1932) gives the extreme dates for the presence of this vireo in Guatemala as October 15 and April 27."

DISTRIBUTION
Range: North-central Canada to Nicaragua.

Breeding range: The solitary or blue-headed vireo breeds north to southern British Columbia (Comox, Puntchesakut Lake, and Sixteen-mile Lake); central western Alberta (Grand Prairie and Peace River Landing) ; southwestern Mackenzie (Nahanni River, Simpson, Hay River, and Fort Smith); northeastern Alberta (Chippewyan); central Saskatchewan (Lake Ile-a-la-Crosse, Emma Lake, and Hudson Bay Junction); central Manitoba (Grand Rapids and Knee Lake, probably); Ontario (Port Arthur, Moose Factory, Lake Abitibi, Algonquin Park, and Ottawa); southern Quebec (Blue Sea Lake, Quebec, Grand Greve, and probably Seven Islands); and extreme southwestern Newfoundland (Tompkins). East to southwestern Newfoundland (Tompkins;) ; Nova Scotia. (Baddeck, Pictou, and Halifax) ; Maine (Calais, Ellsworth, and Portland) ; Massachusetts (Boston, Taunton, and New Bedford); Connecticut (New Haven); northern New Jersey (Lake Mashipacong) ; and south through the Appalachian Mountains to northern Georgia (Brasstown Bald, Oglethorpe Ridge, ~nd Burnt Mountain). In comparatively recent years the mountain vireo of the southern Appalachians has extended its range to lower altitudes, and in North Carolina has been found breeding at Statesyille and Charlotte, and a few times at Raleigh, and in Georgia at Athens and Round Oak. South to northern Georgia (Burnt Mountain), northeastern Ohio (Ashtabula); extreme southern Ontario (Point Pelee) ; southeastern Michigan (Rochester) ; southern Wisconsin (Racine, North Freedom, and Prairie du Sac) ; central Minnesota (North Pacific Junction, Brainerd, and Itaska State Park); northern North Dakota (Pembina and Turtle Mountains); eastern Wyoming (Sundance and Laramie) ; central Colorado (Boulder, Denver, Colorado Springs, and Trinidad); central New Mexico (Santa Fe, Las Vegas, and San Antonio); western Texas (Guadelupe Mountains, Davis Mountains, and Brewster County); northern Chihuahua (San Diego and Pachico) ; central Sonora (Moctezun{a), and northern Lower California (Sierra San Pedro M~irtir). A resident race is found in the Cape district of Lower California. West to northern Lower California (Sierra San Pedro Martir) ; western California (Campo, Pasadena, Almaden, Oakland, and Eureka) ; western Oregon (Coos Bay, Corvallis, the mountains near Tillamook, and Portland); western Washington (Vancouver, Seattle, Lake Crescent, and Bellingham); and western British Columbia (Victoria, Comox, and Puntchesakut Lake).

Winter range: Th winter the solitary vireo is found north to northern Michoac~n (Cerro Patamban and Zamora); possibly north to southern Sonora (Tesia) ; Puebla (Metaltoyuca); Nuevo Le6n (Monterrey); southern Texas (Harlingen, Houston, Cove, and Silsbee); southern Louisiana (Avery Island and New Orleans); southern Mississippi (Biloxi) ; southern Alabama (Prattville, occasionally) ; Georgia (Milledgeville and casually to Atlanta and Athens) ; and southern South Carolina, casually (Aiken, Summerville, and Charleston). East to coastal South Carolina (Charleston and Port Royal) ; Georgia (Savannah and St. Marys); Florida (St. Augustine, New Smyrna, and Royal Palm Park); Quintana Roo (Chunyaxche), and El Salvador (Mount Cacaquatique) ; and occasionally to northern Nicaragua (San Rafael del Norte). South to El Salvador. West to El Salvador (Mount Cacaquatique and Barra de Santiago); Guatemala (Duenas and Huehuetenango); Oaxaca (Tehuantepec and Juquila) ; Guerrero (Tlalixtaquilla and Chilpancingo); Michoac~n (Cerro Patamban); the Cape region of Lower California (Cape San Lucas), and possibly southern. Sonora (Tesia), and in small numbers in the vicinity of Tucson, Ariz.; a single record of winter occurrence at Pasadena, Calif. It is a rare migrant of winter resident in western Cuba (Habana).

