A member of the hard to identify group of Empidonax flycatchers, the Pacific-slope Flycatcher was split from the Cordilleran Flycatcher, the two of which were once known as the Western Flycatcher. Differences in appearance, voice, and genetics of Pacific-slope and Cordilleran Flycatchers led to this split, although questions remain about exactly how populations in some areas should be classified.
Most Pacific-slope Flycatcher populations are migratory, although little is known about their migration habits. Steller’s Jays are known nest predators in some areas. An alarm call is given if this or other predators are spotted. The oldest known Pacific-slope Flycatcher in the wild lived over six years.
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Description of the Pacific-slope Flycatcher
The Pacific-slope Flycatcher is olive above and faint yellowish below with a whitish eye ring that is wider in the rear, and two wing bars. Its lower mandible is orange.
Seasonal change in appearance
Juveniles resemble adults but have tawny wing bars.
Forages by flying out from a perch to capture flying insects.
Breeds in the far western U.S. and Canada.
Pacific-slope Flycatchers sometimes chase Hammond’s Flycatchers away from their territories .
Pacific-slope Flycatchers have an alarm call they give when a predator is near.
A three-syllable song and several shorter calls are given.
- Cordilleran Flycatchers and other Empidonax flycatchers appear very similar. See vocalizations.
The nest is a cup of plant materials placed in a tree or stream bank.
Color: White with darker markings.
Incubation and fledging:
– Young hatch at 14-15 days.
– Young fledge (leave the nest) in 14-18 days after hatching but remain with the adults for some time.
Bent Life History of the Pacific-slope Flycatcher
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 Pacific-slope Flycatcher – the common name and sub-species reflect the nomenclature in use at the time the description was written.
EMPIDONAX DIFFICILIS DIFFICILIS BairdHABITS
This flycatcher was formerly called the western yellow-bellied flycatcher and was at one time treated as a subspecies of our eastern fiaviven.trk; but it is now recognized as a distinct species, as it belongs to a group of Empidonaces having a different wing formula; it also has a longer tail than flaviver&tri8 and differs from it in some of its habits.
The western flycatcher is widely distributed in western North America, chiefly from the Rocky Mountains westward, from Alaska to southern California and Texas, with other races m Lower California and Mexico.
Unlike the yellow-bellied flycatcher, which it superficially resembles, it is not especially partial to the coniferous forests in the breeding season, but is much more generally distributed and nests in a much greater variety of situations. S. F. Rathbun says in his notes on this species: “This small flycatcher is a common summer resident of western Washington. I have found it from the Cascade Mountains to the Pacific Ocean, and its distribution appears to be general, although it seems to occur much oftener in the lower country. It is a bird to be looked for in woods mostly deciduous, where maples, alders, and dogwoods grow, for it shows little fancy for the evergreen growth; and in the former it is usually found in the vicinity of low ground. A good place to find this flycatcher is in some quiet glen, especially if such has a trickling little stream, and here its note will be frequently heard. But wherever it occurs, the place is apt to be a quiet one, for it is a bird that seems fond of the stillness of the woods.
“Usually it arrives in this section near the close of April. It begins to nest by the first of June and continues to do so throughout the month, but on occasions its nest will be found in July.”
Nesting: Mr. IRathbun writes (MS.) on this subject: “This flycatcher does not seem at all particular in its choice of a nesting place, but from our experience the locality selected is invariably within the woods. I have found its nest, at various heights, from 3 to 30 feet, although the latter was exceptional, and in all kinds of spots. At times the nest will be placed among the roots of an upturned tree, again on the top of a low stump, or in the crotch of a very small tree; and once I found its nest in the crown of a devil’s-club (EcAinopan~a~ horridum), a showy shrub bearing countless spines and little prickles irritating to the skin, a most unusual place for a bird’s nest. And the localities favored are usually in a somewhat retired part of the forest, near low ground. Oftener than not green and dry mosses represent most of the nest, and invariably it is lined with fine strips of shredded bark. On one occasion I found a nest of this bird that was so beautiful I will describe it. It was placed at a height of 15 feet in the main crotch of a little alder tree growing near the edge of a bit of swampy ground not far within the border of the woods. All the material used in this nest, except its lining, was ground moss of a rich dark-green color, enough being used to fill the small crotch to a height of about 5 inches. The inside of the nest was a round depression in the quite level top surface of the moss, it having a diameter of 13,4 inches with a depth of 11,4. This depression was lined entirely with fine shreds of inner bark of the cedar, the texture of which was very soft. It was neatly, very smoothly woven, showing a high degree of skill; and, because of its reddish color, it made a beautiful contrast to the dark-green moss. The inside rim of this nest was a perfect circle; never in any bird’s nest have I seen one so flawless; and it seemed to me that the maker of this particular nest had at least some sense of artistry.”
