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Overview

Distribution

National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDING: central British Columbia across southern Canada and northern U.S. to New Brunswick, Prince Edward Island, and Nova Scotia, south to southern California, northern Baja California, northern Sonora, southern Arizona and New Mexico, western and central Texas, Arkansas, northern Georgia, and eastern Virginia (AOU 1998). NON-BREEDING: Nayarit and southwestern Oaxaca south to Panama and northwestern Colombia (Stiles and Skutch 1989, AOU 1998).

Subspecies brewsteri: Breeding distribution is west of the Cascades and in the Sierra Nevada from southwestern California to southwestern British Columbia (Sedgwick 2000).

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Physical Description

Size

Length: 15 cm

Weight: 14 grams

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Diagnostic Description

Generally indistinguishable from the Alder Flycatcher (E. ALNORUM), but tends to lack a conspicuous eye ring (Alder tends to have one), have a slightly longer bill, and is less green above (NGS 1983). Reliably distinguished from the Alder Flycatcher only by voice. Song is a sneezy "fitz-bew," with accent on the first syllable (Alder Flycatcher song is "rrree-BEEa" or "fee-bee-o" with accent on the second syllable) (Kaufman 1990, McCabe 1991). Breeding habitats of the two species differ somewhat, with Willow Flycatcher in more southern and western regions of North America and in more open habitats and Alder Flycatcher a more northern bird, generally breeding in shrub and alder thickets of boreal forests in the eastern U.S., Canada, and Alaska (McCabe 1991).

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Ecology

Habitat

Habitat and Ecology

Systems
  • Terrestrial
  • Freshwater
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Comments: BREEDING: Strongly tied to brushy areas of willow (SALIX spp.) and similar shrubs. Found in thickets, open second growth with brush, swamps, wetlands, streamsides, and open woodland (AOU 1983). Common in mountain meadows and along streams; also in brushy upland pastures (especially hawthorn) and orchards (NGS 1983). The presence of water (running water, pools, or saturated soils) and willow, alder (ALNUS spp), or other deciduous riparian shrubs are essential habitat elements (Sanders and Flett 1989, USDA Forest Service 1994). Occurs in both mesic and drier upland conditions, but apparently reaches highest densities on wet sites (Sedgwick and Knopf 1992). It is associated with dense riparian deciduous shrub cover separated by open areas, but large contiguous willow thickets without openings are typically avoided; it does not occur in dense tree cover but will use scattered trees for song and foraging perches and gleaning substrate (USDA Forest Service 1994). Habitat preferences may overlap with alder (EMPIDONAX ALNORUM) and least flycatchers (EMPIDONAX MINIMUS), to include deciduous woods and thickets, bottomlands and swamps (Griggs 1997). Foraging habitat may overlap with western flycatcher (EMPIDONAX DIFFICILIS; Frakes and Johnson 1982).

In southwestern Ontario, generally occurs in more xeric upland sites, but in some areas uses boggy alder thickets, overlapping with alder flycatcher (Barlow and McGillivray 1983). In the Sierra Nevada of California, broad, flat meadows with willows and water are essential (Sanders and Flett 1989). In the Northern Rockies, is apparently restricted to riparian areas with adequate shrub cover (Hutto and Young 1999).

In Colorado, males and females were found to select for different habitat attributes: female-selected nest sites typically had dense willows and were similar in patch size and bush height, male-selected song perch sites were characterized by large central shrubs and high variability in shrub size. On an increasing scale, breeding sites were respectively characterized by greater willow density, larger willow patches with smaller gaps, and greater percent willow coverage than non-willow coverage (Sedgwick and Knopf 1992).

Southwestern willow flycatcher (E. T. EXTIMUS) breeds only in dense riparian vegetation near water or saturated soil. Habitat typically contains dense vegetation in the patch interior, often interspersed with small openings, sparser vegetation, or open water that creates a habitat mosaic of variable density. It nests in shrub and tree thickets 4-7 meters tall, with dense foliage 0-4 meters above the ground, and usually a high canopy coverage (USFWS 1995). The dominant plant species, size and shape of habitat patch, canopy structure and other habitat variables vary from monotypic to mixed-species stands and from simple to complex vegetation structures (Sogge et al. 1997). Habitats include dense high-elevation willow; native broadleaf shrubs and trees composed of willow, cottonwood (POPULUS spp.), boxelder (ACER NEGUNDO), ash (FRAXINUS spp.), alder, or buttonbush (CEPHALANTHUS OCCIDENTALIS); monotypic closed-canopy stands of tamarisk (TAMARIX spp.) or Russian olive (ELAEAGNUS ANGUSTIFOLIA); or a mix of native shrubs and exotic species (Sogge et al. 1997). Along the Virgin River, Utah, is restricted to shrub communities with shrub densities ranging from 70 percent to 100 percent (Whitmore 1977).

