Cassin's Sparrow

Peucaea cassinii


Distribution, Migration, and Habitat

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Figure 1. Distribution of Cassin's Sparrow.

Winter status in many areas is poorly known. Limits of this species’ breeding range fluctuate in response to rainfall levels, and singing males may appear north of the distribution shown when greater than average rainfall produces lush vegetative growth in normally arid shrub grasslands.

eBird range map for Cassin's Sparrow

Generated from eBird observations (Year-Round, 1900-present)

Figure 2. Annual cycle of breeding, migration, and molt in se. Arizona.

For Cassin’s Sparrow populations in southeastern Arizona.

Example of Cassin's Sparrow habitat in Arizona.

Arid grasslands with scattered shrubs, yuccas, or low trees such as mesquites and oak. Near thickly vegetated draws, prefers open slopes, rarely going into dense brush.

© Paul Suchanek , Arizona , United States , 29 December 2016
Cassin's Sparrow on Opuntia cactus.

Habitat in breeding range also includes ground layers dominated by grasses, or forbs and cactus (Opuntia spp.) in overgrazed areas.

© Drew Beamer , Colorado , United States , 17 August 2017
Example of Cassin's Sparrow habitat in Texas.
© Justin LeClaire , Texas , United States , 19 March 2017

Distribution in the Americas

Breeding Range

Figure 1. Arid and shrubby grasslands from central and eastern Colorado (52), southeastern Wyoming (53), western Nebraska (54), southwestern Kansas (55), south through western Oklahoma (56), central and western Texas (largely absent east of 97° W) (57), eastern and southern New Mexico (58), and southeastern and central Arizona (59). In Mexico, north-central Sonora, and from northern and eastern Chihuahua, northern Coahuila, northern Nuevo León, and northern Tamaulipas south to northern Zacatecas and southern Tamaulipas (24, 60, 61). Erratic in distribution along edges of range; present in some summers in southeastern Wyoming, western Nebraska, western Arizona. For example, in Arizona normal breeding range extends west to Baboquivari Mountains. and north to San Carlos Indian Reservation (62). In years of exceptional summer rains, Arizona range has extended west to Growler Mountains (1959), Yuma County (1961), Painted Rock Reservoir, Maricopa County (1974), and Sells, Pima County (1978). Similarly, in adjacent Sonora, Mexico, can be found in spring west in rainy years to Caborca and Puerto Penasco (61). In northern Arizona, only one record near New Mexico border: eastern Apache County, June 1976 (62).

Common summer resident in Big Bend region, Texas, in wet years, but may be completely absent in dry years (63). Sporadic breeder within Big Bend National Park, Texas.

Present in numbers (15 singing males in 1978, 4 singing males in 1993) in potential breeding habitat in the Lanfair Valley of eastern San Bernadino County, California. In both years, heavy winter rains stimulated lush growth of desert annuals, which may have attracted the males (64, 65); no evidence of breeding in either year.

Overwintering Range

Imperfectly known due to difficulty in detecting birds other than singing males. Fairly common to uncommon in U.S. in southern two-thirds of Texas breeding range and southeastern Arizona. Few winter records from southern half of New Mexico; Hubbard (4) presumed that wintering was rare in that state. Also winters throughout Mexican portion of breeding range with some also wintering south of the breeding range from northern Sonora south along Pacific slope to northern Nayarit, and in the interior from northern Zacatecas and northern San Luis Potosí south to Guanajuato (24, 60, 61, 66). Occasionally found south to Colima and Jalisco (RKB). Very scarce in Texas north of 33°N (20). Local winter abundance may be related to grass seed production, resulting from summer rains (67).

Other Records

Multiple records in Ontario, including at least 5 reports from Point Pelee National Park (68). Multiple records also from Utah (69), Nevada (70), Indiana (71, 72). Vagrant records from a wide variety of additional locations, including northern Baja California (24) and Ardmore, South Dakota, as well as locations in the eastern half of North America (e.g., Camden, Missouri; Island Beach State Park, New Jersey; Chicago, Illinois; Mount Desert Island, Maine and Seal Island, Nova Scotia [73, 74, 75, 60]).

Associated with the following Neotropical zoogeographic regions by Stotz et al. (76): Baja-Sonoran, Mexican Plateau, Gulf-Caribbean Coast, in northern temperate grasslands, and arid lowland scrub.

