Exotic vegetation has become a major habitat component in many ecosystems around the world, sometimes dramatically changing the vegetation community structure and composition. In the southwestern United States, riparian ecosystems are undergoing major changes in part due to the establishment and spread of the exotic Tamarix (saltcedar, tamarisk). There are concerns about the suitability of Tamarix as habitat for birds. Although Tamarix habitats tend to support fewer species and individuals than native habitats, Arizona Breeding Bird Atlas data and Birds of North America accounts show that 49 species use Tamarix as breeding habitat. Importantly, the relative use of Tamarix and its quality as habitat vary substantially by geographic location and bird species. Few studies have examined how breeding in Tamarix actually affects bird survivorship and productivity; recent research on Southwestern Willow Flycatchers has found no negative effects from breeding in Tamarix habitats. Therefore, the ecological benefits and costs of Tamarix control are difficult to predict and are likely to be species specific and site specific. Given the likelihood that high-quality native riparian vegetation will not develop at all Tamarix control sites, restoration projects that remove Tamarix but do not assure replacement by high-quality native habitat have the potential to reduce the net riparian habitat value for some local or regional bird populations. Therefore, an assessment of potential negative impacts is important in deciding if exotic control should be conducted. In addition, measurable project objectives, appropriate control and restoration techniques, and robust monitoring are all critical to effective restoration planning and execution.

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While we have learned much about the flycatcher over this 10-year study, there are still many important areas for future research. These include: whether small populations have different population dynamics than the large populations we studied; development of improved or new demographic models to help guide complex management decisions; development of spatial models that link key determinants of flycatcher habitat (e.g., groundwater, stream flow) to the characteristics of suitable habitat (as identified by our models); development of decision tools to conduct scenario planning and address management issues; the role and impact that emerging disease threats may have on flycatcher populations; and a better understanding of the migration ecology of flycatchers. Coordination with Arizona Game and Fish DepartmentThroughout this research effort, project leaders and field staff of the USGS and AGFD worked cooperatively to collect the data upon which this report and other related science products are based. AGFD and USGS had concurrent field crews working within the same study sites at Roosevelt Lake and

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