Toxostoma curvirostre is found in southeastern and central Arizona, southeastern parts of Colorado, northeastern New Mexico, through western and central Texas and south to Mexico.

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: RESIDENT: northwestern Arizona, northeastern New Mexico, southeastern Colorado, western Oklahoma, southwestern Kansas, and central Texas south to northwestern Nayarit, through Mexican Plateau to central Oaxaca and Veracruz, and central Tamaulipas (Tweit 1996, AOU 1998).

T. curvirostre is an overall brownish-gray bird that quite effectively blends in with its surroundings. The chest is mottled and the tail is dark gray. A very conspicuous characteristic of T. curvirostre is the golden-orange color of its eyes and of course the long curved bill that gives it its name. Both male and female are between 9.5"-11.5" in length; there is no sexual dimorphism evident in this species.

Length: 28 cm

Weight: 79 grams

See Kaufman and Bowers (1990) for detailed information on identification.

• Terrestrial

The curve-billed thrasher prefers dense aggregations of cholla cactus, mesquite, or palo verde. It will also choose dense urban areas as long as there are suitable nesting areas nearby.

Terrestrial Biomes: desert or dune

Comments: Inhabits arid thornscrub, chaparral, cholla (Opuntia) grasslands, and other brushy areas (Terres 1991, Tweit 1996). Typical woody vegetation of occupied Texas chaparral includes mesquite (Prosopis glandulosa), colima (Zanthoxylum fagara), acacia (Acacia rigidula), agarito (Berberis trifoliata), brasil (Condalia hookeri), and granjeno (Celtis pallida; Fischer 1980, 1981). Inhabits creosote bush (Larrea tridentata) communities, the palo verde-saguaro community, cholla grasslands, and thornscrub in Arizona; cholla grasslands in Colorado and adjacent states; and thornscrub and brushy field edges in Mexico. Also inhabits meadows and fields adjacent to pine (PINUS)-oak (Quercus) woodlands in Arizona and New Mexico (Marshall 1957, Phillips et al. 1964, Terres 1991, Tweit 1996). Inhabits cities in Arizona (Bent 1948, Phillips et al. 1964).

Nests in a wide variety of cacti, shrubs and small trees throughout its range. In south Texas, nests are located most often in yucca (Yucca treculeana), oak (QUERCUS VIRGINIA), and colima (Fischer 1980). Nests in tree cholla (Opuntia imbricata) and mesquite in Oklahoma; jumping cholla (O. FULGIDA), soaptree yucca (Y. ELATA), jujube (Ziziphus jujuba), mistletoe (Phoradendron), Lycium, mesquite, and occasionally, in woodpecker holes in saguaro and sycamore (PLANTANUS WRIGHTII) in Arizona; and in cholla cactus, nopalo cactus (O. FICUS-INDICA), acacia (A. GREGGII), prickly pear (Opuntia spp.), organ pipe cactus (Cereus thurberi), mesquite, and oak in Mexico (Clark 1904; Gilman 1909; Hensley 1959; Tweit 1996; R. Tweit, pers. comm.). Nest height ranges from 0.7-6.0 meters above the ground, but the majority are built 1-2 meters high (Anderson and Anderson 1973, Clark 1904, Gilman 1909, Hensley 1959, Tweit 1996).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Considered partly migratory; however, juvenile dispersal may be mistaken for migration (Tweit 1996).

T. curvirostre is an omnivore that uses its curved bill to probe for insects under dead leaves and other debris. While insects are its main food source, other food items include cacti seeds, prickly pear fruit, and various berries.