Distribution Outside the Americas

Not recorded.

Nature of Migration

A short-distance, partial migrant, but the nature of its movements are complex and poorly understood, in part because of difficulty in detecting species when males not singing or displaying.

Timing and Routes of Migration

Patterns of Movement

Migratory in the northern portion of its breeding range, but migration behavior and even migratory/winter status of species is poorly known in many areas, due to secretive nature of nonsinging birds. Latest records in some areas reflect only when males stop singing, not when birds depart. For instance, Hubbard (4) reported latest specimens for eastern New Mexico were collected 26 October and 16 November, but last sight records were in late July. In western New Mexico, last specimen records were in late September (5 specimens from 1937 to 1972). In southeastern Arizona, the increase in density of singing males during August may be part of a movement of birds from eastern part of range (3, CEB). Although several authors have suggested that some individuals may be breeding in different geographic areas within a single year as part of this movement, this hypothesis remains unproven.

Patterns of residency and movement complex in western Texas. In El Paso area (El Paso County and vicinity), J. Donaldson and B. Zimmer (personal communication) summarize species status as in Table 1. Unclear whether periods of presumed absence (early summer, early winter) indicate actual migration from area, or difficulty of finding birds when not territorial and singing. However, much field work during these periods failed to find any birds. If migratory, unknown where these birds go, or where arriving birds (mid July, late December) come from.

Similar confusing pattern of residency and migration in southeastern Arizona. Phillips (5: 412) claimed that Cassin's did not breed in Arizona, but instead "appear in Arizona in mid July as an abundant fall transient, having migrated west from the southern Great Plains." He presented no evidence to back up this claim that Great Plains was the source of Arizona summer residents. Breeding first documented in southeastern Arizona in 1965 (77). It is now known that Cassin's Sparrows in southeastern Arizona breed from July–September in all but extremely dry years. Schnase (29) argued that it is unlikely that birds from west-central Texas participate in movements to Arizona as suggested by Phillips (5). Differences in song structure and winter distributions suggest populations in Great Plains and in Arizona are separate (S. M. Russell, personal communication).

Banding of breeding and wintering Cassin's at small desert grassland (Wilmot Cienega) near Tucson, Arizona, illustrates the confusing patterns (unpublished study by RKB). In this area, wintering sparrows were conspicuous in early 1980s on small winter territories from October, and began singing during March–late April. The sparrows then essentially disappeared because males stopped singing; no response to broadcast of songs and few mistnet captures were obtained in May and early June. With the onset of summer rains (usually in early July), males began singing again, and the sparrows bred in large numbers. Banding in winter and summer determined that none of the wintering birds were part of the late summer breeding population. In fact, none of the winter-banded birds were caught the following winter, although one color-marked bird was resighted. Summer-captured birds also were not observed or captured in following winter. Thus, breeding and wintering populations at this location were separate, or all birds showed low philopatry.

Banding results in this study are consistent with the suggestion of possibly nomadic movements between summer and winter seasons, rather than typical passerine pattern of high philopatry to previously held territories. Alternatively, birds may have regular seasonal migration south in winter, north in summer, but weak philopatry on local scale. Cassin's Sparrow in Texas may have higher philopatry, since Schnase (29) documented between-year return of several males to previously occupied territories using distinctive song characteristics for each male.


First records in spring include (all dates from Hubbard [4] unless otherwise noted): Kansas, 29 April; Oklahoma, 24 March; Texas, 24 February (Rockport), 26 March (Amarillo; K. Seyffert, personal communication), 5 April (Midland), 26 May (New Lincoln County, 78); New Mexico, 27 May (78). Extreme dates may be less informative than general patterns. For instance, although 26 March is record arrival date in Amarillo, typical arrival date there is 21 April (K. Seyffert, personal communication). In western Oklahoma, general pattern is that birds arrive in early April; quiet birds, possibly females, are first observed early May (J. Grzybowski, personal communication).

In southeastern Arizona, wintering birds leave late April–early May; latest spring record 14 May (5). In Sonora, Mexico, wintering specimens taken as late as 27 March, 1 April at Guirocoba (4), while singing birds taken in "late March and early April" (61: 287) in western Sonora could have been wintering or spring migrants.


