Cassin's Sparrow Life History

Habitat

Cassin’s Sparrows inhabit dry grasslands with scattered shrubs, cactus, yucca, and small trees such as oak, acacia, mesquite, or hackberry throughout the year, avoiding areas of dense brush or shrubbery. They nest from sea level to about 7,000 feet elevation. They generally do not breed in cultivated fields, with the exception of alfalfa on occasion, and they tend to use native grasslands that are ungrazed and unburned. In the northern parts of their range, Cassin’s Sparrows breed in grassy sandhills with sand sagebrush, rubber rabbitbrush, greasewood, yucca, and prickly pear. In South Texas, they occupy bunchgrass communities with spiny hackberry and prickly pear, while in West Texas they inhabit grasslands with scattered mesquite and juniper. In Arizona and New Mexico, Cassin’s frequent similar grassland habitats as well as desert flats with creosote bush. Migrants and wintering birds select similar habitats throughout the range.

Food

Cassin's Sparrows eat seeds and insects year-round, though the diet consists mostly of seeds in winter. They feed mostly on the ground, moving along by hops, picking up seeds and insects from the ground, picking insects from low vegetation, or stripping seeds or flower buds from plants. During summer especially, they eat many different kinds of grasshoppers, as well as crickets, bugs, caterpillars, ants, bees, wasps, weevils, mantises, and spiders. Among the known plant seeds they consume are chickweed, woodsorrel, sedge, switchgrass, and sorghum.

Nesting

Nest Placement

The nest is set on or near the ground (rarely more than 8 inches above the ground) in a shrub or clump of grass.

Nest Description

The female builds the nest, a loose cup of grasses and weeds lined with hair, fine grasses, and fine roots. Nests average 3.4 inches wide, with interior cup 2.8 inches across and 2.2 inches deep.

Nesting Facts

Behavior

Except for the marvelous conspicuousness of the male’s song flight, Cassin’s Sparrows are rather unobtrusive birds. In this display, a territorial male Cassin's Sparrow flies up to a height of about 20 feet (occasionally 50 feet, singing the quiet first notes of his song. Then he floats down on stiff wings, with tail fanned and legs dangling, while completing the song. Their courtship timing varies regionally. In some parts of the range, pairs form in spring, when males establish territories and pursue females in flight. In other areas, pairs may be established before males begin to sing. Pairs sometimes chase each other in flight around the territory, giving rapid buzzy calls. Males court females while perched in a shrub or on the ground, holding out and fluttering the wings, raising and spreading the tail, and bowing the head, in some cases giving buzzy calls. Male Cassin’s rarely chase or attack other males but do countersing with them at the edges of their territories. Clashes with other sparrows, such as Botteri’s, are also infrequent. They may nest at relatively high densities, but they are not colonial nesters, as they maintain breeding territories, which range in extent from about 0.6 to 12.9 acres. Both male and female share incubation and chick-rearing duties. After fledging, young birds may form small flocks in the nesting area. During the nonbreeding season, Cassin’s Sparrows are also territorial.

Conservation

According to the North American Breeding Bird Survey, Cassin’s Sparrow populations were stable or slightly declining between 1966 and 2015. Partners in Flight estimates a global breeding population of 14 million and rates the species an 11 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. Nevertheless, Partners in Flight estimates that if current population trends continue, the species will lose half its current population by 2086. Conservation threats to the species include clearing of land for development, agriculture, or grazing.

Credits

Dunning Jr., John B., Richard K. Bowers Jr., Sherman J. Suter and Carl E. Bock. (1999). Cassin's Sparrow (Peucaea cassinii), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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