An association with species of live oak trees, and largely non-migratory habits distinguish the otherwise nondescript Hutton’s Vireo. Male and female Hutton’s Vireos look alike, and are also quite similar in appearance to Ruby-crowned Kinglets.
Nest parasitism by Brown-headed Cowbirds is quite common in vireos, and Hutton’s Vireos are parasitized, though more so in some areas than others. The oldest known Hutton’s Vireo was banded in northern California and was more than 6 years old.
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Description of the Hutton’s Vireo
The Hutton’s Vireo is a small vireo with greenish upperparts, white to pale olive underparts, two wing bars, and a nearly complete white eye ring and white lores. Length: 5 in. Wingspan: 8 in.
The Hutton’s Vireo is very similar to the Ruby-crowned Kinglet.
The sexes are similar.
Seasonal change in appearance
Juveniles are similar to adults but have buffy wing bars.
Hutton’s Vireos inhabit oak woodlands.
Hutton’s Vireos eat insects.
Hutton’s Vireos forage in trees and shrubs, sometimes hovering to reach prey.
Hutton’s Vireos are resident along the west coast of the U.S., as well as in parts of the southwestern U.S. and Mexico. The population is stable to increasing.
Bent Life History
Visit the Bent Life History for extensive additional information on the Hutton’s Vireo.
The shape of a bird’s wing is often an indication of its habits and behavior. Fast flying birds have long, pointed wings. Soaring birds have long, broad wings. Different songbirds will have a slightly different wing shape. Some species look so much alike (Empidonax flycatchers) that scientists sometimes use the length of specific feathers to confirm a species’ identification.
Wing images from the University of Puget Sound, Slater Museum of Natural History
The Hutton’s Vireo is mostly non-migratory, an unusual trait among North American vireos.
There are 8 named subspecies of Hutton’s Vireo in North America.
Calls include a nasal “ree-dee-dee”, while the song consists of a series of repeated whistled phrases.
The Ruby-crowned Kinglet has a smaller bill that is not hooked at the tip. Also smaller, more active.
The Gray Vireo is grayer overall than the Huttons, which has an olive tint on the back.
The Bell’s Vireo has a dark line through the eye.
The Hutton’s Vireo’s nest is a cup of bark shreds, moss, and other plant materials, is lined with grass, and is typically placed on a forked twig of an oak tree.
Number: Usually lay 4 eggs.
Color: White with darker markings.
Incubation and fledging:
The young hatch at about 14-16 days, and begin to fly in about another 2 weeks, though continuing to associate with the adults for some time.
Bent Life History of the Hutton’s 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 Hutton’s Vireo – the common name and sub-species reflect the nomenclature in use at the time the description was written.
VIREO HUTTONI HUTTONI Cassin
The typical form of Hutton’s vireo inhabits the Pacific slope, from Vancouver Island southward through Washington, Oregon, and California, west of the high Sierras, to about latitude 300 in northwestern Lower California. Two other races have been described from Vancouver Island and from Washington, but they are not now recognized on the A. 0. U. Check-list.
Throughout most of its range, it seems to be partial to the growths of the evergreen oaks, where it lives at all seasons. As Clark C. Van Fleet (1919) says: “One always associates the Hutton Vireo in his mind with the live oaks. I always think of this little fellow as the spirit of the live oak tree. The tree stationary, unconscious until livened by its spirit, in whose unfolding bosom the spirit lives and dies.”
Howard L. Cogswell writes to me: “This vireo is much less common in the Los Angeles area than farther north around Santa Barbara, where it is found at all times in every small canyon or oak region. In the Pasadena area there are five or six oak areas on the outskirts of the city in each of which one or two are found regularly. I have also seen Hutton’s in the broader mountain canyons in sycamore, maple, and oak associations, in the tall chaparral of Griffith Park, Los Angeles, and in the willow regions along the lowland streams.”
