Saltcedar and Southwestern Willow Flycatchers: Lessons From Long-term Studies in Central Arizona

Abstract

The endangered Southwestern Willow Flycatcher (Empidonax traillii extimus: SWWF) is a riparian-obligate bird that breeds only in dense, typically wet riparian vegetation. Since the mid-1990s, biologists have discovered a substantial number of flycatchers breeding in habitat dominated by exotic saltcedar (Tamarix ramossisima) in sites across Arizona, New Mexico, Nevada, and Utah. Today, approximately 25 percent of SWWF breeding sites, supporting one-third of the roughly 1,300 known flycatcher territories, are in saltcedar-dominated sites. A widely held belief is that this saltcedar habitat must be sub-optimal for the SWWF. Therefore, studies were conducted to determine if there are negative effects to SWWFs breeding in saltcedar. Although diet of flycatchers in native and saltcedar habitats differs, dietary differences are not proof that food resources are limiting or insufficient in one habitat compared to the other. Long-term studies of flycatcher physiology, immunology, site fidelity, productivity, and survivorship found no evidence that nesting in saltcedar-dominated habitat is detrimental to Southwestern Willow Flycatchers at breeding sites in central Arizona. It is likely that saltcedar habitats vary with respect to suitability for breeding flycatchers across their range, just as do native habitats; therefore, results from a single study or site may not be applicable across the ranges of the SWWF or saltcedar. Ultimately, multiple long-term studies over a large geographic area must be compared to determine the relative suitability of native and saltcedar habitats at the landscape scale.

Parent Publication

• Monitoring Science and Technology Symposium: Unifying Knowledge for Sustainability in the Western Hemisphere

Citation

Sogge, M. K.; Paxton, E. H.; Tudor, April A. 2006. Saltcedar and Southwestern Willow Flycatchers: Lessons From Long-term Studies in Central Arizona. In: Aguirre-Bravo, C.; Pellicane, Patrick J.; Burns, Denver P.; and Draggan, Sidney, Eds. 2006. Monitoring Science and Technology Symposium: Unifying Knowledge for Sustainability in the Western Hemisphere Proceedings RMRS-P-42CD. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 238-241