The Rufous-crowned Sparrow of the southwestern United States has been divided into two population groups: smaller,, more reddish birds from California and larger, browner individuals from Texas, New Mexico, Colorado, Utah and Arizona. Behavior of the species has not been studied extensively enough to determine if the two groups differ in other ways (Pyle 1997, Collins 1999).
DISTRIBUTION. During the 1987-1992 field work for the TBBA project, volunteers found Rufous-crowned Sparrows breeding west of the 97th meridian in the Edwards Plateau, Trans-Pecos, High Plains and Rolling Plains regions of the state, with a few records from the South Texas Brush Country and the lower Rio Grande valley. As Lockwood and Freeman (2004) indicate the species is a year-round resident in its breeding range and rare outside these areas in winter. Thus all records probably represent breeding sites.
Outside Texas, the Rufous-crowned Sparrow is a year-round resident of the California coast range and the Sierra Nevada foothills south from northern California to northern Baja California. Other individuals reside in eastern California, southern Utah, southeast Colorado, Arizona, New Mexico and the highlands of Mexico south to the Isthmus of Tehuantepec (Collins 1999).
SEASONAL OCCURRENCE. The Rufous-crowned Sparrow is a permanent resident of Texas; its breeding season extends from mid-March to mid-August with eggs found from April 4 to July 25 (Oberholser 1974). TBBA fieldworkers found confirmed breeding evidence from April 3 to August 9 with fledged young present as early as April and nest building as late as July 8. Harrison (1979) reported the breeding season in any year is correlated with the timing and extent of rainfall.
BREEDING HABITAT. Rufous-crowned Sparrows breed from 150 to 2400 m (500 -8,000 ft) elevation on rocky slops or mesas. The nest is placed on the ground under a clump of grass, under a bush or even in a bush (less than 0.7 m [2 ft] off the ground). Ground nests are often in a hollow, deep enough that the rim of the nest is level with the soil surface. The nest is variable, generally well-constructed, sometimes bulky, a somewhat deep cup built of coarse grasses, plant stalks, thin twigs and strips of bark. the nest is lined with finer bark strips, fine grasses, plant fibers and animal hair.
The female lays 4 (range 2-5) white to bluish white, unmarked eggs, which she incubates for 11-13 days. The length of the nestling period is unknown. This species is a rare host for cowbird parasitism, probably because cowbirds are rare in the habitat occupied by Rufous-crowned Sparrow. Two broods per season are possible (Oberholser 1974, Harrison 1979, Collins 1999).
STATUS. Lockwood and Freeman (2004) report the Rufous-crowned Sparrow as common to uncommon and local in the western two-thirds of Texas. The TBBA map for this species shows a similar range to that on the map in Oberholser (1974), suggesting little or no change in range.
Breeding Bird Survey (BBS) data indicate the highest density of Rufous-crowned Sparrows in Texas is found in and around Big Bend National Park, east through the Edwards Plateau and northeast from there into the Rolling Plains, In this area BBS routes averaged 3-10 sparrows per 40 km (25 mi) route per year. Much of the rest of the Trans-Pecos region had an average of 1-3 birds (Sauer et al 2004). Analysis of individual routes by Price et al (1995) found the Indian Mountain route in Edwards County had the second-highest 5-year route average in the United States (18.6 sparrows per year).
Data from the 51 routes in Texas on which Rufous-crowned Sparrow was detected produced a 95% confidence interval of -5.9 to 1.4% (19 times in 20 the actual trend value will fall between these 2 figures) population change per year for the period 1966-2003. The 116 routes across the United States range of this species gave a 95% confidence interval of -3.0 to 1.6% change per year. The interval for Texas is disturbing especially since Texas is a very significant portion of Rufous-crowned Sparrow’s range in the United States. (Sauer et al. 2004). If we assume an average annual decline of 2.2% (the median of the 95% confidence interval), the 2003 Texas population of Rufous-crowned Sparrows is only 46% of the 1966 population. Text by Robert C. Tweit (2004)
Collins, P. W. 1999. Rufous-crowned Sparrow (Aimophila ruficeps). In The birds of North America, No. 472 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
Harrison, H. H. 1979. A field guide to western birds’ nests. Houghton Mifflin, Boston, MA.
Lockwood, M. W. and B. Freeman. 2004. The TOS handbook of Texas birds. Texas A&M University Press, College Station.
Oberholser, H. C. 1974. The bird life of Texas. University of Texas Press, Austin.
Price, J., S. Droege, and A. Price. 1995. The summer atlas of North American birds. Academic Press, New York.
Pyle, P. 1997. Identification guide to North American birds, part 1. Slate Creek Press, Bolinas, CA.
Sauer, J. R., J. E. Hines, and J. Fallon. 2004. The North American Breeding Bird Survey, results and analysis 1966-2003. Version 2004.1. USGS Patuxent Wildlife Research Center, Laurel MD (Web site, http://www.mbr-pwrc.usgs.gov/bbs).