Grinnell and Storer (1924) write: “Four species of vireos or ‘greenlets’ are found in different portions of the Yosemite section during the summer months but only one, the Hutton Vireo, remains in the region through the winter as well. This vireo is almost exclusively an inhabitant of the live oaks and golden oaks and this choice of habitat is doubtless the basis for the continuance of the bird here during the winter months. These ‘evergeen’ oaks furnish forage in the form of insects throughout the year, as is shown by the number of warblers and kinglets which resort to these trees during the colder months. The Hutton Vireo, by being restricted to this type of tree, is assured of food in all seasons, and does not need to migrate.”
Ralph Hoffmann (1927) designates its habitat as “in the live oaks west of the Sierras and in young firs west of the Cascades.” Samuel F. Rathbun tells me that it is a resident throughout the year in western Washington, and “is most often to be found in or about the dense second growth of conifers that are of considerable size.”
Nesting: Mr. Van Fleet (1919) gives the following good account of the nesting habits of Hutton’s vireo in Sonoma County, Calif.:
About the first and second weeks in March home-buildIng Is begun. The site being properly chosen, both birds begin the task. The round, deep-cupped structure is built entirely of Spanish moss, the first strands being woven on both sides of the chosen crotch, with loose ends hanging down; as the building goes on these hanging ends are woven together at the bottom and the nest begins to take shape. As the structure progresses the moss that goes to build it becomes finer and finer and each strand is woven in with a weaving motion of the bill. When the nest will support the weight, each bird, after it has placed the material it has brought, pops in and works with feet and body to round out and cup the structure.
Most of the material for the nest is collected within a radius of 35 to 50 yards of the nest, but seldom in the Immediate vicinity of the site and never from the same tree. * * * Building progresses slowly or rapidly, as the weather permits. I noted one pair commence and complete a nest in about four days; normally a week, two, or even a greater length of time Is required on account of the frequent showers we have in March and April. Sometimes a few days elapse between the completion of the nest and the depositing of the first egg, but usually the female commences to lay and does so daily until the setting is complete. Incubation Is begun at once. * * * The nest is usually built back from some open or clear space. It is almost useless to look in the first fringe of trees about the clearing; usually the nest Is to be found in the second or third row of trees from the opening. The only exception I have ever noted was a nest In a live oak in the middle of an open pasture. Although the tree was fairly thick, the nest was deserted before an egg was laid. * * * The nest is placed from 7 to 25 feet up, and well out at the end of a branch, usually very well concealed. As a matter of fact unless discovered building, the nest is almost impossible to locate. On one occasion I discovered a nest by the fact that its occupant, presumably the male, was singing while on the nest. I judged this to be a rather uncommon occurrence. The nest blends so well with its surroundings that sometimes, even though I have formerly located the nest, I have had difficulty In locating it again.
All his nests but one were placed in live oaks; one “was located in a small live oak tree about seven feet from the ground. It would have been impossible to have seen it from any angle except directly above, unless led to it by the birds. Fronds of Spanish moss hung all about it, part of one frond being woven into one side of the nest. * * * An unusual nest was one located in a manzanita bush under a live oak.”
Though Hutton’s vireo may show a preference, in California at least, for the evergreen oaks as nesting sites, it also nests in some other trees, shrubs, or saplings. Mr. Dawson (1923) mentions a nest in a bay tree and two in willows. Grinnell and Linsdale (1936), at the Point Lobos Reserve, found two nests in ceanothus and two in pines, none over 7 feet from the ground.
Mrs. Wheelock (1904) says that “in the valleys and foothills of California the Hutton Vireo builds its nest among the branches of the scrub oaks.”
Thomas D. Burleigh (1930) found two nests in western Washington, one near Kirkland and one near Tacoma, both in Douglas firs; one was “35 feet from the ground at the outer end of a limb of a fir, and was built entirely and compactly of light green usuca moss, lined well with fine grasses”; the other was a similar nest and similarly located, 25 feet up. There is a set of eggs in my collection, taken by Henry W. Carriger near Sonoma, Calif., that came from a nest about 16 feet from the ground in a laurel; it was apparently of usual construction, but was said to have been lined with fine grasses, a few feathers, and a little hair.
