Yellow-throated Vireo

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 Yellow-throated Vireo – the common name and sub-species reflect the nomenclature in use at the time the description was written.

This handsome vireo, the most brilliantly colored of the family, is widely distributed over the eastern half of the United States and southern Canada, but it is not equally common everywhere throughout this wide range, and it is uncommon or rare in many places. When I was a boy it was a common bird in southeastern Massachusetts, and we often saw its beautiful nests in our shade trees and orchards; but now, alas, it is only a happy memory; I have not seen one here for many years. It has probably gone from many another of its former habitats. I have always suspected that its disappearance was largely due to the extensive spraying of our shade and orchard trees. The red-eyed vireo, also, seems to have been driven away from our home grounds and the shade trees along our streets, probably for the same reason, but it is still common enough in our deciduous woodlands. The yellow-throated vireo, in my experience, has never been as much of a woodland bird as the redeye and far less so than the closely related blue-headed vireo. Dr. Brewer (Baird, Brewer, and Ridgway, 1874) expresses it very well as follows: “All the older ornithological writers, in speaking of the Yellow-throated Vireo, repeat each other in describing it as peculiarly attracted to the forest, seeking its solitudes and gleaning its food chiefly among its topmost branches. Such has not been my experience with this interesting and attractive little songster. I have found no one of this genus, not even the gilva, so common in the vicinity of dwellings, or more familiar and fearless in its intercourse with man.”

It is only fair to say, however, that Dr. Brewer’s observations were evidently made near Boston, Mass., where its haunts were much as they used to be here. In other portions of its range, and to some extent in the east, it may be found on the edges of woodlands, in groves and in open stands of oaks, maples, and other hardwood trees, but seldom in the dense forests. Dr. Dayton Stoner (1932), referring to the Oneida Lake region in New York, writes: “It seems to be more widely dispersed in early spring than later when its local distribution becomes more restricted, being then confined largely to orchards and groves, the vicinity of cottages and summer camps, tall roadside trees and those in the villages about the lake. I have been particularly impressed by the numbers of yellow-throated vireos about the villages of Bridgeport and Cleveland during the summer. Wooded tracts composed largely or solely of tall maples, wild black cherry and other hardwoods * * * also appeal to this vireo.”

Probably in such localities the yellow-throated vireo would be likely to survive longer than in the much-sprayed roadside trees and orchards of Massachusetts.

Nesting: The yellow-throated vireo builds the handsomest nest of any of the virt ~s, even prettier than the best examples of the nests of the blue-headed vireo, and fully as well decorated as the nests of the hummingbird, wood pewee, and blue-gray gnatcatcher, though differing from all these in shape and suspended from the prongs of a forked twig. The general construction of the nest is similar to that of other vireos, but it is very well made and firmly attached to the supporting twigs. In one before me the supporting twigs are entirely concealed by the masses of cobwebs and other material that have been tightly drawn over them and covered with lichens; the whole body of the nest is almost completely covered with small bits of variously colored tree lichens, all held securely in place by numerous fine strands of spider silk; the deep cup, with its thick walls and incurving rim above it, is neatly lined with fine grass tops. lit measures approximately 3 inches in outside diameter and about 2½ inches in outside depth; internally the cup is about 2 inches in diameter at the top and 1% inches deep; the bulging sides make the inner cavity wider below the rim, thus giving the eggs or young more security as the nest is swayed in the wind.

The nests of the yellow-throated vireo are placed in a variety of deciduous trees, but rarely in conifers. The height from the ground varies from 3 feet to 60 feet; apparently most of them are over 20 feet up. A nest was built in a tuliptree close to my house, about 20 feet above the ground, attached to a forked twig that projected from a horizontal branch in the middle of the large tree, and within a few yards of my dressing-room window. The nest, now in my collection, is beautifully decorated with the egg cases of spiders and green and gray tree lichens, firmly secured with spider silk and lined with fine, dry needles of the white pine. I have found a number of nests in old, neglected apple orchards; these were also fully camouflaged with lichens picked from the branches and trunks of the old lichencovered trees, so that they blended beautifully xvith their surroundings and were easily overlooked.

