Cassin's sparrow (Peucaea cassinii) is a medium-sized sparrow. This passerine bird's range is from western Nebraska to north-central Mexico. Taxonomy The first Cassin's sparrow was described in 1852 by Samuel W. Woodhouse from a specimen collected near San Antonio, Texas, and given its species name in honor of John Cassin, a Philadelphia ornithologist. The species was originally known as Zonotrichia cassinii. It was subsequently and variously assigned to the genus Peucaea and eventually to Aimophila around the turn of the century. Much of the confusion seems to have stemmed from a serious lack of knowledge about the anatomy and life history of the species included in the genus. There have been several substantial treatments of the taxonomy of species within the genus Aimophila and a comparison of the song patterns of Aimophila sparrows, but they have focused primarily on evaluating the evolutionary development of these species in order to determine whether this genus actually consists of an unnatural assemblage of species (actually representing several taxonomic groups or divergent forms). None of these publications called into question the placement of Cassin's sparrow within this genus in what is called the "botterii complex" – Botteri's sparrow (Aimophila botterii), Bachman's sparrow (A. aestivalis), and Cassin's sparrow (A. cassinii). In 2010, the American Ornithologists' Union resurrected the genus Peucaea on the basis of genetic, morphological, and vocal data, moving Cassin's sparrow back to Peucaea cassinii. No subspecies or races of Cassin's sparrow are recognized. Description The sparrow has a long tail, gray-brown with white corners, and has dark marks on the back and sides. The species resembles Botteri's sparrow because of its size and marks, but Boterri's sparrow is a weaker shade of gray. The best way to tell the differences between the two is the song of Cassin's sparrow. Both the males and females are the same shade of gray and are 5 to 6 inches, although males are bigger. The Cassin's sparrow is a fairly large, plain, grayish sparrow that lacks conspicuous markings. In flight, the long, roundish tail is obvious and the white tips of the tail feathers are sometimes apparent. This species is most easily identified by its distinctive song and dramatic skylarking behavior during the breeding season. Although often characterized in the literature as secretive and difficult to observe when not singing, observed that Cassin's sparrows readily accommodated the presence of an observer, especially early in the breeding season.