Mr. Dawson (1923) gives the following good description of a Hutton’s vireo’s nest: “An example before me is a three-quarter sphere composed of sycamore down, and the familiar gray-green usnea (a lichen, of course, but we all call it ‘moss’) lashed together with cobwebs. The edges arc made fast to forking twigs of live oak, and are exquisitely rounded, while a convenient twig below supports the bottom of the nest in graceful security. The nesting hollow, almost as deep as it is wide, is daintily lined with the finest of dried grasses. Its dimensions are three inches in width by two and threequarters in depth, outside; and two and three-eighths in width by one and three-quarters in depth inside.”
Mr. Rathbun mentions in his notes a nest found by D. E. Brown, in Pierce County, Wash., that “was 6 feet above the ground and attached to the end of a somewhat drooping branch of a spirea.”
Eggs: T he Hutton’s virco’s set usually consists of four eggs, sometimes only three, and very rarely five. The usual shape is ovate, but some eggs are slightly more pointed and some a little more elongated. The shell is smooth but without gloss. They are pure white and rather sparingly marked with a few small spots or fine dots, mostly near the larger end, of dark or light browns, or reddish brown. Some eggs appear to be nearly spotless.
The measurements of 40 eggs average 18.0 by 13.2 millimeters; the eggs showing the four extremes measure 20.0 by 14.2, 17.0 by 12.5, and 17.5 by 12.0 millimeters.
Young: Mr. Van Fleet (1919) writes:
Incubation Is performed by both parents, and It Is during this period tbat they are most wary against th~ detection of their treasures. I have seen one bird dive into the nesting tree, make the change at the nest and the other bird leave, so rapidly, that it seemed as though but the one bird had entered and left the tree. * * * About two weeks after Incubation is started the nestlings are hatched and by the time the month is out they are ready to take their first trials of flight. The nestlings are fed by both parents during their stay in the nest. I watched four fledglings being fed for a period of about an hour; they were visited every five minutes on an average dnring this period. The nestlings were partially covered with feathers at the time and were keeping the parents very busy filling their hungry mouths.
Mrs. Wheelock (1904) says that the yo~Ing “are fed by regurgitation for five days and, after that, the food is usually reduced to pulp before being given to them. It consists almost entirely of small tree-worms, green and white, the latter sometimes seeming, by their whiteness, to be fruit worms. The intervals between feeding are unusually short, ranging from three minutes to half an hour.”
Plumages: According to Ridgway (1904) young Hutton’s vireos, in juvenal plumage, are “similar to adults, but much grayer olive above, under parts much paler (chin, throat, and chest very pale olivegrayish), and auricular and suborbital regions pale as throat, etc., thus reducing contrast with pale orbital ring and supraloral line.”
Young birds apparently have a partial postjuvenal molt, mainly in August, which involves the contour plumage and the wing coverts but not the rest of the wings nor the tail. The first winter plumage is practically indistinguishable from that of the adult. Adults have a complete postnuptial molt that sometimes begins at the end of July and may continue through September.
Food: Dr. Edward A. Chapin’s (1925) report on the food of the Hutton vireos is based on the study of 77 stomachs, only 70 of which contained enough food for use. Furthermore, none of these were collected in March, April, May, or November, and so the results are not as satisfactory as they might be. There was a preponderance of animal food, 98.23 percent, made up of insects and a few spiders, but none of the small mollusks usual with other vireos. Nearly 46 percent of the food consisted of bugs (Hemiptera), nearly half of them stink bugs. Caterpillars, moths, and butterflies made up nearly one-quarter of the total food; beetles 13.25 percent, of which 8.12 percent were the useful ladybird beetles and 2.75 percent weevils. Other insects were eaten in small quantities, but spiders were found in all stomachs, averaging 2.05 percent. These vireos seem to eat too many ladybird beetles and not enough caterpillars, to compare favorably with other vweos.
Professor Beal (1907), in his earlier report, mentions among the Hemiptera: “Assassin-bugs, leaf-bugs, stink-bugs, leaf-hoppers, jumping plant-lice, and bark scales.” In the somewhat less than 2 percent of the vegetable food, he adds: “One stomach contained a few seeds of elderberries, two contained those of poison oak, and these with a few galls and some rubbish make up the whole of this part of the food.”