Dr. Brewer (Baird, Brewer, and Ridgway, 1874) writes:

All of its nests that I have ever met with have been built in gardens and orchards, and in close proximity to dwellings, and they have also been exclusively in comparatively low positions. In one of the most recent Instances a pair of these birds built one of their beautiful moss-covered nests In a low branch of an apple tree that overhung the croquet ground, within a few rods of my house. It was first noticed in consequence of Its bold little builder flying In my face whenever I approached too near, even before its nest contained any eggs. The grounds were in frequent use, and the pair were at first a good deal disturbed by these constant intrusions, but they soon became reconciled to their company, and would not leave their position, even though the game was contested immediately under their nest, which was thus often brought within a foot of the heads of the players. Before this nest was quite finished, the female began her duties of incubation. Her assiduous mate was constantly engaged at first in completing the external ornamentation of the nest with lichens and mosses, and then with a renewal of his interrupted concerts of song. These duties be varied by frequent captures of insects, winged and creeping, most of which he duly carried to his mate.

Edward B. Ford sends me the following notes: “Of 14 nests of the yellow-throated vireo, found in Newaygo County, Mich., my notes lack desirable detail because of the height at which they were placed, 25 to 40 feet from the ground. However, all nests had this in common: They were placed within the crown of the tree on small, sturdy branches at right angles to the trunk, or to a large upright fork thereof. At the point of attachment to the supporting branch, the nests were within from 12 to 20 inches of the trunk or fork. Except in two instances of comparatively low nests, they were built in rather large oaks or, once, in a wild cherry. One low nest was in a small oak, the other in an apple tree. Four nests were placed near, or directly above, the roof of some cottage or out building near the shore of Hess Lake. All the nests found were not far from the lake, and some were in the woods, apart from man-made structures.

“An unusual circumstance was the use of a repaired and redecorated nest of the previous year. This brought forth a brood in the first part of June. One pair was observed to carry nesting material to two separate sites, about 20 yards apart. On the second day work ceased at one site, near a building, but was continued at the other until the nest was completed. Like other vireos, this species is strongly attached to the nest. One bird that I attempted to remove by lifting it from the nest was so obdurate that I gave up, fearful of damaging the contents.”

A. Dawes Du Bois writes to me: “In 1933, while selecting a spot for planting some wild anemones, I chanced to see a yellow-throated vireo at work on a nest in a basswood tree near the corner of our house. The nest could be seen from the bathroom window, which was about on a level with it and only 25 feet away. The nest seemed about in the midstage of construction. Both birds were working industriously; sometimes one would come before the other left. The procedure was of three kinds: (1) to place material inside of the nest; (2) to work from outside the nest, pulling material upward and outward over the rim and over the supporting twigs; (3) to get inside the nest and work with the feet, shaping and enlarging the nest, and stretching it to greater depth. The last action showed plainly from the outside, as the bird pushed the nest out into humps in various parts of the bottom.

“The vireos worked all the next day (May 20). They chased invading birds away with a vim. On two occasions, when a bird was working inside the nest, I observed that its body was in practically a vertical position, head in bottom of nest, tail approximately straight up. They continued to work at the nest on the 21st. Once I saw her carrying a large patch of white cocoon material.

“I did not see them doing any work on the 22d. On the 23d the wind blew a gale all day, bringing a dust storm in the afternoon. Twice, in the afternoon, I saw one of the birds working at the rim of the nest, where it was attached to the branchiet, probably repairing damage. The next morning the nest was pretty badly wrecked; and the wind continued. When I returned in the afternoon it had been blown out of the tree. I found it on the round; evidently it had not been completed.”

N. S. Goss (1891) found a nest of the yellow-throated vireo, in the timber near Neosho Falls, Kans., “attached to branches of a very small horizontal limb of a large hickory tree, about twenty feet from the ground, and ten feet below the limbs that formed the top of the tree. In the forks of the tree the Cooper’s Hawks were nesting, and I discovered the Vireo and its nest in watching the Hawks: or rather the man I had hired to climb the tree to the Hawks’ nest.” He continues:

