sexes, the female being somewhat duller than the male and often with
little or no yellow on the throat. In both sexes the plumage is browner
throughout, the yellow areas are paler and less pronounced, the black
streaks are less prominent, and the white areas in the tail are more
restricted than in fall adults. Swarth continues: "All winter long these
drab-colored birds pervade the lowlands, conspicuous only through force
of numbers. Then, the latter part of March, comes the prenuptial molt
that brings such marked changes to the male. This molt is extensive, far
more so than with most of our birds in the spring, since it includes all
of the plumage except flight-feathers and tail-feathers. At the close
of the spring molt, about the middle of April as a rule, the male
emerges, gorgeous in black breast and yellow trimmings, and with a showy
white patch on either wing. The female, with similarly extensive molt,
has changed but little in appearance." He probably intended this as a
description of the adult prenuptial molt, but that of the young bird is
practically the same. However, the young bird in first nuptial plumage
can always be recognized by the faded and worn primaries and tail
feathers; otherwise, young and old are essentially alike. Adults have a
complete postnuptial molt in August and a partial prenuptial molt, as
outlined, in early spring. Mr. Swarth (1926) says: "In winter plumage,
old and young, male and female, are all very similar, but there are
minor differences by which the old male, at least, may be told from the
others. The dark streaks on the sides of the breast are a little more
pronounced, the yellow markings a little brighter, and the body color a
little clearer gray, as compared with the browner young birds."
Hybrids, or intergrades, occur occasionally between the different races
of _auduboni_ and _coronata_ where their ranges approach or overlap.
_Food._--Professor Beal (1907) examined the stomachs of 383 Audubon's
warblers taken in California from July to May, inclusive. The food
consisted of 85 percent of animal matter (insects and spiders) and a
little more than 15 percent of vegetable matter. The largest item was
Hymenoptera, 26 percent, consisting mostly of ants, with some wasps, and
a few parasitic species. Diptera accounted for 16 percent, including
house flies, crane-flies, and gnats, many of which must have been caught
on the wing, as this warbler is a good flycatcher. Bugs, Hemiptera,
amounted to nearly 20 percent of the food, including the black olive
scale, other scales, plant-lice, stink bugs, leaf-hoppers and
tree-hoppers. "Plant lice (Aphididae) were contained in 39 stomachs, and
from the number eaten appear to be favorite food. Several stomachs were
entirely filled with them, and the stomachs in which they were found
contained an average of 71 percent in each." Caterpillars amounted to
nearly 14 percent and beetles more than 6 percent of the food; most of
the beetles were injurious species. Other insects and spiders made up
about 2 percent.
The vegetable food consisted of fruits, mostly wild and of no value,
less than 5 percent, and seeds, over 9 percent, mostly weed seeds and
seeds of the poison oak. These warblers have been known to puncture
grapes and they probably eat some late fruit, but they do very little
damage to cultivated fruits and berries. C. S. Sharp (1903) observed a
flock of 200 birds, mostly Audubon's warblers, greedily eating the
raisins in the tray shed of his packing house; they had to be constantly
driven away. Mrs. Amelia S. Allen says in her notes that they collect in
great flocks in the live oaks to feed on the oak worms in the spring,
and that they eat myrica berries in the fall. John G. Tyler (1913) says:
"Audubon warblers share with Say Phoebes the habit of catching flies
from a window, sometimes becoming so engrossed in this occupation as to
cling for several seconds to the screen where a south-facing window
offers a bountiful supply of this kind of food."
_Behavior._--Audubon's warbler is a lively and active bird that seems to
be always in a hurry, constantly moving in pursuit of its prey. Mrs.
Bailey (1902) writes:
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: