Comments: This species formerly was regarded as conspecific with E. occidentalis (AOU 1998). Johnson and Marten (1988) examined variation in the E. difficilis group and concluded that E. difficilis and E. occidentalis are distinct species. Phillips (1994) argued that existing information does not justify the recognition of E. occidentalis and E. difficilis as distinct species. Johnson (1994) provided additional analyses indicating that E. difficilis and E. occidentalis warrant separate-species status. Form insulicola (Channel Islands flycatcher) may be a distinct species (AOU 1998). Empidonax difficilis, E. occidentalis, and E. flavescens constitute a superspecies(AOU 1998).
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