At least in parts of its range, the Gray Vireo can survive without drinking water. It occupies very hot and dry habitats of the southwestern U.S. and Mexico. The Gray Vireo is thought to migrate at night, but little is known about its migration.
The male Gray Vireo sometimes builds a shoddy nest at the same time that his mate is building the nest that she will actually use for nesting. Gray Vireo nests are sometimes parasitized by Brown-headed Cowbirds, but the nests are often abandoned when that happens.
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Description of the Gray Vireo
The Gray Vireo lives up to its name, being medium gray above, whitish or pale gray below, with one weak white wing bar on gray wings, a white eye ring, and white lores. Length: 5 in. Wingspan: 8 in.
The sexes are similar.
Seasonal change in appearance
Juveniles are similar to adults.
Gray Vireos inhabit brushy foothills and scrubby woodlands.
Gray Vireos eat insects and fruits.
Gray Vireos forage actively and low to the ground.
Gray Vireos breed across the southwestern U.S. and southern Great Basin. They winter in the far southwestern U.S. and in Mexico. The population appears to have increased overall, but declined in some areas.
Bent Life History
Visit the Bent Life History for extensive additional information on the Gray Vireo.
Gray Vireos are often quite tame when approached by birders.
Gray Vireos defend winter territories as well as breeding territories.
Calls include a sharp “chick” or a descending whistle, while the song consists of a rapid series of sweet notes.
- Plumbeous Vireo
The Plumbeous Vireo has bolder white eye markings and a shorter tail.
The Gray Vireo’s nest is a cup of weeds, stems, and bark shreds, is lined with softer materials, and is placed on a forked twig of a shrub.
Number: Usually lay 4 eggs.
Color: Pinkish-white with darker markings.
Incubation and fledging:
The young hatch at about 13-14 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 Gray 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 Gray Vireo – the common name and sub-species reflect the nomenclature in use at the time the description was written.
VIREO VICINOR Coues
Parched and barren foothills of the higher mountains baking in the searing heat of the interior of southern California: such is the favorite haunt of the gray vireo. Camped near the upper edge of the shelf rising sharply in some 3 or 4 miles from the floor of the Mohave Desert to the almost sheer-rising massive wall of the San Gorgonio Mountains, I arose one frigid May 18 when the thermometer was most certainly in the low forties if not in the thirties and started in pursuit of what was obviously a gray vireo singing joyously nearby. Cold or heat, it seemed to matter little. A few minutes of quiet trailing with the inevitable tantalizing fleeting glimpses were finally rewarded: the bird appeared on the outside of a bush and greeted me with the full benefit of his song, which was rendered even more superb by the unusual setting. I have spent far more time chasing down a Canada warbler deeply entrenched in a boggy forest in the East, as well as many others of our eastern forest dwellers, and can but wonder whether the well-known elusiveness of the gray vireo is not merely a matter of comparison with other western species in a country where low, dense foliage is comparatively lacking.
Other gray vireos were singing in the vicinity. The terrain was a dry wash several hundred feet above the Mohave and within perhaps a mile of the mountain bulwark. Juniper and cholla cactus were the most common forms of vegetation. Other birds in the inundate vicinity were western gnatcatchers. Lawrence’s goldfinches, and desert and black-chinned sparrows. Unpleasantly, if not significantly, a good-sized rattlesnake turned up altogether too near our sleeping spot.
