New Study Details Endangered Southwestern Willow Flycatcher Habitat and New Threats

A new report by the U.S. Geological Survey shows, for the first time ever, detailed habitat information on the entire range of a federally listed endangered bird allowing officials to take a scientific approach to helping protect the species. The Southwestern Willow Flycatcher – a small songbird currently listed as endangered under the Endangered Species Act – breeds in lush, dense vegetation along rivers and streams in the southwestern U.S. from May through September. In 2013, the U.S. Fish and Wildlife Service designated 1,975 stream kilometers as critical flycatcher habitat, located in six states and 38 counties. “The satellite model provides us with new capabilities to locate and monitor potential flycatcher habitat within individual watersheds and across its entire range” said James Hatten, Research Biogeographer with the USGS and the report’s author. “The satellite model also revealed how the quantity of flycatcher habitat is affected annually by drought conditions, with habitat declining in California from 2013 to 2015, while increasing in New Mexico and Texas.” A secondary objective of the project was to identify how and where the recently introduced tamarisk leaf beetle is affecting flycatcher habitat in the southwestern United States. In 2001, tamarisk leaf beetles were released by the U.S. Department of Agriculture Animal and Plant Health Inspection Service at 10 sites in six states (California, Nevada, Utah, Colorado, Wyoming and Texas) to control invasive tamarisk, an introduced plant that occurs adjacent to rivers and creeks. Beetles have now spread into the upper Colorado River Basin in southern Utah and Nevada, the main stem lower Colorado River in Arizona, and the Rio Grande in New Mexico. Beetles pose a threat to flycatchers by defoliating tamarisk during nesting, exposing their young to increased temperatures and predation. The model found that beetles decreased flycatcher habitat 94 percent from 2010 to 2015 along the lower Virgin River, with only 6 percent remaining. The model also predicts that the beetle will destroy 36 percent of flycatcher habitat along the lower Colorado River and 55 percent along the upper Gila River in the next decade...more