Migration and Winter Ranges of Ferruginous Hawks From Washington: 2001 Progress Report

From 1999 01 we studied the migration and winter ranges of ferruginous hawks (Buteo regalis) that breed in Washington state. We attached satellite PTT’s (platform transmitter terminals) to 12 adult and 6 nestlings to monitor their long-range movements. Preliminary results from 7,120 locations showed most hawks migrated to the eastern front of the Rocky Mountains or the northern plains in the fall, and wintered in central or southern California. Ground reconnaissance at fall sites where adult hawks remained 4 to 10 weeks found hawks primarily associated with populations of Richardson’s ground squirrels (Spermophilus richardsoni) and pocket gophers (Thomomys spp.) in native prairie habitats or on edges of cultivated land. Three of 9 adult hawks (30%) were confirmed or suspected mortalities during the winter of 2000. In 2001 we deployed 4 PTTs on juvenile hawks to better understand their movements and survival. We plan to continue deployment of PTTs on juvenile hawks in 2002.