Part 34

Its flight and all its movements seem to be regulated by gnats, its days one continuous hunt for dinner. When insects are scarce it will fly hesitatingly through the air looking this way and that, its yellow rump spot always in evidence, but when it comes to an invisible gauzy-winged throng it zigzags through, snapping them up as it goes; then, perhaps, closing its wings it tumbles down to a bush, catches itself, and races pellmell after another insect that has caught its eye. In the parks it is especially fond of the palm tops frequented by the golden-crowned sparrows, and dashes around them in its mad helter-skelter fashion. The most straight-laced, conventional thing it ever does is to make flycatcher sallies from a post of observation when it has caught its insect. If it actually sits still a moment with wings hanging at its sides, its head is turning alertly, its bright eyes keen for action, and while you look it dashes away with a nervous _quip_ into midair, in hot pursuit of its prey.

It is not especially timid, being easy to approach when at its nest, and it shows its confidence in human nature by building its nest in trees in parks, over highways, in gardens, and even close to houses. Its behavior in the defense of its young shows a solicitude for their welfare. Jensen (1923) says: "If a nest with young is discovered, both parent birds try every means possible to draw the attention of the intruder away from the nest. Often I have seen them drop with folded wings from the top of a tree and flutter among the leaves as if each had a broken wing." And Grinnell, Dixon, and Linsdale (1930) write:

June 15, 1925, a female Audubon warbler was seen which showed concern whenever the observer went near a certain thicket of very small pines and willows. The bird came to within three meters of the intruder and distracted his attention by going through an elaborate display. The bird spread its tail fan-wise, showing the white spots to greatest effect, and quivered the partly spread wings, toppling over backwards at the same time, as if unable to hold to the perch. For an instant the observer thought the bird's foot was caught in the forking twigs. The inference finally made was that partly fledged young were in the low vegetation somewhere very near.

_Voice._--Samuel F. Rathbun sends me the following note on the song of Audubon's warbler: "The first note or two is given rather slowly, then its utterance is more rapid and with a somewhat rising inflection, the song closing a little hurriedly. It is quite a strong and sprightly song, but its charm lies mostly in the fact that it is one of the first, if not the very first, of the warbler songs heard in the spring. The call note given by both sexes is the same, a quick and slightly lisping one that is also used in the autumn and at times in flight."

Dr. Walter P. Taylor (MS.) says of a song heard at Fort Valley, Ariz., on June 12, 1925: "The song seems much less full and seems lacking in quality, as compared with that of the Audubon in Washington State. It was so lacking in strength and quality that I took it for a Grace warbler." He wrote it as _wheetlea, wheetlea_, repeated 7 or 8 times, or _wheetoo_, 7 times repeated, or again _wheetleoo wheet_, the final syllable a little different from the others.

Mrs. Bailey (1902) says: "His song is of a strong warbler type, opening toward the end, _chwee, chwee-chwee-ah, chwee_, between the song of the yellow warbler and that of the junco." At Lake Burford, N. Mex., in May and June, according to Dr. Wetmore (1920), "males were found singing from the tops of the tallest pines and were slow and leisurely in their movements in great contrast to their habit at other seasons. Frequently while singing they remained on one perch for some time so that often it was difficult to find them. The song resembled the syllables _tsil tsil tsil tsi tsi tsi tsi_. In a way it was similar to that of the Myrtle Warbler but was louder and more decided in its character."

Dr. Merrill (1888) says: "On two or three occasions I have heard a very sweet and peculiar song by the female, and only after shooting them in the act of singing could I convince myself of their identity."

_Field marks._--The male in his gay spring plumage is not likely to be confused with any other warbler except the myrtle warbler, from which it differs in having a brilliant yellow throat instead of a white one; in other words, _auduboni_ has five patches of yellow against four for _coronata_. In immature and fall plumages the two species are much alike, but _auduboni_ has four or five large white patches on each side of the tail, while _coronata_ has only two or three, in the different plumages; these white markings are diagnostic in any plumage. The yellow rump is always conspicuous at any season, even when the other yellow markings are more obscured.