I have since noticed these birds in the woodlands on several occasions, and on the 18th of May, 1883, while strolling along the south bank of the Kansas River, near Topeka, in the timber skirting the stream, I had the pleasure to find a pair of them building a nest in a honey locust, about sixteen feet from the ground, and eight feet from the body of the tree. The nest was fastened to the forks of a small horizontal branch. The frame of the nest appeared to be completed. The birds were busy at work, the female lining the nest with small, hair-like stems, the male covering the outside with soft, lint-like fibrous stripplings from plants (these closely resembling the limb and its surroundings), and dotting it over with lichen. * * * As the female stood upon the top of the nest, with head down and inside, I could not see the manner of arranging the lining; but as she kept walking around upon the rim, I could, In imagination, see her plaiting and weaving in and out the hair-like stems. It was very easy and interesting, however, to see and note the actions of the male, as he deftly worked the material into the framework, running the longer, fibrous, thread-like strips through, and then quickly springing upon the top, and fastening them on the Inside. Then he would rearrange the outside, stopping a moment to inspect the work, and then off in search of more material, occasionally warbling a few notes on the way; but he was silent at the nest, while I remained so near.

John Hutchins (1902) gives a full account of the building of their nest by a pair of yellow-throated vireos close to his house in Litchfield, Conn.:

The discovery of the nest-building was made, as is so often the case, by seeing the bird gathering material. We were passing near the stable, when underneath Its rather deep eaves a small bird was seen to be fluttering, and we thought she was caught in a strong spider’s web, as before now I have found our Hummingbird; but instead of this the bird was gathering web for her uses, and soon flew away to the front of the house, where we lost sight of her; but on coming up cautiously we had the great joy of seeing her fastening the first sticky threads of her new home to some outstretched twigs of a small low-growing elm branch close by our window. * * * The birds began their building on Sunday morning, June 2. By the following Saturday, June 8, the nest was completed, so that they took about one round week of not hurried, but of quite incessant work to complete their home-making. * * * The material for the nest was almost all of spider-web. * * * And there were occasional thread-like shreds of some coarser fiber in the Yellow-throats’ building, but by far the larger part was of the twisted films of the spider. * * * The birds built the rim of their nest stout and strong, twisting the web about the twigs and over and over upon itself where it stretched from twig to twig till I wondered at their ingenuity and patience. Their little beaks reminded me of the needle of the sewing machine with its eye at the pointed end. * * * Inside and outside the little heads wonid reach, with the prettiest turns and curvetings imaginable, till, as the nest grew deeper, the work was done more and more from the inside. Then it was gathered together at the bottom, with side joined to side. When this part of the work first took place the nest seemed to be strangely lacking in depth and had an unshapely look altogether.

But this was the point where the full revelation came to me of how the deepest part is shaped. I saw the bird at this stage inside the nest raise her wings against the upper rim and the twigs which held it and strain with her wings upward and her feet downward till the nest itself grew so thin that I could see through it In places. Then they began again, for the most part from the inside, weaving in more material to thicken and strengthen sides and bottom where these had become thin and weak through the stretching. This was done many times over until the proper depth and thickness were both secured. The nest after being stretched out In this way would be like the coarse warp of a fabric on a loom, and into this the little weavers wove their silken threads.

After this came the embellishing with the bits of lichen. These were brought, and fastened on by means of little filmy threads of the spider drawn from the surface of the nest and fastened doiva over the moss.

Samuel A. Grimes has sent me two fine photographs of Florida nests (pl. 33), one in a blackjack oak and one in a loblolly pine. Nests have been found in other trees than those mentioned above, mostly in various oaks and maples, but also in beech, chestnut, and elm; probably some other trees could be added to the list. About one week seems to be the average time required to build the nest.

Eggs: The yellow-throated vireo lays three to five eggs to a set, usually four. The normal shape is ovate, but some are slightly pointed and some are more oval. They are the handsomest and most heavily marked of any of the eggs of the vireos. The ground color varies from pure white to creamy white or pinkish white, these tints often remaining persistent in the collector’s cabinet. They are quite strongly spotted, mostly at the larger end, with various shades of brown, reddish brown, chestnut, vinaceous-cinnamon, dark brown, blackish, or different shades of drab or lavender; some of the spots are large enough to be called blotches, even such as occur on kingbirds’ eggs, but such extremes are very rare; even more rarely, an egg may be nearly, or quite, immaculate. The larger spots often show a washed-out effect around their edges. The measurements of 50 eggs average 20.8 by 14.9 millimeters; the eggs showing the four extremes measure 22.8 by 16.0, 17.9 by 13.6, and 18.8 by 13.2 millimeters.

