Swainson's Flycatcher (Myiarchus swainsoni) - HBW 9, p. 432

Taxonomy: M[yiarchus] Swainsoni Cabanis and Heine, 1859, Rio de Janeiro, Brazil.
A taxonomically difficult complex; in need of revision that carefully integrates molecular and morphological data. Nominate race is larger and/or darker than most others, also differs vocally, and phylogenetic analysis of mitochondrial DNA indicates that it is not closely related to other races; almost certainly represents a separate species. From mtDNA studies, other races appear extraordinarily closely related to each other (although phaeonotus not included in samples), and also closer to M. tuberculifer and M. barbirostris than to all other taxa in genus (as mirrored in voice-playback experiments). Hypothesis that variation between races pelzelni and ferocior (possibly including phaeonotus) is clinal, with increase in size and increasingly paler upperparts from N to S, needs to be tested. Phenotypic intergradation occurs between nominate and ferocior, but at mtDNA level this is unidirectional, and hitherto only mtDNA from latter taxon recorded in zone of morphological intergradation. Field and laboratory studies needed. Birds from N sandy savanna of Surinam described as a further race, albimarginatus, but characters appear attributable to fresh-plumaged intergrades between phaeonotus and pelzelni. Notably, two such intergrade specimens from nearby Guyanan savannas have highly divergent mtDNA; further study required. Four subspecies currently recognized.