The ranges as outlined apply to the species as a whole, which has been separated into five subspecies or geographic races. The typical race, the blue-headed vireo (V.8. 8olitaruLs) ,breeds from southwestern Mackenzie eastward and south to central Alberta, southern Manitoba, northern Minnesota, southeastern Michigan, northeastern Ohio, Massachusetts, and the mountains of central West Virginia and Pennsylvania; the mountain vireo (V. s. altioo~a) breeds in the Appalachian region from southern West Virginia and Virginia to Georgia; the pluinbeous vireo (V. s. p~umbeus) from northeastern Nevada, Utah, and southern Montana south to Arizona and northern Sonora, western Texas, and the mountains of Chihuahua and Veracruz; Cassin's vireo (V. 8. cassini) breeds from central British Columbia, southeastern Alberta, and northwestern Montana, through Idaho, western Nevada, and California to northern Lower California; the San Lucas vireo (V. 8. lucasanus) is resident in the Cape district of Lower California. Other races are resident in Central America.

Migration: Late dates of spring departure are: Guatemala: Tecpam, April 28. Mexico: Guerrero: Chilpancingo, April 20. Tamaulipas: Victoria, May 1. Florida: College Point, April 23. South Carolina: Aiken, April 22. Virginia: Naruna, May 4. District of Columbia: Washington, June 2. Pennsylvania: Doylestown, May 24. New York: Orient, May 3. Louisiana: Grand Isle, April 6. Mississippi: Biloxi, April 14. Arkansas: Winslow, May 8. Missouri: Columbia, May 28. Indiana: Bloomington, May 17.

Early dates of spring arrival are: Georgia: Dalton, March 8. South Carolina: Spartanburg, March 26. North Carolina: Raleigh, March 9. West Virginia: White Sulphur Springs, April 1. District of Columbia: Washington, April 6. Pennsylvania: Berwyn, April 8. New York: New York, April 16. Massachusetts: Amherst, April 19. Maine: Ellsworth, April 21. Nova Scotia: Wolfville, April 25. New Brunswick: Scotch Lake: May 2. Quebec: Montreal, May 3. Tennessee: Knoxville, April 4. Illinois: Chicago, April 27. Ohio: Sandusky, April 14. Michigan: Ann Arbor, May 1. Ontario: Hamilton, April 25. Missouri: St. Louis, April 20. Iowa: Marshalltown, April29. Wisconsin: Madison, May 2. Minnesota: Red Wing, May 1. Kansas-Harper, April 26. Manitoba: Aweme, May 2. New Mexico: Chloride, April 26. Colorado: Boulder, April 18. Wyoming: Laramie, May 7. Montana: Columbia Falls, April 26. Alberta: Glenevis, May 8. Mackenzie: Simpson, May 22. Utah: St. George, April 16. Idaho: Coeur d'Alene, April 19. California: Twenty-nine Palms, March 24. Oregon: Pinehurst, April 15. Washington: Shelton, April 8. British Columbia: Courtenay, April 3.

Late dates of fall departure are: British Columbia: Okanagan Landing, September 15. Washington: Seattle, September 10. Oregon: Eugene, October 13. California: Santa Barbara, November 7. Alberta: Islay, October 1. Montana: Fortine, September 18. Wyoming: Laramie, October 16. . Utah: Ogden, October 6. Colorado, Beulah, October 17. Manitoba: Aweme, September 30. Minnesota: St. Paul, October 6. Iowa: Iowa City, October 15. Missouri: Golumbia, October 20. Arkansas: Hot Springs, November 1. Wisconsin: Beloit, October 19. Michigan: Blaney Park, October 8. Ontario: Toronto, October 20. Ohio: Toledo, October 27. Indiana: Indianapolis, October 2. Kentucky: Bowling Green, November 4. Tennessee: Nashville, November 9. Newfoundland: Tompkins, September 18. New Brunswick: Scotch Lake, October 22. Quebec: Montreal, October 6. Maine: Dover-Foxcroft, October 27. Vermont: Wells River, October 19. Massachusetts: Marthas Vineyard, October 25. New York: Rhinebeck, October 20. Pennsylvania: Philadelphia, November 4. District of Columbia: Washington, November 5. West Virginia: Bluefield, October 27. Virginia: Lawrenceville, November 13. North Carolina: Weaverville, November 24.

Early dates of fall arrival are: Minnesota: Lanesboro, August 24. lowa: Hillsboro, August 23. Ohio: Oberlin, September 12. Illinois: Glen Ellyn, September 10. Arkansas: Monticello, August 29. Louisiana: Thibodaux, August 21. Mississippi: Oxford, October 2. District of Columbia: Washington, September 6. Virginia: Naruna, August 12. South Carolina: Charleston, October 23. Georgia: Round Oak, October 7. Alabama: Greensboro, October 23. Florida: Pensacola, September 21. Mexico: Guerrero, Taxco, October 10. Guatemala: Tecpan, October 10.

