A practical guide to bird watching in Sonoma County, California

(Unless otherwise indicated, all phone numbers are in the 707 area code)


The latin name of this species (dificilis) suggests the difficulty of identifying flycatchers of the genus Empidonax generally. Sorting out Empidonax flycatchers is the classic identification challenge for birders in North America. These flycatchers can in some cases be virtually impossible to distinguish in the field. Happily, our location eliminates some of the problems. First, Pacific-slope Flycatcher is Sonoma County's only common Empidonax flycatcher, and it's present mostly in the summer months. Most commonly confused here with Willow Flycatcher (Empidonax traillii) during autumn migration, Western Wood Pewee (Cantopus sordidulus), or sometimes even Ruby-crowned Kinglet (Regulus calendula)--see below. Note that older books will refer to this species as "Western Flycatcher," which included what are now considered two separate species: Pacific-slope Flycatcher and Cordilleran Flycatcher (Empidonax occidentalis), the latter with a range far to the east of us (mostly Rocky Mountains, but extending from northern Montana into central Mexico). Pacific-slope Flycatcher usually arrives in Sonoma County from wintering grounds in Mexico by late March and leaves by early October (the bird in the photo below, carrying nesting material, was photographed in Santa Rosa, April 17, 2010). One complication, however, is that stray Cordilleran Flycatchers may very occasionally be present in the area during migration; some birders will insist that during migration we should use the term "Western Flycatcher" unless the two species can be definitively separated--usually by call. The birds don't always call, though, and some observers rightly point out that the calls, too, can be ambiguous. If unsure, it's at least safe to ID your bird as a Western Flycatcher. In truth, however, a stray Cordilleran is likely to go undetected at all. Pacific-slope Flycatcher breeds in most of the county, except the southern extremes.

Small (5-6 inches; 13-15cm), yellowish-green flycatcher. Distinct white (or very pale yellowish) eye-ring with a "broken" look above and a slightly extended, front-to-back oval look; paler and more yellow at the throat and on the breast and belly; darker and more grey-olive on the head, back, wings, and tail; two pale wing bars; upper half of the bill dark, lower half pale orange to pinkish (see photos below), lower mandible color usually conspicuous. Typical upright, alert flycatcher posture and silhouette (with a comparatively broad-looking, slightly crested head). Typical flycatcher behavior--short flights hunting insects followed by perching, often returning to the same perch. Prefers moist, lightly forested areas. Often seen in the lower canopy. Many times identified first by its voice: The call note is a sharp but not-too-loud pseet or an upslurred pseeeeet (the latter sound sometimes described as being J-shaped in pitch--falling slightly before the upslur). Betty Burridge in Sonoma County Breeding Bird Atlas describes the full song used during breeding as a repeated see-wit...s-lit...pik. May also produce a single note that sounds like pik. If you see a small, yellowish-green flycatcher in the late spring to early autumn in Sonoma County with a distinct white eye-ring as described above, it is most likely Pacific-slope Flycatcher.

Experienced birders will find confusion with Ruby-crowned Kinglet puzzling (or amusing), but this is an excellent example of how field guide field marks can lead the inexperienced astray. New birders often simply see a small, olive bird with a white eyering and two white wing bars without noticing what makes the two birds seem so different to experienced birders--mainly, their shapes, postures, and behavior. Although the kinglet may occasionally flycatch, it usually flits nervously from branch to branch looking for food in bushes and trees, often flicking its wings, bending forward, rump in the air, while the flycatcher sits upright--like the flycatcher that it is--and otherwise behaves like a flycatcher, flying out from a perch, catching an insect, and then perching again. Also, most field guides prominently show the kinglet's usually hidden ruby crown, so new birders tend to eliminate the kinglet from consideration if they don't see the red--and the red patch is commonly concealed. Note that Ruby-crowned Kinglet makes a distinctive agitated chattering sound nothing like the vocalizations of Pacific-slope Flycatcher (or any other flycatcher), and that's frequently all that's required to know a kinglet is present (often described as sounding like an old-fashioned typewriter).  