Young: The period of incubation for the yellow-throated virco seems to be about two weeks, and the young remain in the nest for about the same length of time. Very little study of this subject seems to have been made, but Mr. Hutchins (1902) gives us the following information on it: “After the sitting proper seemed to have begun it was in about two weeks’ time that we saw the first signs of life in the nest. The male bird took his part with the female in the incubating. lie would bring food to her as she sat upon the nest and, I am not quite sure, but think that she did the same with him. * * * My Yellow-throats were very faithful to their young, of which there were three. The male fed them as attentively as did the mother. On July 7, nearly a month from the beginning of the brooding, the first young bird left the nest. It seemed to take good care of itself, keeping to the trees, and the next day the other two followed it.”

He discovered great clutching power in the feet of one of the young that he picked up on the lawn. This was evidently of great service to the young while tossed about in the nest, for he says: “Through many thunder storms which came to us in that month of June I have seen that slight branch from the body of the elm whip in the blast as if it would be torn from its setting in the great trunk. The nest would betop-down and driven every way, and yet never a fledgling fell from its place. No wonder there had come a development of clutching power I” Plurnages: Dr. Dwight (1900) says that the natal down of the yellow-throated virco is drab, and he describes the juvenal plumage as “above, smoke-gray. Wings and tail black, edged with olive-gray, the secondaries and tertiaries with olive-green (the two inner tertiaries white edged), the greater and median coverts with dull white forming two wing bands. Below, silky white, the chin, throat and sides of head pale canary-yellow, the orbital ring, ocular region and superciliary stripe still paler.”

A partial postjuvenal molt, involving all the contour plumage and the wing coverts, but not the rest of the wings or the tail, occurs in July and August. This produces the first winter plumage, which is practically indistinguishable from that of the adult. The upperparts are now bright olive-green, the wing bars are pure white, and the throat and breast are bright canary yellow.

The sexes are much alike in all plumages, but the female is usually somewhat paler than the male in adult plumage. There is appar. ently no spring molt, and wear and fading are not pronounced. There is a complete postnuptial molt late in summer, mainly in August.

Food: Reporting on the contents of 160 stomachs of the yellowthroated vireo, collected during the months of April to September, inclusive, Dr. Edward A. Chapin (1925) says: “The yellow-throated vireo eats comparatively little vegetable food, practically none during April and May, none during June and July, less than 2 percent in August, and less than 9 percent in September. The average for the year is only 1.74 percent. Among the items specifically determined were sassafras berries and seeds of wild grapes. No cultivated fruit of any kind was found.”

The animal food was made up of 95.82 percent insects, 2.38 percent spiders, and 0.06 percent other animal matter. Lepidoptera, butterflies and moths in their various stages, constituted the largest item, more than 42 percent of the whole, of which caterpillars amounted to more than half of this, 23.1 percent. Most of the adults were moths, 19.35 percent. Hemiptera, true bugs, occupied second place, stink bugs amounting to 15.5 percent, and the remaining ‘1.62 percent including such forms as assassin bugs, scale insects, and leaf hoppers. “Beetles of all kinds, making up 12.9 percent of the yearly food, stand third in the diet. Ladybird beetles, usually plentifully found in the stomachs of vireos, in this species amount to less than 1 percent of the total.” The injurious beetles eaten include weevils, wood-boring forms (Buprestidae and Cerambycidae), the plant-feeding Elateridae, dung beetles and leaf chafers (Scarabaeidae), leaf beetles (Chrysomelidee), and ladybird beetles (Coccinellidee). Diptera make up 7.36 percent, Hymenoptera 5.07 percent, and other insects 4.92 percent. No honey bees were identified, but there were some sawflies and ichneumon-flies. The other insects eaten include grasshoppers, crickets, locusts, dragonflies, cicadas, mosquitoes, midges, and plant lice.