Egg dates: Arizona: 15 records, May 20 to July 9.

California: 100 records, April 26 to July 9; 52 records, May 20 to June 6, indicating the height of the season.

Massachusetts: 57 records, May 14 to July 29; 32 records, May 30 to June 18.

North Carolina: 16 records, April 12 to June 16; 8 records, April 18 to May 9. Washington: 37 records, May 1 to July 3; 20 records, June 3 to 16.



VIREO SOLITARIUS ALTICOLA Brewster
MOUNTAIN VIREO

HABITS

The mountain vireo deserves its name as an inhabitant of the mountains and adjacent valleys of the Appalachian Mountain system, the most typical birds being found in western North and South Carolina, eastern Tennessee, and northern Georgia. The 1931 Check-list extends the range northward to Maryland, but probably alticola intergrades with typical solita'riua somewhere in Maryland, the Virginias, and Pennsylvania. Prof. Maurice Brooks, in some notes he has sent me, points out the folly of trying to define too closely the ranges of subspecies by "creating an artificial barrier on the political boundary made famous by Mason and Dixon. * * * The situation as regards these vireos is exactly paralleled by slate-colored and Carolina juncos, and by black-throated blue and Cairns's warblers; in each case the southern birds are supposed to just reach the Pennsylvania border, where they are met by their northern relatives. It happens that all three species are abundant in the mountains on both sides of the line, and it is obvious that no sharp limits between the races can be defined; there is constant meeting and interbreeding."

I have sometimes been criticized because we have not attempted in this series of bulletins to outline accurately the ranges of the subspecies; the above remarks illustrate very clearly the futility of trying to do so in nearly all cases; in only a few isolated instances can this be done satisfactorily.

Thesummer range of the mountain vireo in the regions roughly outlined above extends from about 1,200 feet above sea level in the valleys to over 6,000 feet on mountain summits. In winter it retires from the mountains and lives in the lowlands of South Carolina, Georgia, and northern and central Florida.

William Brewster (1886) described and named this subspecies from specimens collected in Macon County, N. C. lie says:

This new form may be easily distinguished from soiitarias by its larger size, heavier bill, and different color of the upper parts. In 8olitarius the crown and sides of the head are clear, pure ash, in strong contrast with the olive green of the back and rump, whereas in aiticola the entire upper parts are nearly uniform blackish-plumbeous, with only a faint tinge of greenish on the back, which is essentially concolor with the crown. In these respects the bird resembles V. plum bcu,s, but its coloring above is darker and dingier, its sides strongly yellowish as in 8Olitarjus. ï * * Throughout the elevated plateau occupying the southeastern corner of Macon County, this new Virco was one of the most abundant forest birds. It was found exclusively in open oak and chestnut woods, where Its ringing voice, mingling with the rich music of the e~uaIly numerous Grosbeaks (Ha bia ludoviciana) and Scarlet Tanagers (Piranga crythromclas), was rarely still even at noontide.

Professor Brooks says in his notes: "Mountain vireos are characteristic and abundant birds of the southern highlands, found from the zone of spruce and balsam down to elevations of 1,200 or 1,500 feet in the mountain valleys. I have not found them at corresponding elevations away from the mountains, however; the common name seems abundantly justified."

Bruce P. Tyler (MS.) tells me where he finds this vireo in eastern Tennessee: "With us the ideal home of the mountain vireo is Shady Valley, in Johnson County, Tenn. This lovely valley is located between Holston and Iron Mountains. The floor of the valley is 3,000 to 2,500 feet elevation, decreasing as it departs from the upper reaches of Beaver Dam Creek and extends to 'Back Bone Rock' near Mock's Mill, about 10 miles as the crow flies. The valley is flanked by mountains with ultimate elevations approaching 4,000 feet; and, beyond Iron Mountain, we have White Top and Mount Rodgers, with elevations of 5,678 and 5,719 feet, respectively. These higher peaks reach well into the Canadian Zone. These summits seem, by their proximity, to lend something of the Canadian Zone flavor to Shady Valley. The flora of the valley smacks of the Canadian Zone. Originally the bed of the valley was a cranberry bog. Overmuch 'civilization,' W. P. A., etc., have drained and cleared it until, only by closest search can any cranberry vines be found. The mountain vireo breeds in the upper reaches of the Transition Zone and in the Canadian Zone."