Grinnell and Swarth (1913) limit the distribution of the gray vireo in the San Jacinto region of southern California to the “Adenostoma minor association, of the Chaparral major association, of the San Diegan faunal division, of the Upper Sonoran Zone,” chiefly on the Pacific side of the mountain. They found the species between about 3,000 and 6,500 feet altitude. On one occasion the species was among pinyons. Of primary importance, they bring out the fact that being preeminently an inhabitant of dry chaparral the species conflicts with no other member of the genus. On one occasion this species, the western warbling vireo, and the Cassin vireo were all heard simultaneously. “The notes of the latter two, however, resounded respectively from the alder-lined ravine bottoms, and from the golden or black oaks of the cool slopes, while the gray vireo sang from the chamissal on the hot, steep slopes.” Likewise, they heard both the Hutton’s and the gray vireos from the same stand, “the former, however, from the golden oaks, the latter, as usual, from the brush belt adjacent.” To make representation in the genus complete as far as normal distribution is concerned, they also found both the gray and the least vireos in one short stretch, “the former in some chamissal straggling down the west wall to the lowest limit of its range, the latter species in some guatemote and chilopsos along the stream bed.” They summarize the relationships of the various members of the genus as follows: “The presence of no less than five closely related species of one family in so limited a region is obviously closely dependent upon the separate, sharp, associational and zonal preferments of each. The warbling, Cassin and Hutton vireos are arboreal foragers; the least and gray vireos brush foragers; but the least is riparian, while the gray is distinctly a dry-slope forager.” They conclude that the gray vireo “has only been able to find its way into the avifauna of southern California from a Sonoran center of dispersal, through the existence of an associational niche not occupied by another vireo.”
Grinnell (1922) found an adult pair on the west slope of Walker Pass in northeastern Kern County, Calif., on July 25, 1922. The location was at an altitude close to 4,500 feet on a steep, north-facing hillside, Upper Sonoran Life Zone, but in a semiarid phase of it. “The birds were in sparse brush (Garrya, Ku~n.sia, Artemi8ia tridentata, and Cercocarpus betulaef olius) ; and a digger pine and a pinyon both grew within one hundred feet of where they were discovered.”
W. E. D. Scott (1885) took a specimen in Arizona on April 1 “in a pretty rolling grass country, where the trees are rather scattered, and at an altitude of 3500 feet.” He says further:
On the San Pedro River foothills of Las Sierras de Santa Catalina, at an altitude ranging from 2800 feet to 4000 feet (which is here the point of meeting of the mesquite timber and the evergreen oaks), [the species] is, excepting the Least Vlreo (Vireo pussUw~), the commonest form of Vlreo, being fairly abundant. ï * * The two altitudes mentioned seem to be about the limits of the species while breeding, an(i most of the birds secured were obtained between 8000 and 3500 feet altitude. * * The locality where the species is most abundant is where the mesquites terminate and the oaks begin; there being of course a sort of gradual transition and no well or clearly defined line, the two forms of trees being mingled about equally, I have found that the smooth flat mesas, and the broad open bottoms of the wider cafion are quite as much frequented by them as the rough and broken hillsides, and It Is difficult to ride about anywhere between the altitudes above mentioned, without hearing the very characteristic song of the species.
It is interesting to note that on June 26 he did find one bird well up within the oak belt.
Nesting: Grinnell and Swarth (1913) found a nest in the upper tangle of a greasewood (Adenostoma fas-ciculatum). This nest was 33 inches from the ground, which was sloping, and was discernible for several yards though well surrounded by the sparsely leaved greasewood twigs. Another nest, also found on the same date, May 21, in the same kind of a bush, was 36 inches above the ground. The nests are “similar to other vireo’s nests in shape and semi-pensile attachment. The main support is at the rims, but their situation among the close-set, obliquely upright, stiffish stems of the greasewood afforded some support by minor twigs.” They give details as follows:
The measurements of the nests are, respectively, of each of the two nests in each respect: outside diameter, about 76, 73 mm.; inside diameter, 48, 47; outside depth, 54, 59; inside depth, 41, 43. The nests are composed largely of silvery gray weathered grass and plant fibers, usually with the vascular bundles unraveled. Some of these elements were evidently grass blades, some stems of plants, and others the shredded bark of weed-stalks. There is an admixture of tenacious spider-web, and portions of spider cocoons; on the very outside, In both cases, are many unbroken, tridentate, gray leaves of the sagebrush. Internally the nests are lined with a distinct layer of slender, disintegrated, hairlike fibers of great length, so that the inner surfaces of the nests are firm and smooth, but porous.