Separating Willow Flycatcher (Empidonax traillii) and Western Wood Pewee (Cantopus sordidulus) from Pacific-Slope Flycatcher can be challenging in large part because the birds usually don't sit still enough to give us the careful looks often required to tell them apart. First, consider Western Wood Pewee: It's generally a little darker, greyer or browner, less green and more drab than Pacific-slope Flycatcher. It's also somewhat larger. Its lower bill will not be all orange/pinkish. The lower bill usually will have color only toward the base (the amount can vary a great deal, but the tip of the lower bill should be dark), and, importantly, the pewee lacks the white eye-ring, as does Willow Flycatcher, although both of those birds may have a suggestion of an eyering. Western Wood Pewee is also somewhat paler at the throat and lower belly with dusky grey on the flanks often described as making it appear to be wearing a vest. Voice may be a help (see links below). Pewees tend to sit still while looking for insects. Pacific-slope and other Empidonax flycatchers are fidgety, often flicking their tails.

Willow Flycatcher is the only Empidonax flycatcher likely to cause confusion, but it is a much less-common bird in Sonoma County, and usually present only during autumn migration (typically between mid-August and early October--although according to some sources it has been noted during the spring migration on a few occasions in surrounding counties). Tends to stay closer to the coast. Note that Willow Flycatcher may have a suggestion of an eyering, or it may have none at all, but it does not have the prominent oval eyering of Pacific-slope Flycatcher (or Cordilleran Flycatcher).

Further reading:

Bolander and Parmeter, Birds of Sonoma County California, rev. ed., 2000, p. 82

Brinkley, National Wildlife Federation Field Guide to Birds of North America, 2007, p. 309

Burridge, ed., Sonoma County Breeding Bird Atlas, 1995, p. 101

Dunn and Alderfer, eds., National Geographic Field Guide to the Birds of North America, 5th ed., 2006, p. 300

Dunn and Alderfer, eds., National Geographic Field Guide to the Birds of North America, 6th ed., 2011, p. 328

Dunne, Pete Dunne’s Essential Field Guide Companion, 2006, p. 403

Ehrlich, Dobkin, and Wheye, The Birder's Handbook, paperback edition, 1988, p. 390 (as "Western Flycatcher")

Fix and Bezener, Birds of Northern California, 2000, p. 246

Floyd, Smithsonian Field Guide to the Birds of North America, 2008, p. 287

Kaufman, Field Guide to Birds of North America, 2000, p. 246 (listed together with Cordilleran as Western Flycatcher)

Kaufman, Advanced Birding, 1990, pp. 184, 1999-2011, 210-211

Kaufman, Field Guide to Advanced Birding, 2011, pp. 347-387 (notes on Empidonax flycatchers generally), 351, 381

Lukas, Bay Area Birds: From Sonoma County to Monterey Bay, 2012, p. 178-179

Parmeter and Wight, Birds of Sonoma County California, Update (2000-2010), 2012, p. 49

Peterson, Field Guide to Birds of Western North America, 4th ed., 2010, p. 246

Peterson, Western Birds, 3rd ed., 1990,  p. 240 (as "Western Flycatcher")

Sibley, Field Guide to Birds of Western North America,1st ed., 2003, pp. 276, 284

Stokes, Stokes Field Guide to the Birds of North America, 1st ed., 2010, p. 466

Vuilleumier, American Museum of Natural History, Birds of North America: Western Region, 2011, p. 255

Voice: Cornell Lab of Ornithology: All About Birds--Pacific-slope Flycatcher*

Voice: Cornell Lab of Ornithology: All About Birds--Willow Flycatcher

Voice: Cornell Lab of Ornithology: All About Birds--Western Wood Pewee

*Note that, to my ear, the recording on this page does not sound like the voice I'm used to hearing locally, but its thin, high-pitched quality contrasting with the buzzy, two-note Fitz-byew of Willow Flycatcher does provide a useful feel for the general difference in the voices of these two birds. Once you've heard the local Pacific-slope Flycatcher it's easy to recognize. Try to see and hear one for yourself with an experienced local birder.




© Colin Talcroft, 2009, 2010, 2011, 2012, 2013

Unless noted, all photos by the author. If you would like to use one of my images, please ask for permission for non-commercial use with proper credit or commercial use with proper compensation.


Pacific-slope Flycatcher, Medica Rd., Santa Rosa, April 22, 2010

For comparison: Western Wood Pewee, Spring Lake, Santa Rosa, September 17, 2012

Pacific-slope Flycatcher, Spring Lake, Santa Rosa, May 14, 2013

Pacific-slope Flycatcher

Empidonax difficilis

1990-2013 Sonoma County data. Graph provided by eBird (www.ebird.org), generated July 29, 2013

EBird reported occurrence in Sonoma County