The Colima Warbler is a small, secretive warbler that breeds primarily in the mountains of western Mexico. In the United States, it occurs regularly only in the Chisos Mountains of Texas, making it one of the most geographically restricted breeding birds in the country. It inhabits steep oak, pine-oak, and montane woodland canyons, where it forages for insects among leaf litter, shrubs, and low vegetation. Colima Warblers winter in southwestern Mexico and return to Texas each spring to breed. Because of its limited U.S. range and remote habitat, it is considered a sought-after species by birders visiting Big Bend National Park.
Habitat
The Colima Warbler inhabits steep montane canyons, oak woodlands, pine-oak forests, and brushy mountain slopes. In the United States, it is closely associated with the rugged canyon systems of the Chisos Mountains, where dense leaf litter, shrubs, and woodland understory provide ideal foraging and nesting habitat. Throughout its broader range in Mexico, it occupies similar high-elevation woodland and canyon environments.
Diet
The Colima Warbler feeds primarily on insects and other small arthropods. Its diet includes caterpillars, beetles, ants, spiders, flies, and various larvae that it gleans from leaf litter, low vegetation, shrubs, and tree foliage. It often forages close to the ground, searching through dead leaves and understory vegetation for prey.
Behavior
The Colima Warbler is a secretive bird that spends much of its time foraging low in shrubs, woodland understory, and leaf litter on steep canyon slopes. Unlike many warblers that feed high in the canopy, it frequently works close to the ground, hopping through dense vegetation in search of insects and spiders. Males sing persistently from exposed perches during the breeding season but can be surprisingly difficult to see despite their vocal activity. The species is generally solitary or found in pairs during the breeding season and becomes even more inconspicuous on its wintering grounds in Mexico.
Nesting
The Colima Warbler builds a well-concealed cup nest on or very near the ground, typically tucked beneath grasses, shrubs, rocks, or overhanging vegetation on steep canyon slopes. The nest is constructed from grasses, leaves, bark strips, rootlets, and other plant materials and is often difficult to locate because of its excellent camouflage. Typical clutches contain 3–4 eggs, and the female performs most of the incubation while both parents help feed the nestlings after hatching.
Song
The Colima Warbler sings a distinctive series of clear, ringing whistles that are often rendered as wee-chi-chi-chi. The song is loud, simple, and repetitive, carrying well through mountain canyons and often revealing the bird's presence long before it is seen. Calls include sharp chip notes and short contact calls given while foraging in dense vegetation.
Migration
The Colima Warbler is a migrant that breeds in the mountains of western Mexico and, in the United States, only in the Chisos Mountains. After breeding, it migrates south to winter primarily in southwestern Mexico, where it occupies montane woodlands and forested slopes. Spring migrants return to their breeding grounds from April into May, and most birds depart again by late summer or early fall. Unlike many North American warblers, the entire annual cycle of the species is closely tied to mountainous habitats.
Similar Species
Virginia's Warbler , Nashville Warbler. The Colima Warbler can be confused with both the Virginia's Warbler and the Nashville Warbler, but several features help separate them. Colima Warblers are relatively plain gray overall with a faint buff wash on the undertail coverts and a noticeably long tail that is often pumped or flicked downward. They lack the bright yellow underparts and contrasting facial patterns seen in many other warblers and are usually found low in dense vegetation on steep mountain slopes.
The Virginia's Warbler is smaller and shows a yellow patch on the breast and undertail area. Adults often display a small rusty crown patch, especially in males, and generally have a shorter-tailed appearance than Colima Warblers.
The Nashville Warbler is brighter overall, with yellow underparts, a yellow throat, and a more obvious white eye ring. Nashville Warblers also tend to forage higher in shrubs and trees and appear more colorful than the relatively subdued Colima Warbler.
Range is often the most useful clue. In the United States, Colima Warbler breeds only in the Chisos Mountains, whereas Virginia's and Nashville Warblers are much more widespread during migration and breeding. Outside the Chisos Mountains, a bird resembling a Colima Warbler is far more likely to be one of these other species.
Conservation Status
The Colima Warbler has been listed as a species of "least concern" by the IUCN . Populations are small and they breed in a relatively small geographic area, but the habitat they prefer is generally inaccessible and on land that's of little economic value to human beings. Therefore, while not a common species, extirpation due to habitat destruction or human activity may be unlikely.
Photo Information
Photo by National Park Service
Interactive eBird Map
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