Curve-billed Thrasher

The curve-billed thrasher is immediately recognized as a thrasher by its long tail and short wings. It is also recognized for its sickle-shaped bill, almost as long as its head width and brownish black in color. The body is compact with a large head, short wings and long tail. However, the tail is short relative to other thrasher species. The chest is grayish brown with circular brown-gray spots. The eyes are generally orange, shading to golden in adulthood. Juveniles are lacking in pale tips, rectrices, abdominal feathers are unkempt and upper parts and chest are washed rufously. Variations are markedly different with each subspecies. The eastern subspecies has more distinct spots on its chest, more white along the tips and rectrices and obvious wing bars. T.c. palmeri has less spotting on chest and tips and less obvious wing bars. Other examples include T.c. curvirostre possessing longer wings and a tail than T.c. oberholseri; T.c. insularum is paler with more grey than T.c. palmeri and has more visible spotting on its breast. One study published in 2003 suggested that curve-billed speciation was due to climate, which could be explained by molt and feather wear. …

The curve-billed thrasher is commonly found throughout the southwestern United States from Arizona's Sonoran Desert across New Mexico to west Texas, southeastern Colorado and southwestern Kansas as well as most of Mexico from the Sonoran-Chihuahuan Deserts and south through the Mexican Plateau into Central Tamaulipas, inland to Oaxaca, and on the coast of Sonora to Nayarit. Vagrants have been found in bordering states of its range, as far north as North Dakota, Alberta and Manitoba and as far east as Florida. Palmeri types have been spotted in Florida, while curvirostre have been found in Iowa on several occasions. Other than previously noted exceptions, the curve-billed is essentially non-vagrant. In comparison with other desert thrashers, the curve-billed is not as particular with habitats and can be found from sea-level up to 3,000 m (9,800 ft). It generally resides where cholla and saguaro cacti, ocotillo, mesquites, palo verde, and creosote bushes are prevalent. It can also be located along woodland edges, piñon, dry desert bushland and areas within its region where cacti are present. If there is an adequate amount of desert vegetation near human habitation, along with feeders, the curve-billed can adapt within these environments.

The curve-billed thrasher can generally be found running rapidly from cover to cover or flying near ground level from bush to bush. However, this bird is not shy about being in the open. It is generally a forager on ground level but can be very aggressive in routing out potential competitors for food at feeders, such as the Inca dove and round-tailed ground squirrel.

Mating. One recorded case of courtship behavior involving curve-billed thrashers describes two males attacking each other vigorously and resorting to purring and hissings sounds when neither bird appeared to relent. The two males then puffed up their chests and strutted up and down in front of the female. They continued to alternate between purr and hiss and fighting one another until one triumphed. The victor flew towards the female and both chirped melodically before copulation.

Breeding. The curve-billed breeding season begins in February and reaches an apex between March and May; however, new fledglings have been recorded as late as August. Dates vary within its range due to temperature and rainfall. Nests are generally built at conspicuous locations, the cholla being favored. Other potential nesting sites range from mesquite, prickly pear or yucca to the occasional oak and pine trees. The nest is generally a deep cup but can be flat with a depression for the eggs. …