Florence M. Bailey (1928) describes New Mexico nests as being “in thorny bushes or trees, 4 to 6 feet from the ground, occasionally supported underneath or on sides; made sometimes of mesquite bark and loosely woven coarse grass, lined with fine grass, but also made of plant fibers, spider web, and cocoons, lined with long vegetable fibers and decorated with sagebrush leaves.” She describes, however (1904), a nest found in junipers at Montoya, northeastern New Mexico, which was composed “principally of shreds of bark, apparently the soft juniper hark, and, unlike ordinary vireo nests, was unadorned.”
W. E. D. Scott (1885) found a number of nests in Arizona of which one was “about seven feet from the ground, in smooth, flat country, at an altitude of about 3500 feet.” Another nest was built near the center of a mesquite and was about 6 feet from the ground in an upright V formed by two upright limbs. Although admitting that the rim of the nest was attached for almost half an inch of its circumference to a small twig on one side, and for an inch to another twig on the other side, he states: “The bottom of the nest outside does not quite rest in the angle of the V, but the sides rest firmly against the limbs forming it, and the result is a Vireo’s nest resting in a crotch, and in no degree pensile.”
Yet another nest he describes as: built In a kind of thorn hush, almost at the extremity of one of the upper and overhanging branches, six feet from the ground. It is composed externally of the dry outside skin or bark of a coarse kind of grass, rather loosely woven. But immediately beneath this loose, external layer is a wall of the same material, very closely and strongly woven. The lining of the nest, which is very distinct from the walls, extends throughout the interior. It is much thicker on the bottom of the structure, but extends up to the rim, where, however, it is thin. It is composed of fine dry grasses, arranged on the sides of the nest in concentric layers, much as the horsebairs are placed in the nest of Spizeila domestica. On the bottom this arrangement does not obtain, but the grasses cross one another seemingly at random, forming a soft mat. The walls are uniformly about one-fourth of an inch in thickness, and the shape of the entire structure is that of a half sphere. The external diameter at the rim is two and three-fourths inches, and the diameter at the same point inside is two and one-quarter inches. The depth outside is two inches, and inside one inch and three-quarters. The nest is attached at the rim for almost the entire circumference very much like a Red-eyed Vireo’s nest, hut here the resemblance ceases, for it Is not fastened to the many small twigs, on which it rests, that pass diagonally downward, so that it is not even a semi-pensile structure. The thorns of the bush, which are from an Inch and a half to two inches long and very sharp, protect the nest in every direction, for the whole Is entirely surrounded by twigs and small branches lie states further: “The structure is, as a whole, very symmetrical, but is widely different from that of other Vireos which breed in the neighborhood.”
James Murdock, of Glendale, Calif., in a letter to Mr. Bent, states that the nests he has found have usually been small and without any colors that stand out against the background; the spot is, therefore, quite difficult to see. He says that on one occasion he found the nest “only after watching the bird hop repeatedly from branch to branch in the chaparral, always seemingly following the same routine. This bird usually entered from the left side of the tree and progressed by hopping from branch to branch around the outside of the bush facing me and then by going through the bush back nearly to the spot at which it first perched. I found the nest near this location.”
Wilson C. Hanna writes to Mr. Bent: “My notes record 13 nests, and these have been between 2½ feet and 8 feet from the ground, averaging 4 feet. The host shrubs have been about equally divided between big sagebrush (Arternisici tridentata) , antelopoe-brush (Purskia glandulosa), and greasewood chamise (Adenoatorna fascioula-. turn), and a single nest each in mountain-mahogany (Cercocarpu.s betulciefolius) and pinyon (Pinus monophylla) .”