Major Bendire (1895) mentions a number of quite different nesting sites. C. A. Allen, of Nicasio, Chlif., wrote to him:
I have found Its nests in all sorts of situations; sometimes in a small true, placed in the upright forks of the main stem; again on the side of the stem, where a small stub of a limb or some sprouts grew out; or in a slight cavity in a tree trunk; against an old stump or root which had been washed down during a flood in the middle of a stream; among curled-up roots near the water, etc. I have found a number of nests, when fishing for trout, by flushing the bird from under a hank; and on stooping down and looking I found the nest nicely concealed by the deep-green moss, such as covered the surrounding stones. They always use this particular kind of moss, no matter where the nest is placed. Occasionally they nest In deserted woodcutters’ huts, in outbuildings near cover, and a friend of mine has some large water tanks in the woods back of his house, where for nineteen consecutive years these birds have built under the covered roofs of these tanks. I know of no place in this locality where they do not breed, excepting in very open country. * * * In Belt Canyon, Montana, on July 6, 1889, Mr. R. S. Williams found the Western Flycatcher nesting in a narrow fissure of limestone, about 7 feet above the base of the wall. A nest observed by Mr. A. W. Anthony, near Howardsyule, San Juan County, Colorado, on June 25, was placed on a ledge of rock, about 10 feet above a wagon road, and looked like a large ball of green moss, with a neat little cup in the center, lined with cow and horse hair. * * * Mr. A. M. Ingersoll reports finding a nest of this species at the bottom of a hole 5 Inches deep, made by a Red-shafted Flicker in a live oak; nests have also been taken in piles of driftwood, on beams under bridges, etc. * * * The nest Is composed of weed stems, dry grasses, plant fibers and down, strips of the inner bark of the redwood, fine rootlets, dead leaves, and bits of moss. It Is usually lined with finer materials of the same kind, and occasionally with horse and cattle hair or a few feathers. The outside of the nest is usually coated with green moss when obtainable, but some nests before me show no trace of this in their composition. They are generally placed not far from water, but there are exceptions to this. A well-preserved nest now before me, * * * measures 4 inches in outer diameter by 2 Inches in height. The inner cup measures 2V4 inches by 194 inches deep.
That this flycatcher does not always nest in the solitude of the forests is shown by the nests reported by Dr. Grinnell (1914a) on the Berkeley Campus: “In one case a brood was reared in a nest ensconced in a niche 18 feet above the ground in the side of an oak trunk near the Faculty Club. In another instance, the nest was built in a fern basket on a porch at 2243 College Avenue. This site was but five feet from a frequently used door, and it was only two feet from the porch-light which shone into the nest on frequent occasions in the evening without appearing to disturb the birds. On May 17 (1908) this nest held four eggs, and two young were successfully reared. In 1909, the same site was chosen, but the nest was subsequently deserted.”
Nesting sites on beams in unoccupied buildings are often used year after year, until a whole row of old nests may sometimes be seen. Nests built in trees may be placed on any suitable support, in a natural crevice, or behind loose slabs of bark, such as occur on redwoods, alders, or eucalyptus trees. These birds are not only very much attached to favorite nesting sites, especially in buildings, but are sometimes very persistent in their attempts to raise a brood. Joseph Mailliard (1881) tells of a pair that nested every year in the shed covering his tanks. One season he took five nests with eggs from this same pair of birds in the same shed. The first nest was taken on May 15 and the last on July 6. Thus five nests were built and 21 eggs were laid by this pair of birds in a little over two months.