Mount Mitchell, in western North Carolina, is said to be the highest mountain in the eastern half of the United States, rising 6,684 feet above sea level; it was once covered with a dense forest of tall red spruce; but logging and forest fires have destroyed all but a narrow fringe of spruces at the summit. Thomas D. Burleigh (1941) found the mountain vireo to be "a fairly plentiful breeding bird in the fir and spruce woods at the top of the mountain. In the valleys the first spring migrants appear during the latter part of March, but April 12 (1930) is the earliest that this species has been noted in the open spruce woods (5,000 feet), and not until May 4 (1933) has the first venturesome individual been seen at the top of the mountain (6,600 feet). The latest date for occurrence in the fall is September 30, (1930) ."

Nesting: Professor Brooks writes to me from West Virginia: "Woodland openings, trailsides, picnic grounds, and such natural or artificial disturbances of the forest are most frequently chosen as nesting areas by these birds. Yellow birch is a favorite nesting tree, the yellow-brown bark furnishing nesting material and, very often, an effective concealing background for the nest. Nearly every nest I have examined has contained fibers of birch bark. Nests are placed from 6 to 15 feet from the ground, usually just out of reach."

Bruce P. Tyler tells me that, in his Shady Valley region, the nest of the mountain vireo "is placed in the fork of the lower branches of a tree or a fork of a low branch of undergrowth in the woodland. It is more globular than the nests of the red-eyed or white-eyed vireo and somewhat larger." He has sent me a fine photograph (pL 38) of a nest, taken in this valley on June 12, 1938. "This nest was placed in a red oak tree, 20 feet up and 7 feet out from the trunk of the tree. It was made of grass, shredded bark and plant fiber and covered with lichens, bound together with spider webs. The bird remained on the nest until the limb which supported it was cut off." The nest contained four eggs which had been incubated for three or four days.

Pearson and the Brimleys (1942) say that, in the mountains of North Carolina, "it breeds chiefly in deciduous trees." They record nests in a chestnut, a small sourwood, another chestnut, and an oak.

Mr. Burleigh (1925) seems to be satisfied that, in northeastern Georgia, "two broods are raised each year, the first during the latter part of April and early May, and the second in June." He says further:

Nests from which the young bad already flown were found early in June, and my experience would certainly prove the later nestings. The first nest with eggs was found June 14, holding on that date four well incubated eggs. It was twenty-five feet from the ground suspended from a fork at the outer end of a 11mb of a large hemlock close to a stream in a ravine, at the foot of Brasstown Bald. A second nest, found June 19, also held four well Incubated eggs and was eighteen feet from the ground suspended from a fork at the outer end of a limb of a beech sapling well up the mountain side. The female was incubating and was remarkably tame, remaining on the nest until the limb was cut off and the nest brought within reach, flying only when stroked on the back. A third nest found June 25 held one fresh egg and was later deserted. It was twelve feet from the ground at the outer end of a limb of an uprooted ash sapling in a ravine probably half way up the mountain. These nests were all alike in construction, being compactly built of grasses, fragments of weed stems and shreds of bark, lined with fine grasses, vine tendrils and fine hemlock twigs, and well covered on the outside with, in two cases, fragments of an old hornet's nest, and invariably numerous green lichens. * * As confirming my opinion that two broods are raised each year, I might add here the fact that a fourth nest was found July 15, in Fannin County, that held newly, hatched young.

Mr. Brewster (1888) received what was probably the first nest of this subspecies ever reported. It was taken by J. S. Cams on May 27, 1887, on Craggy Mountain, Buncombe County, N. C. "It measures externally 3.25 in diameter by 2.10 in depth. In places the rim is nearly an inch in thickness. The exterior is beautifully diversified with white and purplish-brown sheep's wool, grayish lichens, small strips and fragments of decayed wood, and a few spider's cocoons, bound firmly to, or hanging loosely from, the framework proper, which is composed of coarse grass stalks and strips of bark, the latter partly a reddish-colored inner bark, probably from the hemlock, but largely the pale gold, sheeny outer bark of the yellow birch (B. lutea). The interior cavity is lined with fine bleached grasses and the reddish stems of some species of club moss."

R. B. McLaughlin (1888), of Statesville, N. C., found two nests of the mountain vireo in some high, dry woods, consisting wholly of pines, such as those in which the pine warbler nests. One nest was in a small, slim pine, and the other was "attached to the limb of a tall, slender pine, about forty feet from the ground and ten feet from the body of the tree." On June 2, while the birds were building the first nest, they were followed by three young of a previous brood, which is further evidence that this vireo raises two broods in a season.

