Distribution, abundance, and habitat characteristics of Southwestern Willow Flycatchers (Empidonax traillii extimus) in Arizona, 1993-2000

To determine the distribution and abundance of Southwestern Willow Flycatchers (Empidonax traillii extimus) in Arizona, personnel from many federal, state, tribal, and private entities conducted presence/absence surveys yearly, from 1993-2000. To aid recovery efforts for this endangered species, we synthesized the results of these surveys to provide a comprehensive estimate of Southwestern Willow Flycatcher distribution and abundance in Arizona. Surveys were conducted along 1279 km of riparian habitat in 17 drainages. Surveyors documented flycatchers within 16 geographical locations below 1500 m and one location above 2200 m in elevation. Below 1500 m, flycatchers occupied riparian forests dominated by mixtures of willow (Salix sp.) and tamarisk (Tamarix sp.) with median height 8.5 m (range 3-24 m). Above 2200 m, breeding sites consisted of Geyer willow (Salix geyeriana) patches with median height 4 m (range 3.5-4 m). Estimated number of territories increased from 32 in 1993 to 328 in 2000; this increase was largely the result of increased survey effort. Two locations (Roosevelt Lake and Gila/San Pedro River confluence) contained 71% of the known population. Historically, Southwestern Willow Flycatchers occurred along most major river drainages in Arizona. We compared current (1993-2000) distribution with historical records and found that flycatchers recently occurred in nine historic locations and were absent at four. Southwestern Willow Flycatchers in Arizona constitute one third of the range-wide population and this synthesis identifies extant populations where protection is needed, as well as future research needs.