Comments: Forages primarily on the ground, using beak to probe soil and leaf litter and sweep leaf litter aside. Also digs into soil and moves cover objects (woody debris, cow and horse manure) to expose invertebrate prey beneath (Bent 1948, Marshall 1957, Fischer 1981). Will ascend shrubs and trees to forage on berries (Fischer 1981). Where sympatric, curve-billed thrashers forage in more open areas than long-billed (Toxostoma longirostre) or brown thrashers (T. RUFUM; Fischer 1981). Omnivorous and opportunistic feeder; diet includes a wide variety of animal and plant matter. Stomach contents vary among location and temporally in the same location (R. Tweit, pers. comm.). Nine stomachs examined by Marshall (1957) contained (in order of decreasing frequency) plant bulbs, rocks, seeds, insects, green plant material and a large grub. Fischer (1981) found 73 percent arthropod matter and 28 percent plant matter in seven stomachs collected in October, and 94 percent arthropod matter and 6 percent plant matter in three stomachs collected in March. Beetles (Coleoptera) dominated the arthropod portion of the diet, whereas fruits of hackberry (Celtis laevigata) and brasil comprised most of the plant material. Eight stomachs collected in spring and 10 collected in summer contained 44 percent:56 percent and 29 percent:71 percent Plant:animal matter, respectively (Martin et al. 1951). Plant foods include prickly pear, wheat (Triticum), corn (Zea mays), brasil, chufa (Cyperus), barley (Hordeum vulgare), nightshade (Solanum), hackberry, and bristlegrass (Setaria). In south Texas, terrestrial arthropods comprised 97 percent of the diet of nestlings; principal prey groups included orthopterans (60.4 percent), coleopterans (16.4 percent), lepidopterans (12.4 percent), and arachnids (7 percent; Fischer 1983). Probes the deep flowers of saguaros, apparently for nectar (Anderson and Anderson 1973). Will feed at feeders. Water is obtained from fleshy fruit of cacti, water holes, dripping faucets and bird baths (Bent 1948).

Population density varies with habitat disturbance. In Arizona, an average of 63 thrashers per square kilometer inhabit undisturbed to moderately disturbed palo verde-saguaro habitat; only 6.5 individuals per square kilometer inhabit disturbed palo verde-saguaro habitat dominated by exotic vegetation (Tweit and Tweit 1986). In south Texas brushland, Emlen (1972) estimated a density of 5-10 thrashers per square kilometer. Abundances for three BBS routes range from an average of 9.3-39 individuals per route (Price et al 1995).

Each pair maintains a permanent, year-round territory. Territory size ranges from 2 hectares in south Texas brushland to 2.5-4.5 hectares in palo verde-saguaro habitat in Arizona (Fischer 1980, Tweit 1996). In south Texas, six pairs renested within 30 meters of where they nested the previous year; two pairs nested within 60 and 75 meters of previous nests; and one remated female nested within 100 meters of her previous nest (Fischer 1980). In Arizona, two males nested in their respective territories annually for six years (Anderson and Anderson 1973).

Oldest, known-age wild bird lived 10 years, 9 months. The recapture of only 6 percent of 345 young banded from one month-one year earlier in Arizona suggests high juvenile mortality and/or dispersal (Tweit 1996). In south Texas, 94 percent of adults survived from one breeding season to the next (Fischer 1980). Average annual survival of adults in Arizona was 79 percent (Anderson and Anderson 1973). The sex ratio approximates unity, but quantitative data are unavailable (Tweit 1996).

Average lifespan

Status: wild: 129 months.

It builds its nest most often in cholla cactus, usually under the upper protective arms. Twigs are used to construct the nest. Two to four light blue eggs are laid; and the altricial young hatch between 12 to 15 days.

Average time to hatching: 13 days.

Average eggs per season: 3.

Phenology of breeding season is influenced by temperature and timing and amount of rainfall. Although most eggs are laid between March and May in Arizona, egg laying can begin as early as late January (Tweit 1996). The nesting season recorded during a two-year period in southern Texas ranged from 13 April through 20 July (Fischer 1980). Nesting in the Rio Grande Valley of Texas begins in March (Bent 1948). Normally two clutches are produced in south Texas, but up to three can be produced if the first two clutches fail (Fischer 1980). In Arizona, an average of 2.2 (maximum of four) clutches are laid (Anderson and Anderson 1973). Average clutch size is 3.8 eggs (range = 3-5) in south Texas; 2.8 eggs (range = 2-4) in Sonora, Mexico; and 3.2, 2.5, and 2.7 eggs for three studies in Arizona (Fischer 1980, Tweit 1996). Larger average clutch size in Texas may correlate with a more reliable food supply (R. Tweit, pers. comm.).

