Lucy's Warbler

Lucy's Warbler is among the smallest of all North American warblers, a delicate, pale gray bird adapted to hot, arid desert riparian habitat. Its plumage is plain pale gray above and whitish below, brightened only by a rich chestnut patch on the rump, which is often the most visible field mark, and a smaller chestnut crown patch that is frequently concealed.

Unusually for a warbler, Lucy's Warbler nests in cavities, one of only two North American warblers to do so (the other being Prothonotary Warbler), using natural tree hollows and old woodpecker holes in desert trees such as mesquite and cottonwood.

Key field marks

• Very small size, among the smallest North American warblers
• Plain pale gray upperparts, whitish underparts
• Chestnut patch on the rump, often the most visible field mark, especially in flight
• Smaller, often-concealed chestnut crown patch
• White eyering

Similar species

Virginia's Warbler is larger, shows yellow on the breast and undertail coverts, and lacks the chestnut rump patch. No other regularly occurring warbler in its desert range combines such small size, plain gray plumage, and a chestnut rump.

Lucy's Warblers breed in desert riparian woodland of the southwestern United States and northern Mexico, with a strong association with mesquite bosques as well as willow and cottonwood groves along desert washes and rivers.

They winter along the Pacific coast of western Mexico, in similarly warm, dry habitats.

Behavior and voice

Lucy's Warblers forage actively in the foliage of mesquite and other desert trees and shrubs, gleaning insects and spiders, and often stay well hidden within the dense canopy of their riparian habitat.

The song is a rapid, descending warble, often rendered as "chiff-chiff-chiff-chiff, che-che-che-che."

Nesting

Unusually for a warbler, Lucy's Warbler nests in cavities, using natural hollows, old woodpecker holes, or crevices in mesquite, cottonwood, or willow trees, and will also use nest boxes. Clutches typically contain 3-5 eggs.