Relationships of the Races of Phaeoprogne Tapera and Their Probable Significance

Abstract

THE genus Phaeoprogne of Baird is confined to South America, ranging from northern Venezuela southward through the Tropical Zone and beyond to the Province of Buenos Aires, Argentina. It contains two forms, a northern and a southern one. For the former, in 1912, 1 proposed the name Phaeoprogne tapera immaculata in the belief the name tapera of Linneus was applicable to the latter. But in 'The Auk' for April, 1929, Mr. W. E. Clyde Todd,' confirming Baird,2 shows the northern bird should be known as tapera Linneus, the southern, as fusca Vieillot. Dr. Hellmayr3 has also reached the same conclusion, and in its fundamental aspects we may, therefore, consider this question of names as nearly settled as such questions ever can be. Mr. Todd, however, calls these birds Phaeoprogne tapera and Phaeoprogne fusca, while I would call them Phaeoprogne tapera tapera and Phaeoprogne tapera fusca. This sounds very much like the difference between tweedledum and tweedledee, but I hope to show the use here of binomials conceals certain significant biological facts to which, so far as nomenclature can, trinomials give expression. Mr. Todd does not hesitate to state in italics these two birds are perfectly distinct species and that their respective ranges overlap over an extensive area. It is my belief, however, these two forms are mutually representative, intergrading races and their breeding ranges overlap only along the line of intergradation. The evidence on which this opinion is based seems to me to be of sufficient importance to warrant presentation. The problem is not a new one to me. In 1917,4 when writing on Colombian birds, I stated I was unable to explain it, but