The curve-billed thrasher (Toxostoma curvirostre) and Bendire’s thrasher (Toxostoma bendirei) are two similar-looking bird species found in the southwestern United States and Mexico. While they occupy overlapping ranges and have similar behaviors, there are several key differences between these two thrasher species.
Taxonomy and Identification
Both the curve-billed thrasher and Bendire’s thrasher belong to the genus Toxostoma, commonly known as thrashers due to their habit of “thrashing” through leaf litter while foraging. However, they are separate species within this genus.
Curve-billed thrashers are medium-sized songbirds, measuring around 11.5 inches in length with a wingspan of 13 inches. Adults have grayish-brown upperparts and paler underparts with heavy spotting on the breast. As their name suggests, curve-billed thrashers have a long, downward-curving bill that is black on top and yellowish on the bottom. Their tails are long and rounded.
Bendire’s thrashers are slightly smaller, measuring around 10.5 inches in length with a wingspan of 12 inches. They share the same mostly brown plumage as curve-billed thrashers, but can be distinguished by their straighter, slimmer bill which lacks the obvious curve. Bendire’s thrashers also have more reddish-brown coloration on their heads and upper breast.
Range and Habitat
Curve-billed thrashers are found across the desert regions of the southwestern U.S. and northern Mexico. Their breeding range includes southeastern California, southern Nevada, southern Utah, most of Arizona, New Mexico and western Texas. Parts of northern Mexico are also included in their range.
Bendire’s thrashers occupy a smaller, more restricted range centered on southern Arizona and extending into adjacent areas of California, Nevada, Utah, New Mexico and Mexico. There is limited overlap with curve-billed thrashers along the Arizona-New Mexico border region.
Both thrashers inhabit hot, arid environments including desert scrub, chaparral, and open woodlands. Curve-billed thrashers are more adaptable and can thrive in suburban areas, while Bendire’s thrashers are more sensitive to habitat disturbance.
Behavior and Diet
Curve-billed and Bendire’s thrashers exhibit similar behaviors and lifestyles. They are ground-dwelling birds that spend much of their time on foot, walking along open ground while they forage. Both species have long legs suited for this purpose.
A notable behavior of thrashers is their technique of grasping food items with their bill and then rapidly hitting or “thrashing” them against the ground. This helps to smash hard-shelled insects or break open seeds. Their bills are specially adapted for this feeding method.
Thrashers are omnivorous, consuming a varied diet of insects, spiders, small vertebrates like lizards, seeds and berries. Curve-billed thrashers are more willing to visit backyard feeders for suet or seed.
Breeding and Nesting
The breeding seasons of curve-billed and Bendire’s thrashers overlap in spring, usually from March to June. However they show some differences in nest site selection and breeding behaviors.
Curve-billed thrashers often nest in cholla and prickly pear cacti, lining a nest platform built deep inside the cactus with grass and feathers. Pairs are monogamous and may nest together for multiple years.
Bendire’s thrashers favor large thorny shrubs like catclaw acacia for nest sites. Nests are well-concealed and decorated with shed snakeskin lining. Bendire’s thrashers are more secretive during breeding and may be polygamous.
For both species, females lay 3-4 eggs which hatch after 14 days. Both parents share incubation duties. Nestlings fledge in about 14-17 days but remain dependent on parents for several more weeks.
Vocalizations
Curve-billed and Bendire’s thrashers produce a wide repertoire of vocalizations used for communication. Both species have rich, melodious song but with distinctive differences allowing birders to identify them by sound.
Curve-billed thrashers sing a series ofascending and descending phrases that carry well. Their common call is a harsh, squeaky “wheep” and they make a rattling chatter when alarmed.
Bendire’s thrashers have a more hurried jumbled song in a lower pitch. Their common call sounds like “preet” and they make buzzy “zeee” alarm calls. Bendire’s may also drum bills in display.
Status and Conservation
Both the curve-billed and Bendire’s thrashers are currently listed as species of Least Concern on the IUCN Red List. However, Bendire’s thrasher numbers are decreasing and its limited range makes it vulnerable to habitat loss.Ongoing conservation efforts for Southwestern desert ecosystems will benefit both species.
Comparison Table
Attribute | Curve-billed Thrasher | Bendire’s Thrasher |
---|---|---|
Range | Southwestern U.S., northern Mexico | Central and southeast Arizona into southwest New Mexico and Mexico |
Size | 11.5 inches long | 10.5 inches long |
Bill shape | Long, curved black and yellow bill | Straight, slim all-black bill |
Plumage | Gray-brown upperparts, spotted underparts | Reddish-brown tones on head and breast |
Habitat | Desert scrub, chaparral, open woodlands | Arid desert scrub habitats |
Nest site | Cholla or prickly pear cactus | Thorny shrubs |
Diet | Insects, lizards, seeds, berries | Insects, lizards, seeds, berries |
Song | Melodic ascending and descending phrases | Rapid jumbled phrases in lower pitch |
Conclusion
In summary, while the curve-billed and Bendire’s thrashers occupy overlapping ranges and exhibit similar ecological roles, they can be differentiated by subtle variations in size, plumage, vocalizations, habitat preferences, and specific nesting behaviors. Being able to distinguish these desert bird species aids in effective monitoring and conservation efforts for the fragile ecosystems they inhabit.