Behavior: On its nest the yellow-throated vireo, like the blueheaded vireo, is a close and steadfast sitter, allowing close approach and even handling; it cannot easily be driven from its nest and must often be removed forcibly, sometimes with difficulty. It seems quite fearless in the presence of humans; Francis Orcutt (1928) tells of one that came and fed a young bird several times while he held the little one in his hand, perching on his thumb or finger. It is, however, sometimes quite aggressive when its nest is approached, attempting to drive away the intruder by scolding and threatening to attack him. Dr. Brewer (Baird, Brewer, and Ridgway, 1874) writes:

They are somewhat confiding and trustful of man, are readily approached, and soon become so well acquainted with those among whom they have a home as to fearlessly come to the windows of the house in pursuit of spiders or flies, and even to enter them. In the latter case they cannot readily make their exit, and soon lose their self-possession, heating their heads against the walls and ceiling in vain attempts to get out, unless caught and released. In one instance a young bird, that had entered my barn-chamber, became so entangled in cobwebs, around his wings and feet, as to be unable to escape again. When taken in the hand, and his meshes one by one picked out from about his feet and quills, he was very docile, made no resistance or outcry, nor any attempt to escape, until he was entirely freed from his bonds, although It required some time and care to accomplish it. When entirely freed from these clogs, and permitted to go, he flew away very deliberately to a short distance, and occupied himself with dressing his disordered plumage.

Voice: Aretas A. Saunders has given me the following elaborate account of the song and call notes of this vireo: “The song of the yellow-throated vireo is long continued, consisting of short phrases separated by pauses. In this respect it is like the songs of the blueheaded and red-eyed vireos, but there are a number of differences, some apparent when we listen carefully to the bird, others appearing only when the song is recorded and studied.

“The yellow-throated vireo’s song is slower than those of the other vireos, the pauses between phrases being longer. The quality of the sound is rather reedy and less clear than the others. The pitch is lower. The number of different phrases is less, and the bird is inclined to repeat two to four of them in a regular order. The notes of the phrases are usually slurred together, so that they sound like eeyay, ayo, or ahweeo, etc.

“In the records I have of 52 different birds the pitch varies from o ‘ ‘ ‘ ‘toB ‘ ‘. OnlyonebirdsangtoC ‘ ‘ ‘ ‘,themajorityhaving A ‘ ‘ ‘ or G ‘ ‘ ‘ for the highest note. The rate of singing varied from one phrase every four-fifths of a second to one every 2 seconds. Individuals possess five to nine different phrases, but frequently sing only two or three of them for so long a time that patient listening is required to get them all. The phrases are commonly of two or three notes. In all my records there are just two phrases of four notes, and none with more than that. Two-note phrases that slur downward are much commoner than those that slur upward; that is, ayoh is a commoner phrase than oway. In the same manner in 3-note phrases, such a phrase as oweeah is commoner than eeoway.

“The period of song is from arrival early in spring to early in August. The song is revived again late in August or early in September. It is impossible to give definite dates of cessation, for though each individual stops singing for a time, that time is so short, and the difference in individuals so great, that there is no certain period of complete silence for the species, and one cannot be sure, when birds are heard in mid-August, whether it is the last of the regular period or the beginning of the revival. The song is not heard in September every year, but in 14 years in which I have definite dates, the average is September 8, and the latest September 18, 1939.

“The yellow-throated vireo has a soft musical call noteï running down in pitch, and with a trilly sound. I have written it in my notes as ‘wkree-wliree-orrrr. An alarm note is a series of notes, also descending in pitch, chi-ohi-cka-cka-cltu-chu. Both of these notes bear a strong resemblance to corresponding calls used by the blue-headed vlreo” Mr. Skutch writes to me from Costa Rica: “Like the blue-headed vireo, the yellow-throat sings much in its winter home. It is in a songful mood upon its arrival late in September or October; and although it may fall silent during the wet closing months of the year, from January until its departure in late March or April, it frequently delivers its queer, halting song. Indeed, in many parts of its winter range, the species is so rare that it would probably he overlooked but for its habit of proclaiming itself at a season when most of the migrants: and a large proportion of the resident birds, too: are songless.”

Mr. Ford mentions in his notes “a disturbed trill, which may be likened to the wing sound of a flushed mourning dove, albeit much diminished. This seems to be used only when the bird is in attendance upon the young. Its scolding note is unlike the whining complaint of the warbling vireo and the red-eye. It is a sort of chatter, in tone similar to that of the agitated house wren.” These are, apparently, the same notes as those described above by Mr. Saunders.

