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Biologists survey southwestern willow flycatcher

Although migrant southwestern willow flycatchers are detected most years, in 2007 biologists detected the first resident southwestern willow flycatcher. The following year, an apparently unmated male defended a breeding territory for more than 30 days. In 2011, surveys showed the second highest number of detections at 16, and although most were migrants, again biologists identified an individual resident southwestern willow flycatcher.

A subspecies of the willow flycatcher, the southwestern willow flycatcher is listed as an endangered species. The small songbird breeds in dense vegetation at a limited number of sites throughout the southwest and has gray-brown to dull olive feathers and white wing-bars.

Southwestern willow flycatcher
Southwestern willow flycatcher

Permitted biologists have conducted surveys annually since 1998 to determine if the southwestern willow flycatcher is breeding at the Las Vegas Wash. The surveys involve determining either a presence or absence of the species and evaluating the condition of potentially suitable nesting habitat. The purpose of the survey is to ensure that the Wash stabilization program does not adversely affect the species.

The occurrence of resident southwestern willow flycatcher detections may be tied to changes in potentially suitable nesting habitat quality on the Wash, which has changed dramatically since surveys began. Native habitats were nearly nonexistent in 1998, and the tamarisk-dominated habitats were of marginal quality. Since that time, fires and clearing for weir construction further decreased tamarisk habitats. Meanwhile, the construction of erosion control structures and native riparian revegetation have substantially increased the extent and quality of potentially suitable native-dominated habitat. The 2008 southwestern willow flycatcher established its breeding territory in a revegetation site that was planted in 2002 with willows and cottonwoods by community volunteers, and the 2011 detection occurred in willow-dominated islands formed in a weir impoundment.

Although nesting of southwestern willow flycatchers on the Wash has not been confirmed to date, the increase in detections in recent years and the loss of tamarisk habitats in the region provide evidence that they may in the future. The Wash also has shown importance as a migration stopover habitat. Thus, as the stabilization and enhancement program continues on the Wash, permitted biologists will continue to conduct annual breeding surveys for the federally endangered bird. A survey for tamarisk-eating insects also has been initiated along the channel to keep an eye out for the arrival of the leaf beetle and determine any impacts on the remaining tamarisk habitats on the Wash.

Las Vegas Wash Project Coordination Team • 100 City Parkway, Suite 700 • Las Vegas, NV 89106 • (702) 822-3300