Last records in fall include (all dates from Hubbard [4] unless otherwise noted): Oklahoma, 21 November; Texas, 2 October (78), Amarillo 27 September (K. Seyffert, personal communication); New Mexico, 16 November (east) and 30 September (west). Again, late dates may be less informative than general patterns; J. Grzybowski (personal communication) considers mid to late September to be more typical pattern for fall migration in western Oklahoma, not 21 November date reported above. However, few observations in fall for Oklahoma (J. Grzybowski, personal communication).

Near Big Bend, Texas, a distinct wave of fall migrants during the first week of September, usually ended by 20 September (63). Extralimital fall dates include birds at Austin, Texas, on 3 November 1920 and 1 December 1889 (79).


Gordon (80) found that Cassin’s Sparrow and Grasshopper Sparrow were the most sedentary species in the overwintering sparrow community in southeastern Arizona grasslands. Likelihood of movement to different patches is low and constant throughout winter, indicating strong tendency to remain in fixed home-range.

California Records

Vagrant birds are reported most frequently from California: Farallon Island (12 records in June, July, September, October); Little River mouth (Humboldt County, 81); Mono Lake (82); El Cajon (3 records) (83, 84); northern end of Salton Sea (84); and Death Valley Junction (85).

Migratory Behavior

Little studied. Five sparrows captured in late March 1984, and held in rooftop cages in Tucson, Arizona, through early April showed little evidence of Zugunruhe, or migratory restlessness (night-time activity that corresponds with the time birds regularly undertake migratory flight). Cages were paper-lined cones with open-mesh tops and ink pads in the bottom ("Emlen funnels"). Birds could see the night sky through the open mesh. Orientation and intensity of Zugunruhe was recorded by analyzing the ink marking made by birds when they attempted to walk up paper cone. Vector lengths of ink tracings made in these cages during night-time activity averaged 0.127 (range 0.022–0.381), shorter than those of long-distance migrants such as Savannah Sparrow (Passerculus sandwichensis, 0.802 and 0.618) (86). Short vector-lengths argue against a long distance migration, as Berthold (87) found that degree of Zugunruhe (as measured by vector lengths) correlated with distance of migration for 6 species of Sylvia warblers. Collectively, this suggests that Cassin's Sparrows near Tucson were making a short seasonal movement in late April.

Emlen cage studies also were used to identify the direction of spring movement of captured sparrows in Tucson (RKB). Sparrows were monitored during day in rooftop cages that gave birds a view of the sky, and at night in a planetarium at the University of Arizona in Tucson. An orientation of about 120° would direct migrating birds towards the center of the species' range, while a 180° orientation would reflect southward migration. Mean azimuth of migratory direction over all trials was 151°. Mean direction of nocturnal trials was 169°, diurnal trials 103°. Individual birds showed mean azimuths ranging from 95.6 to 245° (each individual mean is the average of 4–14 trials). Mean direction of nocturnal trials (and all trials combined) leads to northern Sonora, diurnal trials indicate flight toward western Texas or southwestern New Mexico. New Mexico is unlikely destination as extremely few April or May records exist for this species in southwestern New Mexico. Evidence not conclusive but suggests birds in this area are not long-distance migrants (i.e., from Great Plains), but exhibit short, seasonal movement to south or east. Firmer conclusions may require satellite-tracking of marked birds, a study currently at the edge of existing technology.

Control and Physiology of Migration

Experiments using Emlen funnels suggested that this species can orient to both sun and stars (RKB). Three of 5 birds increased weight during Zugunruhe experiments by putting on subcutaneous fat, although weight increases were modest (2.0, 4.0, 5.0 g) and could have been due to food availability in captivity.

Of free-ranging Cassin's Sparrows banded at Wilmot Cienega in southeastern Arizona, 4 of 5 individuals caught 19–22 April 1983 had visible subcutaneous fat. No birds caught from October to March at same site had visible fat. Only 1 of 10 marked Cassin's Sparrows remained on territory by 28 April 1983 (territoriality determined by repeated observation of marked birds and response to song broadcasts). No individuals were observed at this site from 29 May to 10 June 1983 (RKB, JBD).

Habitat in Breeding Range

Figure 2. Arid grasslands with scattered shrubs, yucca, or low trees such as mesquite (Prosopis) and oak (Quercus). Near thickly vegetated draws, prefers open slopes, rarely going into dense brush (78). Also in ground layers dominated by grasses (Poaceae), or forbs and cactus (Opuntia spp.) in overgrazed areas (3).

