Abstract
Before 1965 Cassin’s Sparrow (Aimophila cassinii) had not been documented as a breeding species in Arizona (Philips et al. 1964). In 1965, three nests were found seven miles southeast of Tucson (Ohmart 1966). Since this discovery, Cassin’s Sparrow has been documented as a regular breeder in southeast Arizona grasslands (Monson and Philips 1981). Surveys in the 1990s for the Arizona Breeding Bird Atlas confirmed breeding in Yavapai, Pima, Cochise, and Graham Counties, probable breeding in Santa Cruz County, and possible breeding in Greenlee and Apache Counties (Corman 2005). The summer of 2006 offered an opportunity to observe and document the movement of Cassin’s Sparrow into peripheral habitat areas in southern Arizona. In locations where the grass grew lush among scattered mesquites and cactus, excellent habitat was created for Cassin’s Sparrows. Surveys were conducted in a semidesert grassland area north of Tucson, where Cassin’s Sparrows had neither been reported breeding previously nor reported recently. These observations revealed the presence of many Cassin's Sparrows, including behavior that suggested probable breeding. This is noteworthy as the Arizona Breeding Bird Atlas did not report any signs of possible or probable breeding of Cassin’s Sparrows in Pinal County (Corman 2005).