Behavior: Hutton’s vireo is a quiet, modest, unobtrusive bird that must be sought for to be seen in its shady retreats, where its olivegreen plumage blends so well with the foliage that it is far from conspicuous and it is not sufficiently active to attract attention. Mr. Van Fleet (1919) describes its behavior very well as follows:
The Hutton Vlreo is not -a bird likely to draw attention to himself. There Is no fluttering of wings or hasty glances here and there for food, such as distinguishes the Kinglet; no hammering or pounding and gay chattering or scolding, in the manner of the Plain Titmouse. His sober mantle of olive green is not less subdued than his movement from branch to branch, and tree to tree, his quiet peering under leaves and bark scales, where he takes toll of the teeming insect life. Occasionally a large insect will fail his prey; he will then stop and diligently snip off the wings and legs before attempting to swaliow it. Rarely, he will dive forth from the protection of the trees at a passing insect, very much in the manner of a flycatcher; but on his return to the protection of the green foliage his flycatcher propensities desert him and he usually goes full tilt into the cover rather than show himself longer than necessary.
All observers agree that this, like most other vireos, is very tame and confiding, or rather fearless, as shown in its attachment to its nest. It is usually necessary to lift the bird of! its nest in order to see the eggs. Mr. Dawson (1923) mentions an extreme case, in which J. H. Bowles, in attempting to collect a set of eggs, “had been obliged to cut away a large willow branch, and the foliage was so heavy and so one-sided that the branch had turned over in his hands, insomuch that the Vireo’s nest, which hung near the tip, was nearly upset, lacking nearly an eighth turn, that is, a quarter of a half, of being upside down. But the bird clung to the nest, and it was her presence alone which saved the eggs! Even when the branch was hauled in, she required to be removed by hand. A large experience with this bird, unfolding with the years, shows it to be, without exception, the most confiding species within our borders.”
Under the name Anthony’s vireo, which is now discarded, Mr. Burleigh (1930) writes of its habits in northwestern Washington:
This little Virco may he fairly plentiful here hut It Is so quiet and inconspicuous that it is easily overlooked and may therefore he thought scarcer than It really Is. It is certainly unlike any of the other vireos with which I am familiar for I rarely heard it utter a sound, and during the spring it oddly enough became even more retiring and nothing even slightly resembling a song was heard. At Intervals throughout the winter single birds were seen feeding in underbrush In the short stretches of woods, frequently with restless flocks of Ringlets, but I soon realized that unless actually looked for they possibly would not have been noticed.”
Mr. Rathbun watched a pair of Hutton’s vireos during their nestbuilding activities for over an hour and witnessed a display of hostility by the hard-working female against her less active mate; he writes in his notes: “During the time occupied by this work the male sat near where first seen, and ceaselessly uttered his notes. As soon as the female had completed her work on the nest,. she flew directly at her mate, attacking him, and the birds for a moment struggled together, the male seeming to be rather on the defensive; then suddenly the female flew away closely followed by her mate. These actions on the part of both birds were repeated several times subsequently. Invariably, after the female finished her work on the nest, an attack on her mate would follow, the last seen being to all appearances the most vicious, for in this instance the birds fell to the ground in their struggles.”
Voice: If Hutton’s vireo is not a brilliant singer, it is certainly a persistent one, as shown by some song records sent to me by Mr. Rathbun, who watched one singing and being answered by another for a long period. He says that, at a distance, the note “sounds somewhat like tc/ter-t’ee, the first syllable being quickly given but prolonged and somewhat accented, the second with a rising inflection; and the repetition of this note or call was so rapid and so long continued that I timed the bird. I found that it was repeated at the rate per minute of ’61: 67: 62: 75: : 25-: 20–: 57: 71: a slight intermission and then 40, this representing a succession of minutes.” Several other somewhat similar records were made, sometimes in a higher and sometimes in a lower key, for periods of six consecutive minutes, the last of which was the most rapid and protracted of them all. “Following the lapse of seven minutes, the notes again began to be given in a slightly higher key. This record was per minute, 52: 78: 78—71: 7~–: 73: 71: 63: 69: ’11-: 66: 15, covering a time of eleven minutes and a few seconds. The total time of this was 675 seconds, during which the note was given 781 times, this proving a complete~Yecord or performance, as the bird was not again heard for quite a long time. When once more heard it was some distance away. These notes were given with much regularity and rapidly, and at times some were of less strength than at others, though all were clear. When quite close, the note sounds much like 8er-ree. During my stay both birds were quite often heard and seemed to be calling to each other.”