_Fall._--The fall migration is a reversal of the spring migration, from the north southward and from the mountains down to the valleys and lowlands. Rathbun tells me that the southward migrants pass through Washington during October and November, but that a few remain there and even farther north, in winter. In California, Audubon's warblers that have bred in the mountains begin to drift downward to lower levels in August, the young birds coming first, so that by September they are well spread out over the lowlands almost down to sea-level. Soon after the first of October, the first of the migrants cross the border into Mexico on their way to winter quarters. Dr. Taylor tells me that in New Mexico during October these warblers are abundant in the aspens, being "by far the most numerous species of bird."

_Winter._--Audubon's warbler is a hardy bird. At least some individuals remain in winter almost up to the northern limit of its breeding range; and while it retires entirely from its summer haunts in the mountains, most of its breeding range elsewhere is not wholly deserted. It probably remains as far north as it can make a living; its adaptability in finding a food supply helps in this and makes it one of the most successful of western birds as well as one of the most abundant in all parts of its range. A few remain, perhaps regularly, in coastal British Columbia, for Theed Pearse has given me five December dates and four February dates, spread out over a period of 10 years, on which he has recorded one or more Audubon's warblers on Vancouver Island; on one of these dates, February 10, 1943, the temperature dropped to -6° F.

Rathbun tells me it is "of frequent, if not regular, occurrence during the winter" in Washington. And in Oregon Gabrielson and Jewett (1940) record it as a "permanent resident that has been noted in every county during summer and throughout western Oregon in winter. * * * Its little song is heard on every side during May and June, and its peculiarly distinct call or alarm note is a familiar sound throughout the balance of the year. This is true not only of the wooded slopes and bottoms but equally so of the weedy fence rows of the Willamette Valley, where during the short days of fall and winter these warblers may be found associating with the Golden-crowned Sparrows and Willow Goldfinches or sitting on the telephone wires with the Western Bluebirds." Swarth (1926) writes:

In much of the West, especially in the Southwest, the Audubon's warbler is one of the dominant species during the winter months. In southern California it vies with the Intermediate Sparrow and House Finch in point of numbers. Wherever there are birds at all, this bird is sure to be there. From the seacoast to the mountains, in city parks and gardens, in orchards and in chaparral, the Audubon's warbler is equally at home. On any country walk scores are sure to be seen, starting up from the ground or out of the trees with wavering and erratic flight, showing in departure a flash of white-marked tail-feathers and a gleaming yellow rump spot, and uttering the incessant _chip_ that, better than any marking, serves to identify the fleeting bird.

In colder sections there are some fatalities; in the Fresno district, according to Tyler (1913), "a period of two or three unusually cold nights frequently results disastrously for these little warblers, and my observations show that there is a greater mortality among this species than in all other birds combined. After a hard freeze it is not an uncommon occurrence to see certain individuals that appear so benumbed as to be almost unable to fly, and not a few dead birds have been been found under trees along the streets."

From much farther south, in Central America, Dr. Alexander F. Skutch (MS.) writes:

"Audubon's warbler is a moderately abundant winter resident in the higher mountains of Guatemala, yet like the closely related myrtle warbler, appears to be less regular in its time of arrival and departure and less uniformly distributed, than the majority of the more common winter visitants. These attractive warblers were abundant on the Sierra de Tecpán from January until April, 1933; but strangely enough they did not return in August or September with all the other warblers that winter there; and none had appeared by the end of the year, although I kept close watch for them. Yet in the middle of the following September, I found them numerous among the pine and alder trees on the Sierra Cuchumatanes, nearly 11,000 feet above sea-level. The males were then resplendent in their full nuptial dress of yellow, black, white and gray, and sang enchantingly. I believe it not impossible that they breed in this remote, little-known region--for here also I found a breeding representative of the savannah sparrow, hitherto known only as a migrant in the country--and it is to be hoped that some day an ornithologist will study the bird-life of this lofty plateau during the breeding season, from April to August.