Eggs: Scott (1885) discovered a nest in Arizona on May 26 which was apparently finished, with the female sitting very close. He says: “Daily visits to the spot showed the same circumstances obtaining until May 30, when the first egg was laid; and then an egg was laid daily until June 2, when the laying was completed, four eggs being in this case the full set.” He says further that the eggs are “rather rounded in general shape, though one end is somewhat sharper than the other. The ground-color is rosy when fresh, becoming a dead white when blown, rather sparsely spotted with irregularly shaped dark umber brown dots, chiefly at the larger end.” With one egg broken, he gives the measurements of the others as “.77 x .59, .78 x .58, and .75 x .57 inches.” Another nest found on June 6 “contained three slightly incubated eggs, which do not vary in color from those already described, except that the spots are of a slightly redder brown, and they are more concentrated at the larger end. The eggs are rather smaller and even more rounded in general shape than the other set spoken of, being but little more pointed at one end than at the other. They measure .72 x 58, .70 x .55, and .68 x .53 inches, respectively.”
Grinnell and Swarth (1913) describe the eggs as “pure white in color, with numerous abruptly-defined minute dots and spots of not more than one-half millimeter diameter, nearly all agglomerated around the large ends. In color these markings are mostly very dark, of clove brown and sepia tones; a few approach drab. The eggs measure: no. 74: 18.3 x 14.5, 18.7 x 14.0, 18.8 x 14.1; no. 75: 17.8 x 14.7, 17.8 x 14.6, 18.2 x 14.7.”
Frank Stephens (1890) gives measurements as 0.73 by 0.57, 0.74 by 0.55, 0.74 by 0.55, and 0.77 by 0.53 inch, with color similar to those described by Scott.
The measurements of 31 other eggs average 18.0 by 13.5 millimeters; the eggs showing the four extremes measure 19.7 by 13.9, 18.6 by 14.6, 17.2 by 12.4, and 17.7 by 12.2 millimeters.
Young: Florence M. Bailey (1904) found a nest with three newly hatched young at Montoya, N. Mex., on June 15. But W. E. D. Scott (1885) in Arizona found fully fledged young shifting for themselves on June 4 and on the same day “found a pair of these birds just starting to build: but this was the second brooding, as the female of the pair, which I took before I discovered the nest, clearly showed.” Again, he took on May 26 “two young males that had just left the nest and were under the care of the male parent bird.”
Coues (1878) says of the young: “A specimen just from the nest is brownish-gray above, white below, without a trace of olivaceous or yellowish on the body; the quills and tail-feathers have yellowisholive edgings, rather stronger than in the adult, and there is a slight whitish bar across the ends of the greater coverts. The bird bears a superficial resemblance to a small faded specimen of V. plumleu.s, but is quite different.”
Ridgway (1904) says: “Texture of plumage looser and much softer than in adults; coloration similar, but the gray of upper parts slightly more brownish, white of under parts purer, and pale edgings to remiges and rectrices and tips of greater coverts tinged with pale olive.”
Plumages: W. E. D. Scott (1885) says of his series of 42 males and 12 females, all of which except one were taken between April 1 and June 11, “They present very little variation in size or color, and the young in first plumage do not differ materially from the adult birds.”
Frank Stephens (1890) considers the California birds different from those east of the Colorado River in breeding area. He says: “The most prominent difference between the two forms is the darker color. above, combined with the greater amount of whitish edging on wing and tail, in the California form.”
Grinnell (1922) collected a male out of a pair at Walker Pass, Kern County, Calif., on July 25, 1922. lIe says that the bird “proved to be in molt, with only two of the old tail-feathers remaining and with new feathers showing where old ones had fallen out, in the wings and in most of the body tracts. The weight of the bird was 12.5 grams.”
Grinnell and Swarth (1913) describe an adult male secured on August 27 as being in nearly full fresh fall plumage. “The annual molt is very nearly completed, only the outermost primaries being still partly unsheathed.” They say further:
Since there is in all probability no spring molt, even partial, this bird presents the true color characters of the species. As compared with the better known spring plumage, conspicuous among various species of the family for its general plumbeous tone, the freshly acquired plumage is not so distinctly gray save about the head. The whole dorsum, the outer surface of closed wing, and, more appreciably, the rump and upper tail coverts, are pervaded with a tinge of green; the sides and flanks have a conspicuous tinge or mixture of primrose yellow; and there is a faint huffy suffusion across the chest All these tints are evidently very much reduced, or obliterated altogether, through the intervening months of wear and fading, until spring brings the notable gray cast again.