Mr. Cogswell writes to me: “Hutton’s ‘song is usually a repetition of two notes, the second either higher or lower than the first, with the accent on the higher note: chde: ckde: wedn, wedn, ieee, wee, etc., or chu: chu: etc.
When not singing, these vireos often give a simple, light kip, kip, kip call note, and this or their song is sometimes preceded by an odd mewing twittering. In addition, they give a nasal grating (scolding? note. Many times, though, a bird will sing repeatedly for as much as 15 or 20 minutes, and then become completely silent for as long a period or more.”
Mr. Van Fleet (1919) writes:
During the fall and winter this Vireo’s liquid note is seldom beard and then but a contented bar or two while feeding. But at the first breaking of winter into spring his notes become more frequent. The nuptial song is a constant repetition of a single note, often for a prolonged period. It is like the twanging of a bow string in one key, quid, quid, quid, repeated indefinitely. The above is not an attempt to reproduce the note, as it has more liquid quality and there is a slight cadence in it ranging higher towards the end of the note. In some individuals it is given a slight trill like water over stones. The earliest I have heard their song, if song it could be called, is in the first week of February, and It Is to be heard from then on until late summer.”
Other published accounts of the vocal efforts of Hutton’s vireo do not differ greatly from the above descriptions, but Ralph Hoffmann (1927) adds that “it has besides a tsckule t8chuk uttered in a low lnquiring tone, and a low whit whit.”
Field marks: Hutton’s vireo is a small vireo, but not the smallest; it is smaller than Cassin’s or the western warbling vireo, but larger than the least vireo. It is the greenest of all the Pacific coast vireos. It has a prominent eye, with an incomplete white eye ring, set in a rather large round head, and has two faint white wing bars. It might easily be mistaken for a female ruby-crowned kinglet, with which it is often associated in winter, but it is larger, has a st.outer bill, its movements are more deliberate, with less flicking of the wings, and its notes are entirely different.
Enemies: Mr. Van Fleet (1919) says that “as the nest is strongly anchored to green wood and deeply cupped the danger of accident or disease is’~izeduced to a minimum. The nests are invariably so well concealed that a marauding jay or squirrel has little chance of discovering it, unless by accident. In fact I have never found but one raided nest.” But the dwarf cowbird succeeds in finding it occasionally.
Winter: iHutton’s vireo is resident all winter throughout practically all of its breeding range, in its usual haunts among the evergreen oaks and some of the conifers, firs in the north and pines and cypresses in the south. At that season, it is often found associated with kinglets, various warblers, bushtits, chickadees, and other small birds that frequent such localities. It is often heard singing during the latter part of February.
Range: From southwestern British Columbia to central Mexico; not definitely migratory.
Breeding range: The Hutton’s vireo breeds north to southwestern British Columbia (San Josef, Vancouver Island; Kingcome Inlet and Chilliwack, possibly); northwestern Washington (Bellingham and Tacoma) ; western Oregon (Portland) ; through the interior of California (Baird, Grass Valley, and Big Creek) ; southeastern Arizona (Santa Catalina Mountains, Graham Mountains, and Chiricahua Mountains); extreme southwestern New Mexico (Cloverdale and the Animas Mountains); and southwestern Texas (Chisos Mountains). East to southwestern Texas (Chisos Mountains) ; Coahuila (Diamente Pass) ; and Tamaulipas (Miquihuana). South to Tamaulipas (Miquihuana), Durango (El Salto); Sinaloa (mountains south of Babizos); and the Cape region of Lower California (Miraflores). West to Lower California (Miraflores, Victoria Mountains, San Ram6n, and Ensenada) ; the coastal region of California (Escondido; Santa Catalina, San Rosa, and Santa Cruz Islands; Santa Barbara, Santa Cruz, Oakland, and Eureka) ; western Oregon (Grants Pass and Coos Bay); western Washington (Ozette Lake); and Vancouver Island, British Columbia (Victoria and San Josef).