Eggs: The mountain vireo lays ordinarily three or four eggs, most often four in a full set, and perhaps rarely five, though I find no record of five. These are similar to those of the northern bluehead, but averaging slightly larger. The ground color is sometimes creamy or pinkish white, and the spots are apt to be in lighter shades of brown, sometimes almost reddish brown, with washed-out edges; some eggs are more heavily marked than those of the northern bird. The measurements of 40 eggs average 19.7 by 14.5 millimeters; the eggs showing the four extremes measure 21.6 by 14.3, 20.2 by 15.0, 18.4 by 14.0, and 21.3 by 12.4 millimeters.

The food of this vireo is included under the report on the type race, and the plumage changes, behavior, and voice are not materially different from those of the blue-headed vireo. Many observers have praised the beautiful song of the mountain vireo, but most of them have compared it with the songs of the redeye or white-eye, which are, of course, inferior or at least less pleasing. But Mr. Brewster (1880) says: "Its song was somewhat like that of eolita'rius, but to my ear much finer, many of the notes being louder and sweeter, and the whole performance more continuous and flowing." And Mr. Wayne (1910) states: "The song of this form is much richer in tone and volume than that of its near relative, the Blue-headed Vireo."

A. L. Pickens thinks this vireo should have specific rating on the merits of its voice, and says in a letter to me: "The mountain vireo takes the standard vireo syllables, with all their distinctness, and adds two syllables like an accompaniment blown on some woodland flute, and the most matter-of-fact oratory of the vireos becomes something worth climbing mountains and pushing through thickets to hear."

SAN LUCAS VIREO
VIREO SOLITARIUS LUCASANUS Brewster
HABITS

William Brewster (1891),il describing and naming this vireo, says:

This Vireo although averaging considerably smaller than V. 8. cassinji has a bill as large and stout as in V. s. alticota. In the coloring of the upper parts all my spring and summer specimens agree closely with cassiaii hut there is a decided and very constant difference in the color of the flanks and sides, these having Quite as much yellow as, but mach less greenish than, V. solitariu~. In autumnal plumage the Lower California hird approaches autumnal specimens of sobiterius very closely, having the upper parts quite as bright olive green, the wing-bands as yellow, and the head nearly as clear ashy. There is also fully as much yellow on the sides, but much less greenish. These characteristics, with the aimost total lack of brownish beneath, distinguish it readily from young Ca88iflit.

Mr. Brewster (1902) says of its range: "So far as known, this Vireo is strictly confined to the Cape Region, where it is found at all seasons of the year, although most numerously, perhaps, in summer. Its breeding range extends from the coast at San Jos6 del Cabo, where it occurs almost exclusively in cultivated grounds about houses, to Miraflores and San J05~ del Rancho, at both of which places it is common. Only a few were seen by Mr. Frazar at Triunfo, and none on the Sierra de la Laguna, while but one was taken (on April 4) at La Paz, which appears to be beyond the northern limits of its usual range.~~ It is of interest to note that this race seems to be entirely isolated, as no form of the blue-headed vireo species is known to breed in the wide gap between La Paz on the south and the Sierra San Pedro M~rtir on the north.

Nesting: Mr. Brewster (1902) writes: "A nest of V. s. lucasanu8 containing four fresh eggs, found by Mr. Frazar at San Jos~ del Rancho on July 15, was suspended in a fork at the extremity of a long, lea /less branch of an oak at a height of about fifteen feet. It is composed chiefly of a gray, hemp-like fiber mixed with grass stems and thin strips of bark. There are also a few spiders' cocoons loosely attached to the bottom and sides, and apparently intended as ornaments. The interior is very neatly lined with fine, wiry, reddish-brown grass circularly arranged. The nest measures externally 3.00 in diameter by 2.50 in depth; internally, 2.00 in diameter by 1.50 in depth. The walls are half an inch thick in places."

J. Stuart Rowley writes to me: "While walking through the woods on San Bernardo Mountain, on the Gulf slope of the Sierra de la Laguna, I heard the unmistakable song of a solitary vireo, and, by carefully tracing the song to its source, I finally discovered the bird sitting on the nest." Charles E. Doe, who now has this nest in the University of Florida, tells me that it is a beautiful nest, made of fibers and moss, and placed 12 feet from the ground in a small oak; it was taken on May 6, 1933.

Eggs: Both of the sets mentioned above, the only sets of which I have any record, contained four eggs each. Mr. Brewster's eggs are white, "with a sligl~it creamy tint, and are spotted, chiefly about the larger ends, with reddish brown and black." The measurements of the eight eggs average 20.5 by 14.3 millimeters; the eggs showing the four extremes measure 21.1 by 13.8, 20.5 by 15.3, 19.9 by 14.3, and 20.2 by 13.8 millimeters.

Why do birds stand on one leg?

The professor has the answer!