the sparrow is rarely found in the northern part of its range which might be because of rainfall. The bird's nest is in grass and is a mixture of various weeds and grasses. The female lays from to 3 to 5 eggs. Although Cassin's sparrows use slightly different habitats in different parts of their range, the common denominator across all habitats seems to be that they require both a grass component (usually short grass) and a shrub component. The latter component may be actual shrub species [e.g., mesquite, sage (Artemisia spp.), hackberry (Celtis spp.), rabbitbrush (Chrysothamnus spp.), or oaks (Quercus spp.)] or other vegetative forms that approximate shrub structure [e.g. yucca (Yucca spp.), paddle cacti (Opuntia spp.), ocotillo or bunch grasses]. The need for the structure provided by shrubs or similar plants is related to the bird's need for perches from which to sing or launch itself for its flight song and its frequent use of low shrubs for nest placement. also noted that the mesquite thickets within Cassin's sparrow territories were distinctly preferred when fledglings were present. It appears that relative proportions of grass and shrubs in acceptable Cassin's sparrow habitat cover a wide range from grassland habitats with a very sparse distribution of shrubs to shrubland habitats with a grass cover. Notes References Further reading Theses Gordon CE. Ph.D. (1999). Community ecology and management of wintering grassland sparrows in Arizona. The University of Arizona, United States, Arizona. Groschupf KD. Ph.D. (1983). COMPARATIVE STUDY OF THE VOCALIZATIONS AND SINGING BEHAVIOR OF FOUR AIMOPHILA SPARROWS. Virginia Polytechnic Institute and State University, United States, Virginia. Kirkpatrick CK. M.S. (1999). Trends in grassland bird abundance following prescribed burning in southern Arizona. The University of Arizona, United States, Arizona. Articles Berthelsen PS & Smith LM. (1995). NONGAME BIRD NESTING ON CRP LANDS IN THE TEXAS SOUTHERN HIGH-PLAINS. Journal of Soil and Water Conservation. vol 50, no 6. pp. 672–675. Bock CE & Bock JH. (1992). Response of Birds to Wildfire in Native Versus Exotic Arizona Grassland. Southwestern Naturalist. vol 37, no 1. pp. 73–81. Bock CE & Bock JH. (2002). Numerical response of grassland birds to cattle ranching versus exurban development in southeastern Arizona. Ecological Society of America Annual Meeting Abstracts. vol 87, no 79. Bock CE & Sharf WC. (1995). A nesting population of Cassin's Sparrows in the sandhills of Nebraska. Journal of Field Ornithology. vol 65, no 4. pp. 472–475. Bock