Denis Gale says in his notes that he has known one pair of these birds to use the same nest for three years in succession and another pair for four, repairing the old nest or partially rebuilding it.
Eggs: Three or four eggs are ordinarily laid by the western flycatcher, usually four and very rarely five. The eggs vary from ovate to short-ovate or even rounded-ovate. They are practically lusterless, with a dull white or creamy white ground color. The markings consist of spots or small blotches, usually concentrated about the larger end, but on some eggs there are minute dots or small spots scattered more or less evenly over the whole surface. These markings are in shades of bright reddish brown, “cinnamonrufous,” or the lighter shades of “buff-pink”; occasionally there are a few faint spots of lavender. Bendire (1895) says that “the spots are, as a rule, coarser and heavier” than on the eggs of the yellowbellied flycatcher. The measurements of 50 eggs average 16.8 by 13.1 millimeters; the eggs showing the four extremes measure 18.8 by 13.7, 18.0 by 14.2, and 15.2 by 12.5 millimeters.
Young: The period of incubation is said to be 12 days. Whether both sexes incubate does not seem to be known, but both parents assist in the feeding of the young and probably in brooding them also. Professor Beal (1910) says that the food of the young shows no marked difference from that of the adults. “The young in one nest were fed 24 times in an hour. Owing to the nest’s location the number of nestlings was not ascertained. If there were four, as is probable, and the feeding was continued fourteen hours, each was fed 84 times during the day.”
Plumages: I have seen no very young specimens of the western flycatcher. The sexes are alike in all plumages, and in juvenal plumage the young birds are much like the adults, but much browner above, and paler yellow or huffy below; the wing bands are “cinnamon-buff” or “ochraceous” The molts. of this species apparently correspond to those of the yellow-bellied flycatcher, to which the reader is referred. The postjuvenal molt occurs long after the young birds have left for the south and the prenuptial molt is accomplished before the birds return in the spring, consequently molting specimens are scarce in collections. What few specimens are available seem to indicate that young birds molt the body plumage late in the fall and have a complete prenuptial molt in ‘late winter or spring. Adults seem to follow a similar sequence, with perhaps a renewal of the flight feathers during the winter. More winter ~pe~imens are needed to trace these molts.
Food: Professor Beal (1910) examined 141 stomachs of the western flycatcher, and his “analysis gives 99.28 percent of animal food to 0.72 percent of vegetable.” Of the animal food this bird appears to eat more ladybird beetles than does any other flycatcher, more than 7 percent of the food in August, but an average of only 21/s percent for the season. He says:
Other beetles amount to nearly 6 percent, nearly all harmful, the exception being a few ground beetles (Carabidae).
Hymenoptera form the largest constituent of the food of this as of most other flycatchers. They amount to over 38 percent. * * * No honeybees were identified. ï * Hemiptera (bugs) amount to nearly 9 percent of the food. * * Diptera amount to a little more than 31 percent of the whole food. ï * * Lepidoptera, In the shape of moths and caterpillars, amount to about 7 percent for the year, and were found in every month except March. They appeared in 86 stomachs, of which only 7 contained the adult insects: moths: and 29 the larvae or caterpillars. * A few unidentified insects and some spiders make up the remainder of the animal food: about 6 percent.
Vegetable matter was found in 16 stomachs, though some of it could not properly be called food. One stomach contained seeds of Rubus fruit (blackberries or raspberries) ; 7, seeds of elderberries; 1, the skIn of an unidentified fruit and a seed of tarweed (Media); while 6 held rubbish. The Rubus fruit mIght have been cultivated, but probably was not.
Theed Pearse writes to me that he saw one of these flycatchers capture a good-sized fly on a branch, hold it on the branch with its feet, and tear it with its beak. Most of its food is probably captured on the wing.
Behavior: There seems to be nothing peculiar in the behavior of the western flycatcher, as compared with the other small flycatchers of the Empidona~ group. Both parents are devoted to the defense of their home and family, and. the male stands guard nearby while the female is incubating and drives away any other birds that venture too near the nest. Mr. Pearse tells me that the flight is hesitating, like that of the kingbird. I am not acquainted with the bird in life.
