POSTBREEDING MOVEMENTS OF AMERICAN AVOCETS AND IMPLICATIONS FOR WETLAND CONNECTIVITY IN THE WESTERN GREAT BASIN

Abstract

Wetlands in the western Great Basin of the United States are patchily distrib- uted and undergo extensive seasonal and annual variation in water levels. The American Avocet (Recurvirostra americana) is one of many shorebird species that use these wetlands as breeding and migratory stopover sites andmust adjust to variable conditions.We used radio telemetry to determine postbreeding, premigratory movement patterns of avocets through- out the region. In 1996 and 1997, 185 breeding adults were captured and fitted with radio transmitters at five breeding areas in Oregon, California, and Nevada. Regular aerial and ground surveys were conducted at the five main study areas from June through September, or until all avocets had left a site. Other wetlands in the western Great Basin also were sur- veyed by aircraft for the presence of radio-marked birds. Fifty-six percent of radio-marked avocets were still detected in the region at least eight weeks after capture. Each of these individuals was detected at an average of 2.1 lakes (range 0 to 6), with 74% found at more than one lake system. Forty radio-marked individuals moved at least 200 km between wet- lands prior to migration, most of which dispersed northward.Male and female patterns did not differ significantly. Overall, movements may be associated with a prebasic molt, ex- ploitation of a superabundant food source in northern lakes, and reconnaissance for future breeding efforts or staging sites. These results also demonstrate wide-ranging patterns of dispersal in this species and suggest a need for the consideration of large-scale habitat con- nectivity issues in establishing conservation strategies for shorebirds in the western Great Basin.