Occupied locations in Texas varied from sea level to 1,540 m, while sites as high as 2,150 m occupied in Colorado (88). Near Austin, Texas, uses mesquite thickets and gravel flats dotted with chaparral with fragrant Catclaw Acacia (Senegalia greggii); avoids dense chaparral (79). Along the southern Texas coast, sympatric with Botteri's Sparrow in tall bunchgrass (20). Near Rio Grande delta, restricted to more xeric habitats with Opuntia and Spiny Hackberry (Celtis ehrenbergiana). In the Davis Mountains of western Texas, occupies juniper (Juniperus)/mesquite/grass ecotone (3).

In Colorado, found in Rubber Rabbitbrush (Ericameria nauseosa) grasslands in Logan County, and along South Platte River. Common grasses in this area include brome grass (Bromus spp.), three awn (Aristida spp.), needlegrass (Stipa spp.) (89). In Nebraska sandhills, mixed-grass prairie with scattered yucca (Yucca spp.), especially along ungrazed roadsides (54). First records for Wyoming (90) were in rolling sandhills with relief averaging 15 m tall; total vegetation cover about 60%, with Sand Sagebrush (Artemesia filifolia), Greasewood (Sarcobatus vermiculatus), yuccas, Opuntia cacti and grasses (Andropogon and Muhlenbergia spp.). Similar habitat used in Colorado and Nebraska.

In southeastern Arizona, occupies extensive mesquite grasslands and other weedy or grassy habitats in Lower and Upper Sonoran Zones (62). Prefers lightly grazed or ungrazed upland grasslands over heavily grazed grasslands (14, 12, 67). In ungrazed southeastern Arizona site, Cassin's Sparrow was most common on level upland mesquite-grassland, while Rufous-crowned Sparrow was more common on slopes and ravines, and Botteri's Sparrow was abundant in bottomlands dominated by Big Sacaton (Sporobolus wrightii) (KB, JBD, 91). At same site, Cassin's most abundant in unburned native grasslands with 50% canopy cover, avoiding burned areas for 2 years post-fire (13), and also rare in uplands dominated by exotic African bunchgrasses (Eragrostis spp.) (92). Near Tucson, Arizona, occupies grassy cienegas within lowland desert flats otherwise dominated by Creosote Bush (Larrea tridentata) (RKB, JBD).

Habitats used in Mexico are poorly described. In Sonora, presumed breeding populations concentrated in mesquite grasslands in northern portion of state, but no confirmed breeding records (61). In Chihuahua, occupies tussock grasslands with scattered mesquite, Catclaw Acacia, Desert Willow (Chilopsis linearis), and dry composites. Near Monterrey, singing in March in thorn scrub habitat at about 460 m (93; J. Hubbard in Wolf [3]). In San Luis Potosí, a male in full breeding condition was collected 10 July 1952 in “mesquite grassland with a good growth of new grass” at 1,800 m (94: 269). Urban (95) collected Cassin's Sparrows in breeding condition from several locations near Saltillo, Coahuila, but did not describe the habitat.

Avoids most agricultural fields but has been reported in alfalfa during June in Colfax County, New Mexico (4) and in early June near Kenton, Oklahoma (M. M. Nice in Williams and LeSarrier [78]).

Habitat in Migration

Little information, but seems to prefer habitats similar to breeding grounds. During fall in Texas uses brushy draws and canyons, Opuntia stands and brush lining the edges of grassy savannas (20). A single individual near Willis, New Mexico, was taken in fall 1883 at an elevation of 2,400 m (78). No information on spring migration. Singing males that occur in unusual habitats (e.g., dunes along the beach at Puerto Penasco, Sonora) may have been spring migrants (61).

Habitat in the Overwintering Range

Same as breeding habitat. At Big Bend National Park, Texas, wintering birds usually found in weedy spots along the Rio Grande, such as old fields in Rio Grande Village (63). Chisos Mountains Christmas Bird Count recorded 58 birds in 1968, suggesting that the species can be common in western Texas in winter (63). In southeastern Arizona, common in ungrazed grasslands but missing from adjacent grazed site (96, 67).