Voice: Mr. Pearse (MS.) mentions an alarm note similar to the tsip alarm note of warbiers, and another alarm note that resembles the call of Harris’s woodpecker, but he writes the usual note as pisint.
Ralph Hoffmann (1927) writes: “From under live oaks in a canyon, from deciduous trees near a stream or even from shady plantations about dwellings from April to July a single sharp note, pee-i et , like the expiration of wheezy breath, catches the ear of an attentive listener. * * * Besides the pee-ist note, almost but not quite two syllables, the Western Flycatcher utters a low whit. In the breeding season the male repeats, often for long periods from the same perch, three syllables which constitute his attempt at song, ps-s~et ptsicle, and after a slight pause sst.’~ Grinnell and Storer (1924) write:
On the morning of June 3, 1915, a Western Flycatcher was watched as It sang and foraged among the big-trunked incense cedars and huge mossy boulders on the north side of the Yosemite Valley, at the foot of Rocky Point. The greenish yellow of the bird’s upper plumage and its yellowish under surface were the only sight characters available, but the call note and song were both distinctive. The former was a single high-pitched, even piercing, swee ip or twee it; less often a fainter peet was uttered. The song goes seA rip, sip, sed rip, or sometimes se.~ rip, sert, sip, see rip, and is repeated over and over again, often so continuously that the pauses between songs seem no greater than the intervals between the constituent notes. The syllables were given in varying order, and often the single combination, see rip, was uttered over and over again. While singing, this bird was perched on various twigs and branches 10 to 20 feet above the ground. The song is to be heard most often in May and early June, but as late as July 30 a bird was heard in full summer song.
Bendire (1895) quotes C. A. Allen as saying: “Its song consists of a soft, low note. It shows much distress when its nest is taken, uttering then a low, wailing note, like ‘pee-eu, pee-eu’ and frequently flutters about the person taking it and snapping its mandibles together.”
Field marks: The small flycatchers of the Empidona~x group are very difficult to distinguish in the field by color characters alone. The western flycatcher is more olivaceous above and more extensively yellowish below, with a much brighter shade of yellow, especially on the belly, than any of the small western species; but there are three other western species that are more or less yellowish on the under parts, trailli, kammondi, and wrighti, all of which closely resemble difficilis in other respects. Fortunately the habitats of the four species are somewhat different. Ralph Hoffmann (1927) says on this point: “The Traill Flycatcher is very similar in appearance to the Westem, but though often found in the same general region, is restricted to willow thickets and to bushy places in wet mountain meadows. * * * The Western Flycatcher, though it also affects the neighborhood of streams, demands for its hunting a certain amount of open space in the shade of tall trees of mixed growth; neither the Western nor the Wright would be found regularly in the dense willow thickets which the Traill prefers.” Wright’s flycatcher is more likely to be found at higher elevations on the mountain siopes, and Hammond’s frequents the tall coniferous forests. But the best character by which these species may be distinguished is the call note or song, which the keen ear of a good observer can learn to recognize, as the notes of the four are quite different; when the birds are not singing, identification is often almost hopeless.
Fall: Mr. Rathbun says in his notes from Seattle: “After the end of the breeding season, when its young are on the wing, this flycatcher appears to move about the country, for it is apt to be heard or seen almost anywhere, even at times in the cities and towns. This movement is but preliminary to its fall migration, which takes place in September, and after late in this month the species is no longer seen.”
Range: Southeastern Alaska, British Columbia, and Western United States and Mexico.
Breeding range: The western flycatcher breeds north to southeastern Alaska (Sitka and Juneau); east-central British Columbia (Salmon River Forks); Montana (Belt River Canyon); northern Wyoming (Yellowstone Park and Sheridan); and probably western South Dakota (Box Elder). East to probably western South Dakota (Box Elder); southeastern Wyoming (Wheatland); Colorado (Estes Park, Goldhill, and Hancock); New Mexico (Twining, Sacramento Mountains, and Guadalupe Mountains); and western Texas (Chisos Mountains). South to southwestern Texas (Chisos Mountains); Chihuahua (Pinos Altos); Nayarit (Isabela Island); and northern Baja California (San Fernando). The western limit of the breeding range extends northward from northern Baja California (San Fernando and Vallecitos), along the coasts and islands of California, Oregon, Washington, and British Columbia, to southeastern Alaska (Forrester Island, Ketchikan, and Sitka).
