Distribution and characteristics of Southwestern Willow Flycatcher breeding sites and territories: 1993 - 2001

Abstract

Effective conservation and management of an endangered species requires knowledge of its abundance, distribution, and breeding site characteristics. Using published literature, unpublished reports, and personal communications, we synthesized information on all known Southwestern Willow Flycatcher (Empidonax traillii extimus) breeding sites from 1993 through 2001. Due to extensive survey efforts throughout the Southwest, the number of known flycatcher territories has increased from 111 (in 1993) to 986 (in 2001); the number of known breeding sites similarly increased from 30 to 221. Most territories are found within small breeding sites (those sites with five or fewer territories); only two sites have 50 or more territories. Sixty-five sites have been extirpated since 1993; 61 of these had five or fewer territories. The states of California, Arizona, and New Mexico account for 89% of known territories; Nevada, Colorado, and Utah collectively have 11%. Approximately half of territories are in habitats comprised of .90% native plants; the other half have a .10% exotic tree and/or shrub component. Approximately 90% of territories are in habitats where willow (Salix spp.), saltcedar (Tamarix ramosissima), or boxelder (Acer negundo) are the dominant tree species; boxelder use occurs only in the Cliff-Gila Valley, New Mexico. Slightly less than half of all sites are on federally-controlled lands; 26% are on private lands. Privately owned sites account for 37% of known territories, and one-third (35%) of these are found in the Cliff-Gila Valley. No data are available on the current status of the Southwestern Willow Flycatcher in Texas or northern Mexico.