Incubation is initiated before all eggs are laid. Both sexes incubate the eggs an average of 14 days (range = 12-15), but females incubate for longer periods than males (Fischer 1980, Hensley 1959). Hatching success varies from 54.5 percent-71 percent across the range (Tweit 1996). Nesting success is 44 percent in south Texas, with predation accounting for 40 percent of the loss of eggs/young. Nests constructed in yucca are significantly more successful than those placed in other vegetation, and shaded nests are more successful than unshaded nests (Fischer 1980, Tweit 1996).

In Arizona, nesting success ranges from 21-44.5 percent (Anderson and Anderson 1973, Edwards and Stacy 1968 cited in Tweit 1996). Parent birds preferentially feed larger, older nestlings during food shortages resulting in brood reduction by starvation of younger nestlings (Ricklefs 1965). Both sexes feed the young (Fischer 1980, Hensley 1959). Sexually matures in one year (Tweit 1996).

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Comments: PREDATION: Suspected predators of eggs, nestlings, and fledglings include striped whipsnakes (Masticophis taeniatus), Texas patchnosed snakes (Salvadora grahamiae), western diamondback rattlesnakes (Crotalus atrox), and ants (Formicidae). Confirmed nest predators include coachwhips (Masticophis flagellum), bullsnakes (Pituophis melanoleucus), kingsnakes (Lampropeltis getula), desert spiny lizards (Sceloporus magister), roadrunners (GEOCCOCYX CALIFORNIANUS), round-tailed ground squirrels (CITELLUS TERETICAUDUS), Harris' antelope ground squirrels (AMMOSPERMOPHILUS HARRIS), and Harris' hawk (Parabuteo unicinctus; Fischer 1980, Tweit 1996). PARASITISM: Brood parasitism by cowbirds (Molothrus spp.) is rare (Tweit 1996). HABITAT: Its preferred U.S. habitats, the Texas brushlands and the Sonoran Desert in Arizona, are being lost to development and conversion to grassland monocultures (especially buffel grass, Pennisetum CITUARE; Tweit 1996).

Restoration Potential: Could probably be restored to areas of former occurrence following restoration of native vegetation.

Management Requirements: When native vegetation is maintained, residential development in the palo verde (Cercidium MICROPHYLLUM)-saguaro (Carnegia gigantea) community of Arizona at a density of two houses per hectare does not reduce thrasher density (Tweit and Tweit 1986).

Management Research Needs: Need to generate and enforce standards for compatible development to avoid further reductions in population densities.

Biological Research Needs: Taxonomic studies needed to understand subspecies relationships; preliminary mitochondrial DNA evidence suggests the thrasher may actually be more than one species. Studies of juvenile dispersal are needed to resolve questions about migration. Identification of and ecological relationship to parasites needed (Tweit 1996).

T. curvirostre may benefit humans by reducing the numbers of pest or damaging insects. As a seed eater, it may play a role in seed dispersal.

Also, T. curvirostre is an enjoyable species to observe in nature. Its antics will keep the observer amused for hours.

Stewardship Overview: Although capable of inhabiting urban and suburban environments when native vegetation is maintained, populations have declined 61.8 percent from 1966-1993 as detected by North American Breeding Bird Survey (BBS; Price et al. 1995). The decline is attributable to loss of habitat, principally as a result of development. Conversion of shrubland to grassland has also contributed to habitat loss. BBS and Christmas Bird Counts provide valuable data on population trends.

Comments: May be comprised of more than one species (Tweit 1996). Mitochondrial DNA analysis by Zink et al. (2001) show a genetic division between populations of the Sonoran and Chihuahuan deserts. Monroe and Sibley (1990) suggest that this taxon appears to constitute a superspecies with T. OCELLATUM, but this hypothesis is not supported by phylogenetic analysis of Zink et al. (1999), who state that "The relationships of T. CURVIVROSTRE and T. OCELLATUM are problematic, and the two taxa do not appear to be sister species." Placed in Sturnidae in Sibley and Ahlquist (1984).