- 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.
Pacific-slope Flycatcher populations appear stable or slightly declining. The North American Bird Breeding Survey lists these bids together with the very similar Cordilleran Flycatcher, and together the two species' populations showed a small decline between 1966 and 2015. 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 an 11 out of 20 on the Continental Concern Score, and is a U.S-Canada Stewardship species. Pacific-slope Flycatcher is not on the 2016 State of North America's Birds' Watch List.