Swainson’s hawks that breed in western North America mainly winter in Argentina.
These long-distance raptors breed across open country from western Canada and Alaska south through the western United States. When autumn arrives, they migrate south through Mexico and Central America, with many birds funnelling through the Isthmus of Panama before crossing into South America.
Argentina’s Pampas provide extensive grassland and farmland where the hawks spend the austral summer. They also winter in Uruguay and southern Brazil, so Argentina is the best single-country answer rather than the only country in their winter range. Birds from California’s Central Valley can follow a different route and winter in western Mexico or Central America.
Swainson’s hawks are famous for soaring migration: they circle upward on thermals, then glide to conserve energy. Their common names, grasshopper hawk and locust hawk, reflect their habit of eating large numbers of insects, especially on the South American wintering grounds.