The range as outlined includes all the North American races of the Hutton~s vireo, of which four are recognized. The Vancouver vireo (V. A. insularis) is found on Vancouver Island and possibly the adjacent mainland; the typical race (V. A. hutto’ni) breeds west of the Cascades in Washington and Oregon and west of the Sierras in .California to about latitude 300 in northwestern Baja California; Stephens’s vireo (V. A. stepAen~si) breeds from southeastern Arizona to southwestern Texas, south to northern Nayarit and Tamaulipas; Frazar’s vireo (V. A. cognatus) breeds in the Cape district of Lower California. Other races are resident in Mexico and Central America.
Though there seems to be some seasonal movement of individual Hutton~s vireos, no definite migratory movement can be distinguished.
Egg dates: Arizona: 10 records, May 10 to June 24; 6 records, May 28 to June 9.
California: 57 records, February 22 to June 20; 24 records, April 24 to May 26, indicating the height of the season.
Washington: 12 records, May 2 to June 26; 9 records, June 4 to 2~.
Lower California: 1 record, May 10.
VIREO HUTTONI STEPHENSI Brewster
This pale southwestern subspecies is found in southern Arizona, New Mexico, central western Texas, and southward to Tamaulipas and the northern part of the Mexican Plateau during the breeding season at least.
William Brewster (1882) described this race and named it in honor of Frank Stephens, who collected and sent him a series of five specimens including the type. The wing of stephensi is decidedly longer than that of typical huttoni and its coloration is much lighter and duller. In comparing the two races, he states that whereas huttoi&i is “olive-green above and olivaceous-yellowish beneath,” with “no clear white anywhere”; stephensi is “grayish-ash above with no decided olive-green excepting on the rump and tail. Beneath brownishwhite, untinged with yellowish excepting on the sides and crissum. Wing-bands pure white and nearly confluent.”
Mr. Stephens found it “not uncommon in scrub-oaks” (Brewster, 1882) in the Chiricahua and Santa Rita Mountains in Arizona, and near Fort Bayard in New Mexico, where it seemed to be confined to the mountain ranges. Mrs. Bailey (1928) reports it in the Animas Mountains, N. Mex., from 5,800 to 8,100 feet.
Harry S. Swarth (1904) says of its status in another range of Arizona mountains Possibly this species remains in the Hunchucas [sic] Mountains throughout the winter, but I am inclined to doubt it, and if it does it must be in very limited numbers. I secured a single bird as early as February 20th, but no more were seen until March 2nd, when another was taken; about the middle of March they became more abundant, though not a common bird at any time, and soon after the middle of the mouth were already in pairs. Upon their first arrival they were found mostly in the live oaks near the base of the mountains, but the breeding range seems to lie between 5000 and 7500 feet. During the breeding season these vireos were very quiet and inconspicuous, and were most easily overlooked; but after the middle of August they began to appear in considerable numbers, and were more nbundant at this time than at any other.
In Brewster County, Tex., Van Tyne and Sutton (1937) “found the Stephens’ Vireo fairly common in the Chisos Mountains above 6400 feet.” In the same mountains, Herbert Brandt (1940) heard this vireo singing “in a canyon-floor oak grove, * * * nearly erect on a dead limb.” Based on a small series of specimens in fresh plumage, he gave the birds of this region a new name, Vireo huttoni carolinae, in honor of his wife; Dr. Oberholser had told him that they “proved much darker above and rather darker below” than typical stephen,si from farther west.