Winter range: The winter range of the western flycatcher is in western Mexico from southern Baja California (La Paz and San Jose del Rancho) and southern Sonora (Chinobampo, Tesia, and Alamos) south to southern Guerrero (Coyuca and Chilpancingo) and Oaxaca (Pluma).
The range as outlined includes the two North A,merican races of this species. The typical western flycatcher (Empidonax diflicili.s difficilis) is the form found in the United States, Canada, and Alaska, while the San Lucas flycatcher (F. d. cineritius) is confined to Baja California. An additional nonmigratory race is found in central and southern Mexico.
Spring migration: Early dates of spring arrival are: New Mexico: Apache, May 12. Colorado: Littleton, May 11. Wyoming: Wheatland, May 15. Montana: Fortine, May 14. Arizona: Tucson, March 24. California: Berkeley, March 12. Oregon, Weston, March 20. Washington: Tacoma, March 24. British Columbia: Courtenay, March 31. Alaska: Ketchikan, May 6.
Fall migration: L ate dates of fall departure are: Alaska: St. Lazaria Bird Reservation, September 30 (unusually late). British Columbia: Courtenay, September 9. Washington: Seattle, September 17. Oregon: Coos Bay, September 20. California: Pasadena, October 10. Wyoming: Yellowstone Park, September 16. Colorado-Colorado Springs, September 19. Arizona: Huachuca Mountains, October 1.
Egg dates: British Columbia: 4 records, June 16 to July 3.
California: 113 records, April 10 to July 27; 57 records, May 6 to June 17, indicating the height of the season.
Colorado: 16 records, June 4 to July 23; 8 records, June 19 to 27.
Baja California: 3 records, June 21 to July 27.
Washington: 13 records, May 20 to July 25; 7 records, June 6 to 22.
SAN LUCAS FLYCATCHER
EMPIDONAX DIFFICILIS CINERITIUS Brewster
The Lower California race of Eimpidonaa, difficili~ breeds in the mountains of the Cape region of that peninsula and from there northward to the Sierra San Pedro Martir. It was described and named by William Brewster (1888) as a new species, based on a series of some 25 specimens collected by M. A. Frazar at La Laguna. He describes it as “most nearly like F. difficilis but with the general coloring much duller, the upperparts with scarcely a tinge of greenish, no decided yellow beneath, excepting on jugulum and abdomen; wing-bands brownish white.” He says of it elsewhere (1902)
The St. Lucas flycatcher is resident in the Cape Region, where it is not uncommon~ Mr. Frazar found it in the greatest numbers In the Sierras de la Laguna in May and early June. He also obtained specimens at San Jos4 del Rancho in July and at La Paz in February and March. Mr. Bryant has taken it at Comondu, and San Benito and Santa Margarita Islands, while on San Pedro Martir Mr. Anthony found it “very common all over the mountain, especially along the streams and In tha willows. It was evidently nesting” at the time of his “visIt in May, but no eggs were taken.” He also states that it occurs sparingly near the mine and about the mission at San Fernando, where he thinks it nests “in the thick mesquite growth.” It probably replaces B. di.Olciiia In the breeding season throughout the greater part of Lower CalifornIa.
J. S. Rowley has sent me the following notes on his experience with the San Lucas flycatcher: “While camped at La Laguna, atop the Sierra de la Laguna, from May 23 to 28, 1983, I took three sets of four eggs and one set of three eggs, all sets being practically fresh. At this camp a small creek had running water in it at this date, and several pairs of these flycatchers were nesting here. So far as I could see, the nesting habits are the same as the northern race; these nests were all placed behind climbing vines on rocks or in rotted parts of trees, and not more than a few feet from the ground. These little flycatchers were the first to sing in the early dawn and the last to sing at night, seeming to never tire of their liquid-sounding song.”
The eggs are apparently indistinguishable from eggs of the species found in California. The measurements of 12 eggs average 17.2 by 13.3 millimeters; th0 eggs showing the four extremes measure 18.0 by 13.3, 17.3 by 14.3, and 16.3 by 12.3 millimeters.