"During the winter months, the Audubon warblers are truly social, and are nearly always met in flocks, sometimes containing 25 or more individuals. They are versatile in their modes of finding food. Sometimes, from the tops of the tall cypress trees near the summit of the Sierra de Tecpán, they would launch themselves on long and skillfully executed sallies to snatch up insects on the wing. As they twisted about in the air, they would spread their tails to reveal the prettily contrasting areas of black and white. At other times they foraged on the ground, like the myrtle warblers; and this habit brought them into contact with the bluebirds (_Sialia sialis guatemalae_), which are likewise arboreal birds that frequently descend to hunt on the ground. At altitudes of 8,000 to 9,000 feet I almost always found the Audubon warblers and the bluebirds together in the bare, close-cropped pastures where there were scattered, low, oak trees; and this association was so constant that it could not have been accidental. Both kinds of birds were exceedingly wary as they hunted over the ground, and would fly up into the trees if they espied a man approaching them, even from a long way off. The Audubon warblers, probably because they more frequently enter open, exposed places, where they are conspicuous and far from shelter and must exercise great caution not to be surprised, were by far the shiest and most difficult to approach of all the warblers of the Sierra, whether resident or migratory. This was true whether they happened to be in the trees or on the ground.

"In the evening, foraging over the ground as they went, the Audubon warblers and bluebirds would go together to bathe in one of the rivulets that flowed through the pastures. After splashing vigorously in the shallow water they would fly up together into the raijón bushes, shake the drops from their feathers, sometimes wipe their wet faces against the branches, and put their plumage in order again. The last Audubon warbler that I saw in the spring was a lone female, who foraged in company with a pair of the resident bluebirds in the open pasture. She must have appreciated the companionship of the bluebirds more than ever, after all of her own kind had departed for more northerly regions.

"Guatemalan dates are: Sierra de Tecpán, January 16 to April 23, 1933; Sierra Cuchumatanes, September 13, 1934; Chichicastenango (Griscom), November 16."

DISTRIBUTION

_Range._--Western North America from central British Columbia to Guatemala.

_Breeding range._--Audubon's warbler breeds =north= to central British Columbia (Hazelton, Fort St. James, and Nukko Lake) and central western Alberta (Smoky River). =East= to southwestern Alberta (Smoky River, Jasper Park, Banff National Park, and Crowsnest Lake); casually to southwestern Saskatchewan (Cypress Hills); western Montana (Fortine, Teton County, Bozeman, and Fort Custer); western South Dakota (Harding County and the Black Hills); northwestern Nebraska (Warbonnet Canyon, Sioux County); central Colorado (Estes Park, Gold Hill, Colorado Springs, Wet Mountains, and Fort Garland); central New Mexico (Taos, Ruidoso, and Cloudcroft); western Texas (Guadalupe Mountains); and western Chihuahua (Pinos Altos); in migration much farther east. =South= to central western Chihuahua (Pinos Altos); southeastern to north-central Arizona (Huachuca Mountains, Santa Catalina Mountains, Flagstaff, and Grand Canyon); southwestern Utah (Zion National Park); southern Nevada (Charleston Mountains); central southern California (San Bernardino Mountains and the Santa Rosa Mountains); and northern Baja California (Sierra San Pedro Mártir). =West= to northern Baja California (Sierra San Pedro Mártir); southwestern California (San Jacinto Mountains and Mount Wilson); central eastern California (Yosemite Valley and Big Trees); western California (Diablo, Mount Tamalpais, Fort Ross, and Trinity Mountains); western Oregon (Coos Bay, Eugene, Corvallis, and Netarts); western Washington (Cape Disappointment, Shelton, and the San Juan Islands); and western British Columbia (Cowichan Lake and Port Hardy, Vancouver Island; and Hazelton).

_Winter range._--The Audubon warbler is found in winter =north= to southwestern British Columbia (Comox and Chilliwack). =East= to southwestern British Columbia (Chilliwack); central Washington (Yakima); occasionally eastern Washington (Cheney); northeastern Oregon, casually (Pendleton and Legrande); central California (Marysville and Fresno); casually to southwestern Utah (St. George and Zion National Park); central Arizona (Fort Mojave, Fort Verde, Salt River National Wildlife Refuge, and Tombstone); southern Texas (El Paso, rarely Knickerbocker, and Brownsville); Tamaulipas (Matamoros and Victoria); western Veracruz (Orizaba); and central Guatemala (San Jerónimo). =South= to Guatemala (San Jerónimo, Tecpán, and San Lucas); casual or accidental south to central Costa Rica (Juan Viñas). =West= to western Guatemala (San Lucas and Totonicapán); Oaxaca (Parada); Guerrero (Chilpancingo and Coyuca); western Jalisco (Tonila); Nayarit (Tepic); southern Sinaloa (Mazatlán); western Baja California (Santa Margarita and Natividad Islands); and the west coast of the United States to southwestern British Columbia (Comox).

