The Southwestern Willow Flycatcher occurs in dense riparian habitats along streams rivers, and other wetlands. At low elevations, the flycatcher breeds in dense, patchy habitats composed of mid-sized to tall trees and shrubs. At higher elevations, it occurs in dense stands of low to moderate height riparian shrubs. Vegetation density within 4 m (13 ft) is especially important. Preferred habitats are almost always associated with standing or slow-flowing water. The destruction of riparian habitats has caused a severe decline in the populations of the southwestern willow flycatcher. Currently, this sub-species exists only in fragmented and scattered locations throughout its range. Historically, the breeding range reached from southern California, southern Nevada, southern Utah, Arizona, New Mexico, western Texas, southwestern Colorado, and northwestern Mexico. The flycatcher is a migratory bird that winters in Mexico, Central America, and northern South America. Currently, the breeding range for the flycatcher is similar to the historic range, though much of the riparian habitat in the southwest has been degraded by agricultural practices, invasion of non-native vegetation and urban development. The Southwestern Willow Flycatcher is an insectivore, taking insects from the air, or picking them from the foliage. The Southwestern Willow Flycatcher is present on breeding grounds by mid-May. By late May, nests are built, usually in a branched tree fork near the water. Typically, three eggs are laid and then incubated for 12–13 days.