In Sonora, large numbers may occur in dense grasslands with scattered shrubs and little or no cattle grazing, especially south of Hermosillo (61). At least 100 individuals were found in a single ungrazed pasture in southern Sonora one year following a summer of abundant rainfall; none were present in other winters when pasture was grazed (61). North of Mazatlán, Sinaloa, Mexico, 6 individuals responded to song broadcast from weedy/grassy patches within 0.5 km of beach (S. M. Russell, personal communication).

In Chihuahua, Cassin's Sparrow winters in desert grasslands where abundant as breeder (66). Occurrence strongly and positively related to grass cover and grass height, also significantly increasing with increased shrubland habitat area. Negatively related to interaction between grass height and tall shrub density. In this region, about 30 km2 converted to farms from 2005–2008 at one of two main study sites (66).

Historical Changes to the Distribution

Cited by Johnson (97) as 1 of 14 species that expanded north from Mexico or southwestern U.S. since 1950s, perhaps responding to decadal cycle of increasing rainfall outside of previous range.

May be present some years but absent in others in areas along edges of breeding range, while abundance and breeding status fluctuates with rainfall in rest of range. For example, in southwestern New Mexico, few records from 1887 to 1959, mostly from late July and August. Then in 1960s singing males and some presumed female birds seen most years in early and mid June (4). “Large numbers” (variously defined) reported in southwestern New Mexico in American Birds/Field Notes regional reports for 1974, 1976, winter and spring but not summer 1977, 1981, 1990, 1991, 1992. Few reports in intervening years despite active search. During years of high numbers, local populations can be substantial; e.g., 80 singing males in Animas Valley, 160 birds in Playas Valley, New Mexico, on 9 August 1990 (98).

Difficult to identify actual changes in distribution due to confusion in older published literature about species' status in northern and western part of range. The American Ornithologists' Union Checklist (99) described western and northern limits of breeding range as southeastern Nevada, southeastern Colorado and southwestern Kansas. Phillips (5) stated that this range was in error as no records existed at that time for Utah, western Colorado, or northern and western Arizona, while only one casual record existed for Nevada. Phillips cited records of Flight Songs (see Sounds: Vocalizations), territorial behavior, enlarged testes, and even partial nest-building in Arizona during this period, but did not consider this to be evidence of breeding. Based on subsequent studies, it is now known that Flight Songs alone indicate paired status of male (7). By the mid 1980s, Cassin's Sparrow was known to be well established as a regular breeder in southeastern and central Arizona (RKB, CEB, JBD), with breeding records as far west as Prescott in some years (100, 101). Comparison of Phillips (5) with current knowledge implies change of species' status in western U.S., but current interpretation of Phillips's evidence suggests this sparrow was almost certainly breeding in the earlier period. Therefore current records may not reflect change.

Wolf (3) also specifically excluded Arizona from breeding range as he knew of few documented nests, and suggested extent of breeding range in Mexico was “not documented.” Wolf collected males with enlarged gonads in Chihuahua and San Luis Potosí, and reported singing males in Nuevo León, but suggested that the Chihuahua birds might be “early migrants,” which seems doubtful since they were collected in mid June. Since publication of Wolf's seminal work on the genus Aimophila (sensu lato), breeding has been confirmed for southeastern Arizona, as well as southwestern New Mexico, Wyoming, and Nebraska.

First Nebraska nest was found in Perkins County in mid June 1974 (89). Also reported that year from 6 other counties, but only one previous record for state (102, 89). Unreported thereafter in American Birds from Nebraska until 1988, when reported in Dundy, Hitchcock, and Chase counties (103) during a dry summer. Reported in Dundy and Box Butte counties 1989–1991, then in Keith County in 1993, about 55 km from the original 1974 site in Perkins County (54).

First Wyoming record was in June 1978 near the border with Nebraska, a 350-km range extension (89). Second record was in Platte County in 1989. Singing males reported each year from 1990–1994 from Goshen County near Nebraska border. The first nest record for Wyoming was found 31 July 1993 near Torrington (90), where probably fewer than 10 pairs nest annually, the only known nesting area in the state (53).

Fossil History

No information.

Recommended Citation

Dunning, J. B., Jr., R. K. Bowers Jr., S. J. Suter, and C. E. Bock (2018). Cassin's Sparrow (Peucaea cassinii), version 2.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.