Dusky Flycatcher, Empidonax oberholseri

Dusky Flycatcher, Empidonax oberholseri. Photograph taken within Reserva Monte Mojino, Alamos, Sonora, December 2018. Photograph and identification courtesy of David F Smith, Alamos.

Background and Identification

The Dusky Flycatcher, Empidonax oberholseri, is a member of the Tyrannidae Family of Tyrant Flycatchers. This species is known for its subtle plumage, and therefore, challenging identification. In Mexico, they are called Mosquero Oscuro.

this species has a slim build, with a small bill, a pale eye-ring, and faint wing bars. The upperparts are generally olive-gray, while the underparts are lighter with a grayish wash. During the breeding season, the Dusky Flycatcher is most easily identified by its vocalizations—short, dry “whit” calls and its distinctive song. Like other Empidonax flycatchers, visual identification can be difficult, and distinguishing it from its close relatives often requires careful attention to behavior and habitat, in addition to vocalizations.

Habitat and Geographical Range

The Dusky Flycatcher prefers open woodlands, particularly those dominated by shrubs, such as sagebrush or chaparral, as well as forest edges in aspen, pine, and fir forests. It is often found at higher elevations during the breeding season, typically in the Rocky Mountains, the Sierra Nevada, and the Cascades. Birds that migrate to higher elevations during specific seasons are called altitudinal migrants.

The Dusky Flycatcher is a migratory species. It breeds in montane and subalpine regions of the western United States and southern Canada. During the winter, individuals migrate to the southwestern United States, Mexico, and Central America, inhabiting lower elevation scrub and woodland habitats. It tends to winter in drier areas compared to other Empidonax species.

Common Misidentifications

As with many Empidonax genus flycatchers, the Dusky Flycatcher can easily be confused with other similar species, such as the Gray Flycatcher, Empidonax wrightii, and Hammond’s Flycatcher, Empidonax hammondii. The Gray Flycatcher has a longer tail and a distinctive tail-dipping behavior, which is less pronounced in the Dusky. Hammond’s Flycatcher tends to have a shorter bill and darker overall plumage. Vocalizations are often the most reliable way to distinguish between these species in the field. The Dusky and Hammond’s Flycatchers are so similar that telling them apart is a true challenge. In the field, birders use “primary projection” to distinguish the two species visually: the tips of the primary feathers that stick out past the innermost flight feathers, called tertials, are rather short and stubby in Dusky Flycatcher, and notably longer, narrower, or pointier in Hammond’s.

Conservation Status

From a conservation perspective, the Dusky Flycatcher is categorized by the IUCN as Least Concern. This species has a large range and stable populations across this range.