Nesting: Frank C. Willard (1908) saw a pair of Stephens’s vireos building a nest in “a scattering growth of oak brush” on a steep hillside in the Huachuca Mountains, Ariz. He says:
The female was evidently using some cobweb. After it was placed to her satisfaction the male took a turn at re-arranging it. During all the time I watched him he did this and several times he brought material which he invariably dropped, none of it ever finding its way into the nest. On June 5 the female was sitting. She did not leave the nest until touched. * * * The nest Is a wonderful piece of bird architecture. it is composed of a frame work of fine grass holding together a thick mat of oak down almost as compact as felt. The prongs of the fork are entirely covered with the down held on by cobwebs. There is a scanty lining of fine grass tops. As is the case with the Plumbeous, the seeds are all removed from the grass tops used In the lining. The nest has a yellowish appearance. * * * On June 10th an intruding Jay helped me locate a nest with three wellfeathered young. The nest was in Carr Canyon and was placed at the top of a black oak sapling growing out of the side of the canyon. The nest was fifteen feet from the ground and seventy-five from the bed of the canyon which is very deep with precipitous walls. The male came with a caterpillar but seeing me would not go to the nest The female, however, fed the young and brooded them without paying much attention to me. * ï * On May 22 another bird was seen building, the nest being almost completed, apparently. June 3rd no bird was around and June 12th, when I again visited it, the nest had entirely disappeared. Not a vestige was left. I climbed up to examine the fork where It had been and it was cleaned off completely.
Mr. Willard and I had a similar experience in 1922. On May 1 we saw a pair of Stephens’s vireos building a nest about 6 feet up in a clump of oak saplings in the lower part of Ramsay Canyon in the Huachucas. We did not go near it, for fear of frightening them away and remembering his previous experience with these shy birds. But our caution was of no avail, for, when we visited the spot on May 10, the nest had so completely disappeared that we could not even find a trace of it; evidently the birds had entirely removed it after they learned that we had discovered their secret.
There are three beautiful nests of this vireo in the Thayer collection in Cambridge that were taken in the Chiricahua Mountains, Ariz. The first, taken by Virgil W. Owen on May 28, 1906, was attached to a horizontal crotch in the topmost branches of an ash tree on the bank of a mountain stream, 16 feet above the water and well-concealed in the new foliage. The second was also taken by Mr. Owen, on June 2, 1906; it was “18 feet up and near the top of a slender olive oak tree which was growing near a stream”; it is suspended between small twigs close to a vertical branch and was apparently well shaded by a spray of leaves just above it, which are still attached to the branch; this is the largest of the three nests, measuring externally 3 by 2½ inches in diameter and nearly 3 inches in height; the internal diameter at the top is about 1½ inches, but it is much wider within, as the rim is much incurved; the inner cup is nearly 2 inches deep. The third nest, taken by H. H. Kimball on June 24, 1908, was 15 feet from the ground, attached to some small twigs under a crotch of a sycamore limb. All these nests were more or less well-concealed in the foliage, much of which came with the nests.
The nests are all alike in general appearance, looking like cupshaped, yellowish-buff sponges, quite different from any vireos’ nests that I have ever seen. At first glance they appear to be made entirely of this yelloxvish-buff down, so completely and profusely are they covered with it, even enclosing the supporting twigs; the down probably was gathered from oaks, but perhaps from sycamores. But, on close inspection, it appears that this material is strongly reinforced with fine grasses, lichens, and a few green leaves, the whole being firmly bound together with spider silk. The lining consists of very fine yellow grass tops. Altogether, they are works of art.
In the Chisos Mountains in Texas, Van Tyne and Sutton (1937) saw a pair of Stephens’s vireos building a nest that “was swung from a clump of mistletoe which grew in an oak, and was about twelve feet from the ground.”
There is a set of three eggs in my collection, taken by Frank B. Armstrong in Tamaulipas, Mexico, on April 18, 1908, from a “nest of fine hay, hair, bark, cobxvebs and lichens, suspended from a limb 4 feet high in a thicket.”
Eggs: The usual set for Stephens’s vireo is three or four eggs, perhaps rarely five. They seem to be indistinguishable from those of Hutton’s vireo. Those that I have seen are sparingly marked with very dark brown or blackish, but others have mentioned markings in lighter shades of brown. The measurements of 25 eggs average 18.1 by 13.6 millimeters; the eggs showing the four extremes measure 19.5 by 13.6, 17.5 by 14.5, 16.9 by 13.6, and 18.2 by 13.2 millimeters.