The preceding range is for the species as a whole of which two subspecies or geographic races are recognized. The Pacific Audubon's warbler (_D. a. auduboni_) breeds south to southern California, central Arizona, and New Mexico; the black-fronted Audubon's warbler (_D. a. nigrifrons_) breeds from the Huachuca Mountains, Ariz., through the mountains to southwestern Chihuahua.

_Migration._--Late dates of spring departure from the winter range are: Guatemala--Tecpán, April 23. Sonora--Moctezuma, May 23. Texas--Marathon, May 18. Kansas--Fort Wallace, May 27. Arizona--Prescott, May 19. California--Fresno, May 3.

Early dates of spring arrival are: Kansas--Garden City, April 22. Nebraska--Hastings, April 14. New Mexico--Apache, March 7. Colorado--Colorado Springs, April 12. Wyoming--Laramie, April 21. Montana--Fortine, April 14. Alberta--Banff, April 23. Utah--St. George, March 8. Nevada--Carson City, April 10. Idaho--Sandpoint, April 16. California--Grass Valley, April 10. Oregon--Prospect, March 6. Washington--Shelton, March 4. British Columbia--Summerland, March 30.

Late dates of fall departure are: British Columbia--Okanagan Landing, October 24. Washington--Pullman, November 13. Oregon--Prospect, November 18. Idaho--Bayview, October 26. Utah--St. George, December 7. Alberta--Edmonton, September 11. Montana--Fortine, October 24. Wyoming--Laramie, November 9. Colorado--Fort Morgan, October 30. New Mexico--Silver City, November 10.

Early dates of fall arrival are: California--San Diego, September 2. Texas--Fort Davis, September 9. Sonora--Las Cuevas, September 3. Guatemala--Chichicastenango, November 16.

_Banding._--An Audubon's warbler that was banded at Santa Cruz, Calif., on February 17, 1931, was found dead November 5, 1931, at Glenwood, Calif. Another, banded at Altadena, Calif., on December 1, 1935, was retrapped at the same station on February 13, 1940, being then nearly 5 years old, at the least.

_Casual records._--A specimen of Audubon's warbler was collected at Cambridge, Mass., on November 15, 1876. Another was collected at West Chester, Pa., November 8, 1889. In Ohio one was closely watched at Cleveland April 30 and May 3, 1931; and a second one at Richmond on October 5, 1941. On April 28, 1928, one was closely watched at Minneapolis, Minn.

_Egg dates._--California: 53 records, May 11 to July 30; 28 records, June 13 to 25, indicating the height of the season.

Colorado: 10 records, June 18 to July 6; 5 records, June 19 to 29.

Washington: 11 records, April 19 to June 29; 5 records, May 14 to June 13.

DENDROICA AUDUBONI NIGRIFRONS (Brewster)

BLACK-FRONTED AUDUBON'S WARBLER

HABITS

The black-fronted Audubon's warbler was originally described by William Brewster (1889) as a distinct species, based on a series of five specimens collected by M. A. Frazar in the Sierra Madre Mountains of Chihuahua, Mexico, in June and July, 1888. He gave as its characters: "Male similar to _D. auduboni_ but with the forehead and sides of the crown and head nearly uniform black, the interscapulars so closely spotted that the black of their centres exceeds in extent the bluish ashy on their edges and tips, the black of the breast patch wholly unmixed with lighter color. Female with the general coloring, especially on the head, darker than in female _auduboni_; the dark markings of the breast and back coarser and more numerous; the entire pileum, including the yellow crown patch, spotted finely but thickly with slaty black." He admits that it is closely related to _D. auduboni_, "so closely in fact that the two may prove to intergrade," but he found no indications of such intergradation. Later, however, Leverett M. Loomis (1901) called attention to the fact that several birds, collected in the Huachuca and Chiricahua Mountains, in Arizona, showed signs of intergradation with breeding birds from central California. These were taken by W. W. Price, establishing this bird as an addition to our fauna, and resulting in its reduction to subspecific rank. It is known to breed in the Huachuca Mountains and in the high Sierras of northwestern Mexico, ranging south to Guatemala. Swarth (1904) says of the status of the black-fronted warbler in Arizona:

