The Races of Empidonax affinis

Abstract

SEVERAL years ago the writer had occasion to study the extent of post-mortem color change in the Wright's Flycatcher (Empidonax oberholseri).l For this purpose he borrowed from the Biological Survey a small series, among which was an unusually large Jaliscan specimen concerning which his notes remark possibly E. pulverius?. As he had never seen a specimen of any race of affinis, the matter was not then investigated. In 1941, however, in the course of reviewing the Biological Survey collections in Washington, the same specimen again attracted attention. Comparison soon showed that it was indeed a member of the affinis group, but rather different in color. It was also at once evident that Vera Cruz specimens of supposed 'affinis,' examined in the meantime, had been far from that race in dorsal coloration. Since even trepidus has been recently regarded as a mere intergrade between affinis and pulverius, it was decided to make a thorough review of the species. For the use and loan of specimens in this study, I am indebted to the authorities of the United States National Museum, Fish and Wildlife Service, Carnegie Museum, and American Museum of Natural History. In the material examined, there appear to be six races, which may be recognized as follows: