| We used satellite telemetry to assess migration and wintering patterns of Swainson's hawks (Buteo swainsoni) that breed in California's Central Valley (CV). We tracked 20 birds captured on breeding sites near Sacramento for a total of 30 fall and 31 spring migration trips and 28 winter seasons. CV hawks wintered in four regions spread across 7,200 square kilometers: western Mexico (25%), Central America (15%), northern South America (40%), and central South America (20%). Hawks wintering in southern locations spent more time migrating, arrived later at wintering areas, departed earlier for spring migration, and arrived later at breeding areas. During fall migration, hawks spent an average of 55 days at stopover locations, mainly in four areas: San Joaquin Valley, Sonoran Desert, northwest coastal Mexico, and central-western Mexico. Spring migration was much more direct, with an average of only three days of stopover. Most stopover and wintering areas were agricultural lands. Results suggest a recent and ongoing shift in wintering areas to more northern agricultural lands. The migration routes and wintering areas of CV hawks differ from, and are more diverse than, those of the much larger interior North American Swainson's hawk population.
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