Technical Report

Habitat Relationships Along the Middle Rio Grande in New Mexico for the Endangered Southwestern Willow Flycatcher

URL: https://webapps.usgs.gov/mrgescp/documents/Tetra%20Tech%2C%20Inc._2015_Habitat%20Relationships%20along%20the%20MRG%20in%20NM%20for%20the%20Endangered%20SWFL.pdf

Date: 2015/01/01

Author(s): Tetra Tech, Inc.

Publication: Prepared for U.S. Army Corps of Engineers. Prepared by Tetra Tech, Inc., 103 p.

Abstract:

The Southwestern Willow Flycatcher (flycatcher; Empidonax traillii extimus) is listed as Endangered by the U.S. Fish and Wildlife Service under the authority of the Endangered Species Act (ESA). It is also listed as Endangered by the states of New Mexico, Colorado, California, Texas, and Utah and a species of concern in Arizona and a Critically Imperiled species in Nevada. It is viewed by many as an important indicator of riparian ecosystem health.

The following report, completed by Tetra Tech under a delivery order from the U.S. Army Corps of Engineers, Albuquerque District, presents the results from an assessment focusing on issues and key habitat relationships for the flycatcher along the Middle Rio Grande (MRG) in New Mexico. It includes an analysis of existing flycatcher habitat along the MRG in terms of plant species composition and structure, patch size, location of existing breeding territories, potential for negative impacts due to groundwater change, fire, tamarisk (or saltcedar; Tamarix spp.) biocontrol by Tamarisk Leaf Beetle (TLB; Diorhabda spp.) defoliation and movement, other stressors, and connectivity and distance of habitat to surface water. Life history and autecological attributes are summarized, including food habits, feeding habitat, breeding chronology, nesting habitat, relationships of nest sites to surface water, and projections of overbanking producing floodplain inundation in relation to nest sites. Summaries of ESA regulatory requirements for the species’ listing, Recovery Plan, Critical Habitat Designation, and historical provisions of the 2003Biological Opinion for water operations along the MRG are also provided.