With more material than had been available to Frank Stephens, they came to the conclusion there was no basis for systematic separation of the California birds from the Arizona ones. They conclude, in this respect, as follows: “From a consideration of its distribution as now known, it appears probable that the gray vireo has invaded California from the south-central plateau region of western North America, within relatively recent times.”
Food: Frank Stephens (1878) comments as follows: “I have never seen them catching insects in the air, as some other Vireos do, but have observed them scratching on the ground like a Pipilo.”
From the only two stomachs examined by the Biological Survey, Dr. Edward A. Chapin (1925) could obtain only a hint as to the food of the gray vireo: “Caterpillars and a small moth were found in one stomach, together with a stink-bug (Prionosoma podopioides), a tree hopper (Platycentrus acuticornis), and a tree cricket (Qecanthus). In the other stomach two dobson flies (Cihauliodes), a small cicada (TThicinoides he8peri us) , and a long-horned grasshopper made up the greater part of the contents; two beetles (Acmaeodera neglecta and Pachyln’ackys) complete the list.”
Behavior: Grinnell and Swarth (1913) found the species a constant accompaniment of the belts of the two species of chaparral bushes, Adenoetoma sparsifolium and A. fasciculatum. They say: “While adhering closely to the cover of these plants, it foraged also through scrub oak, manzanita, and ceanothus, occasionally into four-leafed pifion (Pinus parryana) or sagebrush (Artenvisia tridentata). The forage depth of this vireo is between one and five feet above the ground, rarely any higher. A person may follow a bird around for twenty minutes, keeping track of it by the oft-repeated song, without catching a view of it above the level of the chaparral tops.”
Grinnell (1922) witnessed a particularly interesting variation from the foregoing of which he writes as follows: “From the bushes she went into the pinyon tree before mentioned, and thence into the digger pine, reaching the unusual height of some fifteen feet above the slope at the base of the tree. Her head was turned from side to side at frequent intervals, especially when she approached and eyed me curiously at a range of not more than 12 feet.” He also brought out the fact that most of the time the tail drooped below the axis line of the body.
H. W. Henshaw (18Th), finding adults with fledged young on July 8, says: “The parents manifested the utmost solicitude, and flew to meet me, uttering a variety of notes, now flying to the edge of the thicket, and remonstrating with me with harsh cries of anger and alarm, now returning to their young, and with earnest warning notes endeavoring to lead them away from a spot which to them seemed fraught with danger.” The young were still dependent on the old for food.
W. E. D. Scott (1885) on May 26 found a “female sitting on the nest, and the male singing in the bushes close at hand. The female was very tame, and in order to see the interior of the nest I was obliged to touch her with my fingers before she would leave her home. Several times afterwards, in watching the progress of laying, I was obliged to repeat this action, and once had to lift thebiid out of the nest.”
J. Van Tyne and G. M. Sutton (1937) collected a pair in Brewster County, Tex., and commented on three birds seen about “the habit of flicking their long tail nervously as the gnatcatcher does.”
A. S. van Rossem (1932) speaks of the bird as “far from typical of the family in habits for its quick, jerky movements and cocked-up tail led us more than once to mistake it. for a wren.”
Voice: H. XV. Henshaxv (1875) says of the song, “One of the most beautiful I had ever heard from any of the family,” an opinion with which the writer, who has heard nearly every species of vireo in the United States, concurs.