Francis H. Allen writes to me: “A call note that I have heard in May and which may be connected with courtship is a low hew. Another record of a note heard in early May reads something like 88WiflJC or sswinkel.” Elsewhere (1922) he describes another song: “The song consisted of several repetitions of a high-pitched note with rising inflection, suggesting the goldfish’s call note, but less clear and less prolonged, followed by shorter, indefinite notes and then by the rolling trill, then more of the high-pitched notes, and so on: a sort of continuous performance, perhaps not always in this precise order, but having the trills interspersed with these long and short notes. The characteristic chatter of the yellow-throated vireo was also thrown in occasionally. The bird dropped this song presently and began its ordinary song.”

E. P. Bicknell (1884) observed one of these vireos singing on the wing:

On May 21, 1882, I observed a pair flying about among an open group of trees; one was being followed by the other; but their motions betrayed none of the excitement of pursuer and pursued; their flight was so easy and leisurely that it was almost restful to watch them. For more than a minute they continued slowly circling about among the trees, within a space of a few rods, passing In and out among the branches; several times the leading bird appeared about to alight, but feeling its pursuer close at hand continued its course. The rear bird was constantly giving utterance to its full song notes, which fact probably accounts for its uninterested manner ns pursuer; for it seemed so engrossed with the feat of singing during flight that it could give little heed to the chase. Both birds finally alighted peaceably among the branches, the follower alighting first.

This may have been part of a courtship display, in which the male was showing off his powers of song.

Albert R. Brand (1938) found that the pitch of the yellow-throated vireo’s song was far below the average for passerine birds; the approximate mean was 2,750, the highest note 3,825 and the lowest 2,325 ~ ibrations per second.

The fact that the yallow-throated vireo has been heard to sing the song of the blue-headed vireo, several times by competent observers, and that the bluehead has been observed to sing the yellowthroat’s song, suggests that these two closely related species may occasionally hybridize; and there is some evidence to support this theory. William Brewster (1906) reported that, during two seasons, a blue-headed vireo repeatedly sang both songs in his garden; and he suggested the possibility that it might have been paired with a yellow-throated vireo, though he had no evidence to prove it. Dr. Charles W. Townsend (1920) says: “On May 8, 1919, a bird that sang the wild clear song of the blue-headed vireo so that there seemed to be no mistake about its identity turned out to be be a yellow-throated viree.” And Bagg and Eliot (1937) have this to say on the subject.

Throughout the fifteen years 1921: 35, accordIng to Pro!. Eliot, the Smith College Yellow-breast has sung the same song. * * In 1930 (but not again) another male took up quarters in the same neighborhood who sang two songs: his own species’ nnd the Blue-headed Vireo’s. Inspection showed that he looked darker, especially about the head, than normal for his kind; and suspicion was at least aroused that in the scarcity of Yellow-throated females his father (presumably the Smith College male), perhaps widowed, had persuaded a Blue-head to mate with him, the year before. * * * In Agawam on May 26, 1936, the song of a blue-head, seeming very out of place, was looked up and found to issue from a typical-looking Yellow-breast (Eliot). Apparently the fiavifroas coloration is “dominant” in hybrids. Prohably it was that of the two species’ common ancestor, and solitarius originated as a northern variant or “sport”. * * * On June 22, 1936, near Mt. Tekoa (not at all Yellow-breast country), Mr. Dietrich studied a Blue-head with a yellow wash on the throat and “incomplete eye-ring”: possibly the effect of Yellow-breast blood?

This is an interesting theory, but it is strange that no hybrids have found their way into collections! Field marks: The yellow-throated vireo should be unmistakable, with its brilliant yellow throat and breast, only slightly less brilliant an the female than in the male, its olive-green back and its double, white wing bars. No other northern vireo is so brightly colored. It is much more deliberate in its movements than any of the warblers, less slender in form, and has a heavier bill. It looks something like a pine warbler, but this warbler frequents the pines, whereas this vireo is almost always seen in deciduous trees. Its color pattern is somewhat like that of the yellow-breasted chat, which is seldom seen away from dense thickets, is larger, and has a much longer tail; the behavior of these two is very different. The contralto voice of the yellowthroat will also distinguish it from other vireos.

