- 5.5–6.7 in
- 7.9–9.1 in
- 0.3–0.4 oz
- Western Flycatcher (in part)
- Moucherolle côtier (French)
- Mosquero californiano (Spanish)
- The population of Pacific-slope Flycatcher breeding on the Channel Islands off southern California may actually be best treated as a distinct species. It is larger than mainland populations, has a longer bill, a paler chest, slightly different vocalizations, and differs genetically.
- The scientific name of the Pacific-slope Flycatcher, difficilis, is appropriate. It means "difficult," and this species is extremely difficult to distinguish from the similar Cordilleran Flycatcher.
Warm, humid lowland coniferous forest, pine-oak forest, and dense second-growth woodland.
Insects caught in the air or gleaned from foliage of trees and shrubs.
There is little information on Pacific-slope Flycatcher population trends, but populations appear stable or slightly declining. Partners in Flight estimates a global breeding population of 7.4 million birds, with 68% breeding in the U.S., 32% breeding in Canada, and 100% wintering in Mexico. The species rates a 12 out of 20 on the Continental Concern Score, and is a U.S-Canada Stewardship species. Pacific-slope Flycatcher is not on the 2014 State of the Birds Watch List.
- Lowther, P. E. 2000. Pacific-slope Flycatcher (Empidonax difficilis) and Cordilleran Flycatcher (Empidonax occidentalis). In The Birds of North America, No. 556 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
- North American Bird Conservation Initiative, U.S. Committee. 2014. State of the Birds 2014 Report. U.S. Department of Interior, Washington, DC.
- Partners in Flight. 2012. Species assessment database.