Plumages: The molts and plumages are apparently in the same sequence as those of the species elsewhere. Van Tyne and Sutton (1937) say that a male in juvenal plumage, collected on July 18, “is paler and browner above than the adult, with broad edgings of bright yellowish green on the outer webs of the flight feathers. The throat is much like that of the adult, but the belly is whiter in the center and more buffy on the sides.” Mr. Swarth (1904) says:
Specimens taken the middle of August are In the midst of the moult, but some secured the first week in September have nearly completed the change. Birds taken at this time are generally rather darker and more olivaceous than spring specimens, with more greenish-yellow on the edges of the wing and tail feathers. Aside from these seasonal differences the series of specimens I secured here shows very little variation in color, and I took none which approach huttoni very closely; but I have a male specimen of huttoni taken at Los Angeles on December 6th, 1898, which is almost indistinguishable from autumnal examples of 8tephen.ei; being quite as pale in coloration, but having rather more greenish-yellow streakings on the sides and flanks than Is the case with that race. The bill is also of the larger size which distinguishes the coast race.
VIREO HUTTONI COGNATUS Ridgway
This is another pale race that is resident in the Cape San Lucas district of Lower California. Mr. Ridgway (1904) describes it as “similar to V. h. etep1iens~, but wing averaging decidedly shorter, tarsus longer, and coloration paler. Adults with olive-gray of upper parts slightly paler and greenish olive of rump and upper tail-coverts much less pronounced, under parts whiter, the chest, etc; much less strongly tinged with olive-buff. Young with under tail-coverts, anal region and lower abdomen much less strongly tinged with buff.”
William Brewster (1902) remarks that “Lower California specimens of Stephens’s Virco have larger bills than those from Arizona, but I can discover no other differences.” His specimens were collected by M. Abbott Frazar, for whom the subspecies was named. He says of its haunts:
Mr. Belding, who was the first to detect Stephens’s Vireo in Lower California, gives It in his list of mountain birds as “common above 3,000 feet altitude,” but “not observed below this.” Mr. Frazar found it numerous among the pines on the Sierra de Ia Laguna in May and early June, but none of the specimens killed there showed any signs of breeding. He also met with it at San Jose del Rancho in July, although not in any numbers. During his second visit to La Laguna, the last week of November, two birds were shot and several others seen on the very summit of this mountain, and a few days later (on December 2) a single specimen was taken at Triunfo, indicating that at least a few individuals winter in the Cape Region, to the northward of which, on the Peninsula, this Vireo has not yet been noted.
Nesting: Not much is known about the nesting habits of Frazar’s virco. J. Stuart Rowley seems to be the only one that has seen its nest He says in his notes: “On May 10, 1933, on the sierra above Miraflores, while I was eating lunch in the shade of some trees, a dull green bird flashed before me and without a sound flew directly to a nest not 20 feet from me and started brooding. All that was visible from where I sat was the basket nest with a large black eye peering over the edge at me and watching my every move. Upon approaching, the female silently flushed from the three eggs, which were slightly incubated. This was the only nest of this species I found; in fact, it was the only instance of observing these birds which I had throughout the whole Cape region.”
In response to my request for further information, Mr. Rowley writes to me: “Not being a botanist, I am not certain as to the species of trees in the area where this nest was located, but the prevailing cover here was oak, a small, scrubby form, and it was in this type of tree that the vireo nest was located. The surroundings were typical Sierra de la Laguna canyon country, being dry, rather steeply sloping country, full of flora which has thorns and continually raises the very devil with one’s clothes. The nest itself was made of small fibres and soft downy material, with a predominant covering of a local lichen, abundant in the oaks, so that the nest was cleverly and well concealed among the leaves.”
Charles E. Doe, who now has this set of eggs, probably with the original data, tells me that the nest was pendent in the fork of a low, thorny oak, about 4 feet from the ground; it measured 3 inches across the top and was 2 inches deep. He describes the eggs as “pure, dull white, faintly dotted at the larger end with almost black, brown dots.” They measure 0.78 by 0.55, 0.76 by 0.54, and 0.72 by 0.56 inch, or 19.7 by 14.0, 19.3 by 13.7, and 18.3 by 14.3 millimeters.