Enemies: Probably the principal reason for the almost complete disappearance of this and other vireos from our New England urban and suburban districts has been the wholesale spraying of our shade trees. Ludlow Griscoin (1923) wrote of the New York City region: “Our handsomest Vireo was formerly a common summer resident throughout the area from early May to the middle of September. While many of us had noted a slow but steady decrease in numbers in the last 20 years, no one was prepared for the sudden and rapid disappearance of this species since 1917 over the whole suburban section, where it is now a rare bird.” And more recently Bagg and Eliot (1937) write: “In the early years of this century, the shade trees it so loved were persistently sprayed with poison for the elm beetle, gypsy moth, etc. Many Vireo-nests were ruined and many Yellow-breasts died from eating poisoned larvas. The bird became uncommon and has remained local.” It is hard to believe, and impossible to prove, that the birds, once so common here, have all perished from eating poisoned larvae; it seems likely that some have been forced to look elsewhere for their accustomed food, which they fail to find in their former foraging grounds; however, there are plenty of unsprayed trees, teeming with caterpillars and beetles, in all of our towns; but the vireos do not seem to have found them. There is some other reason, which we do not understand, that has caused the loss of this beautiful vireo.

Dr. Friedmann (1929) had reports of some 50 cases, from a number of different States, in which the yellow-throated vireo had been imposed upon by cowbirds, and says that the vireo occasionally buries the cowbird’s eggs in the lining of the nest, if it has no eggs of its own at the time. Edward R. Ford writes to me from Michigan: “I am reasonably certain that nests started after the first week in June were those of birds whose first attempt was unsuccessful, and that failure in the first instance was due to the cowbird. Of five successful nests, the last feeding of the young in the nest was observed May 31, June 8, July 15, July 23, and August 10, respectively. It will be noted that in three cases success was attained after the end of the cowbird’s laying cycle which, here, seems to be about July 1. The two low nests mentioned above were parasitized. One of these was deserted after two cowbird’s eggs had been removed; the other after the intrusion of two cowbird’s eggs and the ejection of one of the eggs of the vireo.”

Harold S. Peters (1936) mentions two external parasites, a louse, Myrsidea incerta (Kellogg), and a mite, Megninia tyrelli (Haller), that have been found on this vireo.

Fall: During the fall migration yellow-throated vireos wander about quite extensively and are likely to be seen almost anywhere that there are trees and in many places where they were not to be found during the breeding season. They sing more or less in September and are then more in evidence than the silent migrants. Their migration is evidently leisurely, for though most of them leave New England in September or earlier, Mr. Skutch tells me that he has not seen them in Costa Rica before October 20. Mr. Forbush (1929) says: “When the single brood has been raised the parents take them to the berry pastures and they pass the molting season amid the fruiting thickets and are ready for their long southward journey by September, if not before.”

Winter: Mr. Skutch writes to me: “The yellow-throated vireo winters throughout the length of Central America, from Guatemala to Panama, on both coasts and in the mountainous interior~up to an altitude of (rarely) 5,000 feet. It is at home in a variety of habitats, ranging from the heavy rain-forest to the low, thorny scrub and cacti of such arid regions as the middle Motagua Valley in Guatemala and the coast of El Salvador. In most parts of its wide and varied winter range it is far from abundant; but on February 1, 1935, I found it rather common in the arid scrub and low, open woodland near Cutuco, on the dry coast of El Salvador. Among the shade trees of the great coffee plantations on the Pacific slope of Guatemala, between 2,500 and 3,500 above sea level, I found it present during the winter months in somewhat greater numbers than in most parts of its Central American range: yet still far from common. These vireos do not form flocks; and one almost never sees two togethcr; but individuals may attach themselves loosely to mixed flocks of small birds.”

DISTRIBUTION
Range: Southern Canada to Colombia.

Breeding range: The yellow-throated vireo breeds north to southern Manitoba (Aweme and Hillside Beach, probably, and Winnipeg) southern Ontario (Kenora, possibly, South Magnatawan, Beaumarais, and Ottawa); southern Quebec (Pelissier, Montreal, and Hatley); and central Maine (Ripogenus, Dover-Foxcroft~ and Calais). East to Maine (Calais and Portland) ; the Atlantic Coast States to about central Florida (New Smyrna and Glencoc). South to Florida (New Smyrna, Oxford, Brooksville, and very rarely to Pensacola) ; southern Mississippi (Pearlington) ; southeastern Louisiana (New Orleans and Thibodaux) ; and central Texas (Houston and Kerrville). XVest to central Texas (Kerrville and Gainesville) ; eastern Oklahoma (Hartshorne, Tulsa, and Copan); eastern Kansas (Winfield, Topeka, and Manhattan) ; eastern Nebraska (IRed Cloud and Greeley) ; eastern South Dakota (Yankton and Sioux Falls); eastern North Dakota (Hankinson, Fargo, and the Turtle Mountains); and southern Manitoba (Aweme). From the records it appears that within the last generation the yellow-throated vireo has extended its range southward or at least has increased in members in the southern part of its breeding range.

