Only males sing and the song primarily seems to serve to attract mates and delineate territories. Males sing extensively during the breeding season, but both males and females can give alarm calls in the presence of danger or predators.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
While long term population trends have not been quantified, Pacific-slope flycatchers are a species of Least Concern by the IUCN Redlist. They are not listed under the U.S. Endangered Species act or the Convention on International Trade in Endangered Species. They are listed and protected under the U.S. Migratory Bird Treaty Act. Breeding Bird Survey data show no significant declines of this species between 1966 and 1996.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
There are no known adverse effects of Pacific-slope flycatchers on humans.
Aside from controlling insect populations, there are few other documented benefits to humans.
Positive Impacts: controls pest population
Pacific-slope flycatchers are predators to many insects and spiders and in turn are consumed by hawks, squirrels, snakes, jays, and other predatory birds. They are parasitized by brown-headed cowbirds (Molothrus ater). Aside from this, little else is known about the role of these flycatchers in their ecosystem.
Pacific-slope flycatchers feed almost entirely on insects caught in the air or on tree and bush leaves. They prefer to forage in the middle and lower canopy of forests. They use a hawking method of prey capture; sallying forth from a perch to catch insects on the wing, then returning to the perch. Their main foods are bees, wasps, moths, spiders, flies, and other insects, though they occasionally consume vegetation like blackberry and elderberry leaves.
Animal Foods: insects
Plant Foods: leaves
Primary Diet: carnivore (Insectivore )
Pacific-slope flycatchers winter in southern Mexico from the southern end of Baja California, along the coastal lowlands of the Pacific coast, to Oaxaca. They breed along the Pacific coast, from northern Baja California to southeastern Alaska. Their range stretches east to the Rocky Mountains in British Columbia, the Cascades in Oregon, and the Sierra Nevada mountains in California.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
Pacific-slope flycatchers breed in humid coniferous, dense second-growth, and mixed deciduous-conifer woodlands. They have been found throughout British Columbia, Washington and Oregon in old-growth Douglas fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla), sugar pine (Pinus lam-bertiana), and incense cedar (Calocedrus decurrens) forests. They are associated with shady, riparian habitats. They are primarily found at elevations from 0 to 1500 m. In British Columbia they have been found in red cedar (Thuja plicata) forests, primarily along dense creek vegetation and ravines, often near lakes and ponds. In Mexico, they winter in mountainous conifer forests, tropical deciduous forests, and tropical lowland evergreen forests.
Range elevation: 0 to 1500 m.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: taiga ; forest
Other Habitat Features: riparian
Longest lifespan in the wild is recorded at 6 years based on museum specimens. Longevity in captivity and expected lifespan is unknown
Range lifespan
Status: wild: 6 (high) years.
Average lifespan
Sex: female
Status: wild: 6.0 years.
Pacific-slope flycatchers are small perching birds around 14 to 17 cm in length and with a mass of 9 to 12 g. They have a relatively large head in comparison to their body, with a faint white to yellow teardrop-shaped patch around each eye. They have broad bills with a lower mandible that varies from yellow to light pink, distinguishing them from other flycatchers. Dull olive or brown feathers comprise the upperparts and back, with more pale and yellow feathers beneath. These flycatchers have relatively short wings (60 to 70 mm), longer tails, gray legs, and faint yellow wing bars.
Western flycatcher species (Pacific-slope and Cordilleran flycatcers) are difficult to distinguish from other flycatchers and each other. The olive-green back, almond-shaped pale eye patch, and gray legs differentiate Pacific-slope flycatchers from yellow-bellied flycatchers (Empidonax flaviventris), Acadian flycatchers (Empidonax virescens) and pine flycatchers (Empidonax affinis). The species are further differentiated by song. Pacific-slope flycatchers are indistinguishable from Cordilleran flycatchers (Empidonax occidentalis) in the field and almost impossible in the hand. However, Pacific-slope flycatchers are more often found in lower elevation, humid forests while Cordilleran flycatchers are often found in higher elevations, in dry coniferous forests.
Range mass: 9 to 12 g.
Range length: 140 to 170 mm.
Range wingspan: 60 to 70 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike
Little is known about predation on Pacific-slope flycatchers. However it is likely that they are vulnerable to the main predators of other small, forest birds, including hawks, squirrels, snakes, and jays. Records exist of both Steller's jays (Cyanocitta stelleri) and scrub jays (Aphelocoma californica) preying on Pacific-slope flycatcher nests.
Known Predators:
Pacific-slope flycatchers are mostly monogamous. A single study done on mating Pacific-slope flycatchers in British Columbia reported that 1 in 7 males partnered with 2 females.
Mating System: monogamous ; polygynous
Pacific-slope flycatchers usually hatch several broods in a given breeding season from mid April to mid July. In Monterey County, California they have been found to build nests from April 15 to May 1 for first broods and June 1 to July 15 for second broods and re-nesting. Mean clutch size is four eggs per brood. Incubation time lasts between 13 and 16 days and fledging time is around 14 to 17 days after hatching. Age is presumed to be one year at first breeding and they breed annually afterwards.
