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. . SWWF return to wintering grounds in August and September (Brown 1991b), but neither migration routes nor wintering areas are well known. Birds call and perhaps defend foraging territories in Central America during winter, and winter movement may be tied to water availability (Gorski 1969). Threats to SWWF on the wintering grounds are poorly documented, but habitat losses in Latin America may be a major factor in the decline of this species. Impacts of BHBF BHBF's during the breeding season are unlikely to directly affect the SWWF population because SWWF nest several meters up in tamarisk trees that stand at or above the 45,000 cfs stage. In upper Grand Canyon, SWWF generally nest in saltcedar trees and nest trees typically lie above the 45,000 cfs stage. The saltcedar stands in which SWWF nest are unlikely to sustain direct damage from BHBF(s): Stevens and Waring (1988) demonstrated that saltcedar is exceptionally tolerant of flooding in the Grand Canyon, persisting through many weeks of inundation. The saltcedar trees in which the SWWF presently nest survived the >92,600 cfs flows of 1983 as well as the 1996 BHBF (Stevens et al. 1996), and are therefore unlikely to be scoured by one or more brief, 45,000 cfs BHBF's in 1998. The wetlands and low-lying areas near SWWF nesting habitats and in which they occasionally forage, are likely to continue to be affected by BHBF's. Impacts to associated wetlands ranged from 1 % to >72% from the 1996 BHBF, and impacts on those sites persisted through the 1996 growing season (Stevens et al. 1996). Although those habitats were strongly affected by the 1996 flood, actual impacts on SWWF food resources remain undocumented. It is unlikely that the 1996 BHBF affected SWWF foraging, but impacts are impossible to document with so few birds to study. SWWF forage on adult, terrestrial (non- aquatic) flying invertebrates, populations which are unlikely to be affected by a brief BHBF, and which are likely to recover promptly after the event. Stevens (1985) reported that riparian invertebrate populations increased rapidly following a flow comparable to a BHBF in 1980 (U.S. Bureau of Reclamation 1990). The habitat and population in lower Grand Canyon is influenced by Lower Colorado River basin management of Lake Mead, and present data indicate no impacts of a BHBF on SWWF habitat there. llnE;OhC;ilu~ibO; BH61F(s) in 1998 may continue to affect a non-essential component of '1l1eforagirig habitat of SWWF, but are unlikely to adversely affect the SWWF population in upper Grand Canyon. 1998 GCD Beach/Habitat Building Flow 22 Biological Assessment