Winter range: In winter the yellow-throated vireo is found north to southern Veracruz (TIes Zapotes and Santecomapam) ; Yucat~in (Chichen-Itz~); and Quintana Roo (Cozumnel Island). East to Quintana Roo (Cozumel Island and Chunyache) ; British Honduras (Toledo district) ; eastern Guatemala (Gualan) ; eastern Nicaragua (Blue6elds) ; Costa Rica (Guapiles) ; Panama (Boquete), and Colombia (Santa Marta district and Perico). South to Colombia (Perico and Santa Elena). West to Colombia (Santa Elena); Panama (Garachine) ; Costa Rica (San Jose and Liberia) ; western Guatemala (San Jos6 and Colombia); Chiapas (Huehuet~n); and Veracruz (Tres Zapotes).

Migration: Late dates of spring departure are: Panama: Barro Colorado, March 12. Costa Rica: Valley of El General, April 16. El Salvador: San Salvador, April 8. Guatemala: Moca, March 6. British Honduras: Mountain Cow, April 14. Mexico: Chiapas; San Benito, March 12. Cuba: Habana, April 11. Florida: Fort Myers, April 3.

Early dates of spring arrival are: Florida: Pensacola, March 11. Georgia: Beachton, March 19. South Carolina: Charleston, March 21. North Carolina: Statesville, March 27. Virginia: Lawrencevile, April 4. District of Columbia, Washington, April 1. Pennsylvania: Beaver, April 26. New York: Watertown, April 29. Massachusetts: Boston, May 4. Vermont: Wells River, May 2. New Hampshire: East Westmoreland, May 2. Louisiana: Thgolets, March 2. Tennessee, Memphis, March 28. Kentucky: Bowling Green, April 15. Illinois: Olney, April 18. Ohio: Columbus, April 18. Michigan: Ann Arbor, April 25. Ontario: London, May 5. Missouri: St. Louis, April 10. lowa: Keokuk, April 26. Wisconsin: Madison, April 29. Minnesota: Lanesboro, April 27. Texas: Kerrville, March 15. Kansas: Manhattan, April 22. North Dakota: Argusville, May 15.

Late dates of fall departure are: North Dakota: Fargo, September 6. Kansas: Lawrence, September 29. Texas: Fredericksburg, October 15. Minnesota: St. Paul, September 27. Wisconsin: New London, September 20. Iowa: National, October 3. Michigan: Detroit, September 23. Indiana: Notre Dame, October 11. Ontario-Guelph, October 10. Ohio-Youngstown, October 4. Kentucky: Danville, October 6. Tennessee: Nashville, October 7. Arkansas: Jonesboro, October 6. Mississippi: Ariel, October 14. Louisiana: New Orleans, October 11. New Hampshire: Jaih’ey, September 5. Massachusetts: Williamstown, September 20. New York: Rhinebeck, October 2. Pennsylvania: Harrisburg, October 4. North Carolina: Arden, October 10. South Carolina: Spartanburg, October 8. Georgia: Athens, October 14. Florida: Gainesville, November 12.

Early dates of fall arrival are: Florida: Pensacola, September 3. Cuba: Habana, August 31. Mexico-Yucat6n: Chichen Itz~, October 6; Oaxaca: Tepanatepec, October 27. Guatemala: Colomba, September 30. El Salvador: Divisadero, October 3. Nicaragua: Greytown, October 4. Costa Rica: San Jos6, October 4. Canal Zone: New Culebra, November 3.

Casual records: A specimen of the yellow-throated vireo was collected at Flatts, Bermuda, on March 24, 1931; another was collected in Nevada at Crystal Spring, Pahranagat Valley, Lincoln County, on May 29, 1932.

Egg dates: Arkansas: 3 records, April 24 to July 4.

Massachusetts: 19 records, May 16 to June 14; 14 records, May 30 to June 9, indicating the height of the season.

New York: 20 records, May 24 to June 30; 16 records, May 31 to June 14.