NEST SITE: Nests primarily near slow streams, standing water or seeps, swampy thickets, especially of willow and buttonbush (AOU 1983, USDA Forest Service 1994), also dogwood (CORNUS spp.), elderberry, hawthorn, rose, tamarisk, and others; in fork or on horizontal limb of shrub, usually 1-3 meters above ground (see Harris 1991). In montane habitats, nests are usually in willows at least 2 meters high with foliage density of 50-70 percent and about 1 meter of cover above the nest (Sanders and Flett 1989). Also see Sedgwick and Knopf (1992) for information on nest sites and song perches in northcentral Colorado.

Historically, southwestern willow flycatcher primarily in willows, buttonbush, and BACCHARIS spp. with a scattered cottonwood overstory. With changes in riparian plant communities, non-native tamarisk and Russian olive provide nesting habitat in some areas (Brown 1988, USFWS 1995). Along the Colorado in the Grand Canyon, for example, the flycatcher nests in tall tamarisk within 30 meters of water (Brown 1988, Sogge et al. 1997); however it is not known if nesting success differs in tamarisk compared to native vegetation (USFWS 1996). Where E. T. EXTIMUS nests in tamarisk, the tamarisk are usually taller (more than 5 meters) and denser (90 percent canopy closure) than in tamarisk-dominated areas where the flycatcher has been extirpated, and broadleaf shrubs may also be an important part of the community (Sogge et al. 1997).

NON-BREEDING: Uses same types of habitats during migration and winter as breeding season (McCabe 1991). Occurs in dense scrub, deciduous broadleaf forest, streamside gallery forest, and freshwater wetlands (Rappole et al. 1995). In western Mexico and Central America, found in humid to semi-arid scrubby fields with hedges, fences woodland and edge, plantations; frequents low to mid-vegetation levels and often comes into open (Howell and Webb 1995).

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Migration

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Usually arrives on U.S. nesting grounds by May-June (Terres 1980). Present in California from late April to September (Biosystems Analysis 1989). Migrates through southern Arizona mainly in the first half of June and August-September (Phillips et al. 1964). Arrives in Washington in late May or early June. Fairly common migrant in Costa Rica, mid-August to late October (peak late September) and mid-March to late May (Stiles and Skutch 1989). In Ontario, tends to have an earlier and longer migration period in spring than Alder flycatcher (EMPIDONAX ALNORUM), and migrates significantly earlier in fall (Hussell 1991a, 1991b).

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Trophic Strategy

Comments: Eats mainly insects caught in flight; occasionally berries. Bent (1942) states that 96 percent of diet is animal matter, most of which is flying insects. Once fledglings are able to forage for themselves, are less dependent on a localized, concentrated food source (USDA Forest Service 1994).

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General Ecology

BREEDING: Conduct most of their activity within their defended territory, but both male and female will also use adjacent areas, especially when feeding young; territory defense declines once young are fledged (USDA Forest Service 1994). In Ontario, territory size ranged from about 0.1 hectares to 0.47 hectares and averaged 0.35 hectares (Prescott and Middleton 1988); in southern Michigan, territories averaged 0.7 hectares (Walkinshaw 1966). In California, territories ranged from 0.1 hectares to 0.9 hectares, and averaged 0.2 hectares in Fresno County and 0.4 hectares on the Truckee River (USDA Forest Service 1994). Where breeding range overlaps with alder flycatchers (EMPIDONAX ALNORUM), may show territorial defense toward the other species (Prescott 1987).

NON-BREEDING: In Panama, winter home range estimated to be about 1100 square meters (Gorski 1969).

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Life History and Behavior

Life Expectancy

Lifespan, longevity, and ageing

Maximum longevity: 11 years (wild) Observations: One individual was at least 11 years of age when recaptured (http://bna.birds.cornell.edu/).
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Reproduction

A late breeder, eggs usually laid in mid- to late-June and young fledge in August (USDA Forest Service 1994). Clutch size is three to four. Incubation lasts 12-15 days, by female. Young are tended by both parents, leave nest at 12-15 days. Site fidelity strong in both males and females (Walkinshaw 1966). May incur a high rate of cowbird parasitism (e.g., Sedgwick and Knopf 1988, Harris 1991, Brown 1988). Sometimes polygynous and may maintain polygynous trios, possibly a response to narrow habitats with high habitat productivity or other factors (Prescott 1986, Sedgwick and Knopf 1989). Singing, unmated males may be present on breeding grounds, and single pairs may breed in absence of other individuals (USDA Forest Service 1994). On one study in Ohio and Nebraska, 91 nests had 272 eggs from which 99 young fledged (36.4 percent success) and 39.5 percent of nests produced at least one young; 96 eggs and 41 nestlings were depredated (50.4 percent; Holcomb 1972).

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Empidonax traillii

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 3
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2012

Assessor/s
BirdLife International

Reviewer/s
Butchart, S. & Symes, A.

Contributor/s

Justification
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

History
  • Least Concern (LC)
  • Least Concern (LC)
  • Least Concern (LC)
  • Lower Risk/least concern (LR/lc)
  • Lower Risk/least concern (LR/lc)
  • Lower Risk/least concern (LR/lc)
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