The Swainson’s Hawk is a medium sized Buteo that breeds in the high plains of central western North America. Almost all of the population winters in the grasslands of southern South America in northern Argentina, Paraguay and southern Brazil. This migration constitutes one of the longest seasonal movements of any New World raptor. The migration through Central and South America follows a land route through a narrow corridor south along the east coast of Mexico; crossing over the Isthmus of Tehuantepec to the Pacific Coast; south through Central America; crossing the Andes in central Colombia; and across the western Amazon Basin and the chaco to the wintering grounds. Apparently much the same route is taken on both north and south bound migrations. When breeding, Swainson's Hawks primarily prey on small mammals, but when wintering they feed mostly on insects, and often will congregate in large flocks where prey is particularly abundant.