Grinnell and Swarth (1913) say: “The presence of the gray vireo is most easily ascertainable through the peculiar and far-reaching song.” Describing the song, which they attribute to the male only, they state: “The song of the gray vireo is loud and full-toned, in volume and quality. In these respects it reminds the hearer strongly of the Cassin Vireo, yet with the twang and less deliberate utterance of a western tanager. In measure, and in the suggestion of alternate rising and falling inflection, it recalls the least vireo.
Grinnell (1922) mentions the “broken, post-nuptially rendered song of the male: intermittent and sketchy, yet distinct enough from the songs of other vireos to be recognized at once.” Speaking of the female he said: “The only note she gave was a low harsh churr or shray, given now and then as she hopped slowly through the twiggery.”
Frank Stephens (1878) says: “They sing pretty steadily, the song consisting of a couple of syllables repeated with different inflections, something like chu: wee, chu-w~e, chu-‘w~e, generally pausing a little after three or four notes. Sometimes the order is reversed. This seems to be the song of the male, as the only female that I am positive of having heard, sung more like V. pw3illus. Sometimes when alarmed they will scold like a wren, when near to them, as they are singing, a sort of whistling sound can be heard between the notes.”
Ralph Hoffmann (1927) in an attempt to reduce the songs to syllables gives them as “chee wi, ehee wi, choo or che weet, chee; che churt wee t.”
W. E. D. Scott (1885) describes the song as “composed of single whistling notes, generally delivered rather slowly, and seemingly with hesitation, and in an abstracted way, as if the performer were thinking the while of other affairs; and yet frequently this sort of abstraction seems cast aside, and the same series of notes are given with a precision and brilliancy that calls to mind a fine performance of a Scarlet Tanager, or even of a Robin.”
Field marks: Roger T. Peterson (1941) points out that the species “has a narrow white eye-ring but differs from other Vireos having similar eye-rings by having no win gbars or one faint one.” The song and the habit of flicking the long tail nervously as the gnatcatcher does are the most readily noticed characteristics.
Elliott Coues (1866) describes the bird as follows: “Tail very long; as long as the wings; decidedly rounded; * * * The wings are short and remarkably rounded. * * * The colors of the species are almost exactly those of plum beus; * * * in form the two birds are widely diverse. It is a smaller species than plumbeus, but its greatly elongated tail make the total lengths of the two nearly the same. * * * It is unnecessary to compare vicinior with any other species, it is so very dissimilar from them all.”
Range: Southwestern United States, Lower California, and the western coast of Mexico.
Breeding range: The gray vireo breeds north to southern California (Saugus and Walker Pass, possibly); southern Nevada (Grapevine Mountains and probably Oak Spring); southwestern Utah (Beaverdam Mountains and has occurred north to Salina) northeastern Arizona (Keams Canyon); is casual or accidental at Lamar, Colorado; and extreme western Oklahoma (Kenton). East to western Oklahoma (Kenton); east-central New Mexico (Pajarito Creek near Montoya) ; and western Texas (Guadalupe Mountains near Frijole). South to western Texas (Frijole) ; southwestern New Mexico (Apache and Silver City); southern Arizona (Tombstone and Santa Catalina Mountains) ; and northern Lower California (San Rafael Valley). West to northern Lower California (San Rafael Valley) and southern California (Campo, San Jacinto Mountains, Riverside, and Saugus).
Winter range: In winter the gray vireo is as yet known only from the coast of Sonora (San Esteban and Tibur6n Islands to Guaymas) and the Cape region of Lower California. There is also a specimen, accidental or in migration, from Irde, Durango, taken on August 13, 1898.
Migration: In Sonora the extreme dates of occurrence are September Th to April.
Dates of spring arrival are: Texas: Frijole, April 30. Arizona: Santa Catalina Mountains, April 1. California: Mecca, March 26.
Dates of fall departure are: California: San Jacinto Mountains, August 27. Utah: Salina, August 22. Arizona: Grand Canyon, September 14.
Egg dates: Arizona: 7 records, May 20 to June 6.
California: 12 records, April 20 to July 4; 6 records, May 21 to 29, indicating the height of the season.