The western wood pewee (Contopus sordidulus) and Pacific-slope flycatcher (Empidonax difficilis) are two similar-looking bird species found in western North America. They belong to different genera but occupy similar ecological niches. Both are small tyrant flycatchers that feed on flying insects and breed in forested areas. However, there are some key differences between these two species in terms of appearance, voice, habitat, and range.
Appearance
The western wood pewee and Pacific-slope flycatcher can be very tricky to distinguish by sight alone. They are both relatively small songbirds, measuring 15–19 cm in length with wingspans around 30 cm. Their plumage is overall drab grayish-olive above and pale yellowish below.
Some key differences in appearance that can help identify the species include:
Bill shape
– Western wood pewee: Longer, wider bill. The upper mandible is dark and the lower mandible is pale yellowish.
– Pacific-slope flycatcher: Shorter, more slender bill. Both mandibles are dark.
Eye ring
– Western wood pewee: Has a faint narrow eye ring.
– Pacific-slope flycatcher: Has a more distinct white eye ring.
Wing bars
– Western wood pewee: Two distinct buffy wing bars.
– Pacific-slope flycatcher: Fainter, less noticeable wing bars.
Primary extension
– Western wood pewee: Longer primary wing feathers giving a slightly more elongated wingtip.
– Pacific-slope flycatcher: Shorter primary extension so wings do not appear elongated.
Feature | Western Wood Pewee | Pacific-Slope Flycatcher |
---|---|---|
Bill shape | Long, wide bill with pale lower mandible | Short, slender dark bill |
Eye ring | Faint narrow eye ring | More distinct white eye ring |
Wing bars | Two distinct buffy wing bars | Fainter, less noticeable wing bars |
Primary extension | Longer primaries, elongated wingtips | Shorter primaries, no wing elongation |
Voice
The calls and songs of the western wood pewee and Pacific-slope flycatcher are very different and provide the most reliable way to distinguish these species in the field.
Western wood pewee song
The song of the western wood pewee is a plaintive, rising “pee-EEEE” or “pee-err.” The first note is lower and rises sharply to a clear, whistled second note. Songs are typically given repeatedly from an open perch.
Pacific-slope flycatcher song
The Pacific-slope flycatcher delivers a buzzy “beep” or “wit” song, often described as sounding like a squeaky toy. The song lacks the clear whistled notes of the western wood pewee.
Calls
The call notes also differ. Western wood pewees give a soft, whistled “peeer.” Pacific-slope flycatchers have a harsher “pit” or “whit” call.
Habitat
The western wood pewee and Pacific-slope flycatcher occupy broadly similar forest and woodland habitats across their respective ranges. However, there are some habitat preferences that differ between the species:
Western wood pewee
– Favors open, drier forests and woodlands.
– Often found in ponderosa pine, oak, and pinyon-juniper woodlands.
– Occurs at lower elevations on forest edges and clearings.
Pacific-slope flycatcher
– Prefers denser, wetter forest habitats.
– Common in Douglas fir, redwood, and mixed conifer forests.
– More likely to occupy higher elevations and interior forest areas.
So while both occur in western woodlands, the western wood pewee tends to prefer more open and drier areas compared to the Pacific-slope flycatcher’s preference for dense, damp habitats.
Range and Distribution
The breeding ranges of these species show some overlap but also some key differences:
Western wood pewee
The western wood pewee breeds from southern British Columbia through the western United States to Baja California and western Texas. It winters in Mexico and Central America.
Pacific-slope flycatcher
The Pacific-slope flycatcher breeds along the Pacific Coast from southeast Alaska through British Columbia to California. It winters in Mexico and Central America.
So while their breeding ranges overlap in the Pacific Northwest, the Pacific-slope flycatcher has a more northerly range overall along the coast. The western wood pewee extends further east and south into the interior western states.
Range | Western Wood Pewee | Pacific-Slope Flycatcher |
---|---|---|
Breeding | Southern BC to CA, west TX | Southeast AK to CA |
Wintering | Mexico, Central America | Mexico, Central America |
Behavior and Ecology
As small insectivorous birds occupying similar habitats, the behavior and ecology of these two flycatchers is fairly similar in many respects:
– Both are aerial insectivores, catching insects (and sometimes berries) on the wing.
– They feed by perching on open branches and flying out to snatch insects, returning to the same perch.
– They are agile flyers with quick, acrobatic maneuvers to grab prey.
– They nest in similar sites, building small cup nests on horizontal tree branches.
– Clutch sizes are typically around 3-4 eggs for both species.
However, some subtle differences in their foraging and breeding behavior exist:
– The western wood pewee prefers more open areas for flycatching and is more likely to use lone, dead trees or poles as perches.
– The Pacific-slope flycatcher is more of an interior forest species that prefers catching insects amid denser foliage.
– Pacific-slope flycatchers may occasionally hover-glean insects from foliage, a behavior rarely seen in western wood pewees.
– Western wood pewees are slightly more migratory, traveling longer distances, compared to the shorter-distance migration of Pacific-slope flycatchers.
So while the general natural history is similar, the western wood pewee exhibits some more open-country foraging habits compared to the forest-adapted Pacific-slope flycatcher.
Taxonomy
The western wood pewee and Pacific-slope flycatcher are classified in different genuses:
– The western wood pewee is in the genus Contopus. This genus contains around 12 species of pewees and phoebes found mostly in the Americas.
– The Pacific-slope flycatcher is in the genus Empidonax. This is a speciose genus with around 15 species of empid flycatchers, most breeding in North America.
Previous taxonomic treatments placed both species in the genus Empidonax. However, phylogenetic studies based on DNA sequencing found that the western wood pewee was distinct enough genetically to warrant placement in its own genus, Contopus.
Within the family Tyrannidae (tyrant flycatchers), recent phylogenetic analyses place Contopus and Empidonax in different subfamilies:
– Contopus is placed in the subfamily Tyranninae, along with kingbirds and tropical species like the bright yellow eastern wood pewee.
– Empidonax remains in the subfamily Fluvicolinae, which contains many drably colored, cryptic flycatchers like the alder flycatcher and least flycatcher.
This taxonomic division reflects the evolutionary divergence between these two flycatcher groups. While superficially similar, they have followed different evolutionary pathways.
Identification Tips
To quickly summarize the main identification points:
Western Wood Pewee
– Song: Rising “pee-EEEEE”
– Call: whistled “peeer”
– Long wide bill with pale lower mandible
– Elongated wingtips
– Favors open, drier woodlands
Pacific-Slope Flycatcher
– Song: Buzzy “beep” or “wit”
– Call: harsh “pit” or “whit”
– Short dark bill
– No wing elongation
– Prefers wetter, dense forests
Listen for the very different songs and calls. Also check bill length and shape along with subtle differences in wingtips. Habitat can provide additional clues, with the western wood pewee in more open, drier areas. With some practice, most sightings can be confidently assigned to species in the field.
Conclusion
While the western wood pewee and Pacific-slope flycatcher occupy similar ecological roles, they can be reliably distinguished by differences in vocalizations, morphology, habitat preferences, and range. Listen and look closely when encountering these species to pick up on their distinctive traits. Proper identification may require patience and practice as their appearance is so similar. But with careful observation and attention to details like song, bill shape, eye rings, and wingtips, even tricky empid flycatchers can be confidently identified.