This, the only form of _auduboni_ that breeds in the Huachucas, occurs during the summer months, though in rather limited numbers, in the higher pine regions from 8500 feet upwards. On one occasion, April 5, 1903, I secured a male _nigrifrons_ from a flock of _auduboni_ feeding in some live-oaks near the mouth of one of the canyons at an altitude of about 4500 feet, but this is the only time that I have seen it below the altitude given above; and it is also exceptional in the early date of its arrival. No more were seen until the second week in May, which seems nearer the usual time of arrival, for in 1902, the first was seen on May 9th. * * * Several specimens were taken intermediate in their characteristics between _auduboni_ and _nigrifrons_; some, of the size of the latter, though in color but little darker than _auduboni_, while some show every gradation of color between the two extremes.

The black-fronted warbler averages somewhat larger than the Audubon's.

_Nesting._--Before this warbler was known to be the breeding form in Arizona, O. W. Howard (1899) reported on two nests found in the Huachuca Mountains in 1898, and said that he had found "several nests" of Audubon's warblers in 1897 and 1898, all in these mountains. These were all, doubtless, nests of the black-fronted warbler. One of these was in a red fir tree about 15 feet up, and the other "was placed in the lower branches of a sugar-pine about fifty feet from the ground, and twelve feet out from the trunk of the tree. * * * The nests are very loosely constructed, being composed almost entirely of loose straws with a few feathers and hair for a lining." One of Howard's nests of this warbler, with four eggs, is in the Thayer collection in Cambridge. It was found in the same mountains, at an elevation of about 9,000 feet, saddled on the limb of a red spruce tree 35 feet above ground and well concealed in the foliage. It is rather a bulky nest made of shredded weed stems, fine strips of inner bark, fine rootlets and various other plant fibers, mixed with feathers of the Arizona jay, three long wing feathers of small birds and two small owl feathers; it is lined with fine fibers, horse and cattle hair, and jay feathers. Externally it measures about 3-1/2 inches in diameter and 2-1/2 in height; the inside diameter is about 2 inches and the cup is about 1-3/4 inches deep.

James Rooney has sent me the data for a set of four eggs of the black-fronted warbler, taken by Clyde L. Field in the Santa Catalina Mountains in Arizona, June 2, 1938. The nest, placed 15 feet above ground at the end of a pine limb, was made of twigs and was lined with deer hair and a few feathers. A nest with four eggs, in the collection of Charles E. Doe, in Florida, was taken by the same collector in the same mountains on June 8, 1937; it was in a crotch of an aspen, 30 feet up.

_Eggs._--The measurements of 16 eggs average 18.5 by 13.6 millimeters; the eggs showing the four extremes measure =19.8= by 14.0, 19.5 by =14.4=, =17.3= by 13.9, and 17.6 by =12.4= millimeters (Harris).

DENDROICA NIGRESCENS (Townsend)

BLACK-THROATED GRAY WARBLER

PLATE 35

HABITS

The black-throated gray warbler is neatly dressed in gray-black and white, with only a tiny spot of bright yellow in front of the eye. Its breeding range extends from southern British Columbia, Nevada, northern Utah, and northwestern Colorado southward to northern Lower California, southern Arizona, and southern New Mexico. It spends the winter in Mexico.

As a summer resident it is common and sometimes abundant in western Washington, even at lower elevations where, Samuel F. Rathbun tells me, it "prefers a locality somewhat open, with a second growth of young conifers; this may occur in the rather heavy forest, if such condition exists there, or along the edge of the timber; the species is partial to this character of growth."

In southern Oregon, according to C. W. Bowles (1902), it seems to combine the habitat requirements of the eastern black-throated green and the prairie warbler. Like the former, it seeks tall trees, preferably conifers, well scattered and interspersed with bushes, since it nests in both. Like the prairie warbler, it chooses high dry places with dry ground underneath for its nest.