The Curve-billed Thrasher, which forages on the ground beneath shrubs and
cacti, is about a foot in length and generally grayish brown in color. It has
robust legs, feet and bill - typical of ground-foraging birds - which
it uses to shuffle through plant litter and dig into the soil in its search for
seeds and insects. During the breeding season, the male may take a conspicuous
perch and issue a loud and melodic call for a mate. The male and female resemble
each other closely. The bird may belong to any one of several subspecies, some
of them confusingly similar, across its expansive range.
Distinctive Features
- Approx. one foot in length
- Wingspan approx. 13 inches
- Color is grayish-buff
- Throat may be whitish.
- Bill and legs black in color
- Downward curved (“decurved”) bill.
- Eyes are orange in color
- Long tail feathers
Range and Migration Habits
The Curve-billed Thrasher occupies a wide range. In the United States, the
bird occurs most commonly in the western two thirds of Texas and in the southern
halves of New Mexico and Arizona. In Mexico, it occurs from the states of Sonora
and Chihuahua southward to Oaxaca, south of Mexico City. It inhabits lower elevations
from the Sea of Cortez eastward to the Gulf of Mexico. Some populations in the
northern parts of the bird’s range may migrate over limited distances,
moving, for instance, from mountain flanks down into desert basins during the
winter and returning from the basins to the mountain flanks in the summer. Other
populations appear to remain in the same area year round.
Habitat
In the desert basins of Arizona, New Mexico and western Texas, the Curve-billed
Thrasher prefers shrub- and grasslands that have cholla cacti, a choice plant
for nesting. Along the mountain flanks, it favors thorny thickets at the edges
of Pi–on Pine and Gamble Oak woodlands. In its scrubby and prickly home,
the bird moves in quick, darting runs or flights from bush to bush.
Diet
The Curve-billed Thrasher’s diet includes:
- Seeds
- Cacti fruit & berries
- Insects
Using its decurved bill as the primary instrument for sorting, nervously and
quickly, through plant litter and for digging in the soil, the bird seeks out
cacti and other plant seeds as well as various insect prey. In season, it feeds
on cacti fruit, which offers both nutrients and moisture during the months of
drought. It may visit backyard seed feeders placed on the ground or hung from
lower branches.
Behavior/Life Cycle
A Curve-billed Thrasher, with its mate, may proclaim territory by singing
from perches at the perimeter, which can encompass several acres. A pair may
occupy the same territory throughout their lives.
They will defend their immediate nesting neighborhood and food sources vigorously
against competitors from other species as well as those from its own species.
Typically, a pair, which may form a long-lasting bond, mates in the winter,
after a courtship laced with song. Beginning in the
early spring the two birds cooperate in building a nest,
fashioning a bowl-shaped structure lined with long grass, ideally in the lower,
more shaded branches of a cholla. (By contrast, the Cactus Wren often builds
a rugby ball-shaped pouch-like nest in cholla.) The female Curve-bill Thrasher
lays her bluish green to yellowish blue eggs with reddish brown speckles early
in the morning on successive days, usually producing a total of three or four.
Both birds incubate the eggs.
Within some two weeks, the pair watch as their offspring begin to hatch, naked
and helpless, on successive days, in the order in which the mother bird laid
the eggs. Over the next two to three weeks, the pair struggles to tend to their
nestlings. They answer their nestlings’ incessant cries for food, which
may include fruit, pollen, nectar and insects taken from nearby cacti. They fret
over their nestlings’ squirms as limbs develop and feathers appear.
They oversee their nestlings’ emergence from the nest and their first
clumsy attempts at flight.
For the next several weeks, they nurture the fledglings, still answering their
cries for food but teaching them the art of foraging and reinforcing their call
to independence. About six weeks after the female produced her first clutch,
her offspring will take their leave, looking forward, with good luck, to a lifespan
of several years. Meanwhile, the female rushes to produce a second clutch, and
maybe even a third, before the season ends.
Life’s Hazards & Predators
Typical of nature, a young Curve-billed Thrasher faces an obstacle course
of life-threatening hazards as it grows and matures. In hard times, it may simply
starve, its parents unable to provide sufficient food. It may fall to predation
by a snake, a raptor, a roadrunner, a rodent, or, occasionally, ants. It may
even impale itself, inadvertently and fatally, on a cactus thorn.
Interesting Facts
- A pair of Curve-billed Thrashers may build successive nests
in the same cholla, sometimes superimposed over Cactus Wren nests.
- Once they leave the nest, young Curve-billed Thrashers may “play,” bouncing,
hopping and circling, using their beaks to tug at grass and twigs.
- When courting a potential mate, the Curve-billed
Thrasher produces a surprisingly lyrical song, with great variation in its phrases,
according to the famed naturalist Roger Tory Peterson in his Western
Birds.
