presupplemental molt, this molt has been fully documented in certain species only recently, having been found in 16 species of North American passerines to date. Natural history Song The sparrow's song sounds like titi-trrrrrrrrrrr, tyew tyew. Only the males sing and the males are known for flying in the air and gliding down while singing which is called "skylarking". Males of the species are one of only a few sparrows known to skylark. The book Heralds of Spring in Texas says that a clue that spring is coming in Midland County, Texas is "the high, sweet trills of Cassin's sparrows". There is also a second flight song with chips which is only from adults when they are on edge. Chicks do a series of sips when they sing. The males sing from February to September with the song of Cassin's sparrow being its most identifiable trait. The Cassin's sparrow's primary song consists of six note complexes, beginning with a soft double or single introductory note, followed by a long, high musical trill on one pitch, and (usually) two lower, well-spaced musical notes, all with a slight minor-key quality. There is enough individual variation in this song that it has been used as a means of identifying individual males in population studies. A secondary song, or "chitter" song, consists of a series of chips, trills, and buzzy notes preceding the primary song. Cassin's sparrows also give a variety of chitter calls and chip notes that have been assigned various roles by different authors, including pair bond maintenance, communication with fledglings, alarm calls, territory defense, etc. Unusual conditions may induce this species to sing at unusual times of year. Territorial males sit in low bushes or grass, or on the ground to sing, but often give spectacular flight-songs. At the beginning of the breeding season, all song is from a stationary, exposed perch and often involves reciprocal proclamation of the primary song among males. Flight songs and skylarking are infrequent until later, in association with the presence of returning females. In flight songs (or skylarking), the territorial male flies up from an exposed perch, such as a bush, to as much as 5 – 10 m in the air, then sings as he glides or flutters down in an arc to a nearby bush or the ground. During the descent, wings are held flat, the head is arched backwards, and the tail