Breeding interval: Pacific-slope flycatchers breed once annually.
Breeding season: Pacific-slope flycatchers breed from mid-April through mid-July.
Average eggs per season: 4.
Range time to hatching: 13 to 16 days.
Range fledging age: 14 to 17 days.
Range time to independence: 14 to 17 days.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
The female alone incubates the eggs but both sexes bring food to the fledgling young and remove fecal sacs.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
The Pacific-slope flycatcher, or Empidonax difficilis, is a migratory bird in the Tyrannidae family. Its breeding range covers the humid coniferous forests of the Pacific Northwest and the Pacific coast from southeastern Alaska to Baja California in Mexico. Its yearly migration southward takes the flycatcher through southern Canada and the U.S. states of Washington, Oregon, California, Arizona, and New Mexico to the Pacific coast of Mexico, where it overwinters from northern Baja to a southern extreme of Oaxaca. Rarely does Empidonax difficilis overwinter as far north as California (Kaufmann 2017). It generally lives in wooded areas, and prefers warmth and humidity (All About Birds 2017).
The adult Empidonax difficilis has yellow-olive to olive coloration, with pale yellow lores and brown irises. Its underside is plain and yellowish. When molting, Empidonax difficilis changes relatively few feathers. The coloration of the wings creates two distinct bars, with lighter tips and a darker background. Males are generally more elongated than females, though they typically weigh slightly less. Empidonax difficilis diet consists primarily of insects and other arthropods with some vegetable matter, including blackberry, elderberry, and tarweed (Lowther et al 2016).
Empidonax difficilis is a solitary bird until mating season, during which it is fairly aggressive when on breeding grounds. It gives swift chase while also vocalizing a series of “chrrips” and “bzzt” notes, squeaks, and bill snaps. Near their nests, they have been observed being selectively territorially aggressive, but notably does not attack the California towhee, black-headed grosbeak, or western bluebird (Lowther 2016). They have also been noted to defend their territory against Hammond’s flycatchers (Kaufmann 2017).
Empidonax difficilis usually build their nests on or very near the ground. Nests are assembled entirely by the female and have been observed in the forks of trees, on stumps, within the upturned roots of fallen trees, under bridges, and on rafters in sheds (Lowther et al 2016). A clutch usually consists of 3 or 4 eggs, and are incubated for 13–16 days, during which the female stays in the nest for 75-80% of the incubation period. The nesting period is around 2 ½ weeks and once young leave the nest, they usually remain together for 7-8 days before becoming more dispersed. Empidonax difficilis first reproduce at approximately one year of age and annually thereafter.
Common predators of Empidonax difficilis are very likely similar to those of other small, woodland birds including owls, snakes, and hawks, as well as Steller’s jays and Western screech-owls, though little information exists on this (Lowther et al 2016). When alerted to predators, males give “seet” calls and females sit quietly on their nest (Kaufmann 2017). Though the species is declining in number due to multiple factors such as deforestation and climate change, Empidonax difficilis is classified as “least concern” by the IUCN due to its large population and vast range (Birdlife International 2017). In the state of Washington, however, the bird is listed on the “Audubon Washington Vulnerable Birds List” as “Early Warning” (Seattle Audubon 2017).
The Pacific-slope flycatcher (Empidonax difficilis) is a small insectivorous bird of the family Tyrannidae. It is native to coastal regions of western North America, including the Pacific Ocean and the southern Gulf of California, as far north as British Columbia and southern Alaska, but is replaced in the inland regions by the Cordilleran flycatcher. These two species were classified as a single species, commonly called the western flycatcher, by the American Ornithologists’ Union until 1989.[2] In winter, both species migrate south to Mexico, where they are virtually indistinguishable from one another.
In plumage, the Pacific-slope flycatcher is virtually identical to the Cordilleran flycatcher, and differs only subtly from most Empidonax flycatchers in North America, but its breeding habitat and call are different. Its call can vary slightly by different regions and the bird itself.
The Pacific-slope flycatcher inhabits either coniferous or deciduous forests. In its range it enters mixed woods, Douglas fir forests, redwood forests, and many other wooded environments including riparian woodlands. As of November 2019, there has been one case of these West Coast birds showing up on the East Coast, in Palmyra, New Jersey.[3]
As a flycatcher it will wait on a perch and when it sees a flying insect it will chase it without any apparent effort. They also enter swarms of gnats, mosquitos and wherever such insects congregate. They fulfill an important role in keeping insect populations in check, particularly mosquitoes, and they also eat caterpillars and spiders.
The Pacific-slope flycatcher (Empidonax difficilis) is a small insectivorous bird of the family Tyrannidae. It is native to coastal regions of western North America, including the Pacific Ocean and the southern Gulf of California, as far north as British Columbia and southern Alaska, but is replaced in the inland regions by the Cordilleran flycatcher. These two species were classified as a single species, commonly called the western flycatcher, by the American Ornithologists’ Union until 1989. In winter, both species migrate south to Mexico, where they are virtually indistinguishable from one another.
