During migration, nearly all Swainson's hawks funnel through which Central American land bridge?

During migration, nearly all Swainson’s hawks funnel through the Isthmus of Panama. This narrow land bridge connects North and South America and concentrates the species’ southbound movement before the birds continue toward their wintering grounds in South America.

Swainson’s hawks breed across open country in western and central North America, including parts of Canada and the United States. Most winter on the pampas of Argentina, Uruguay and southern Brazil. Their full journey can reach about 7,100 miles, making them among North America’s longest-distance raptor migrants.

The hawks conserve energy by riding rising thermals. They circle upward, then glide southward until they find another thermal, forming spectacular streams and flocks. Panama’s geography helps funnel these soaring migrants into especially visible concentrations near places such as Ancón Hill and Panama City.

The Isthmus of Panama is not the same as the Darién Gap, which is a difficult roadless region farther southeast along the land bridge. Nor is the route centered on Mexico’s Yucatán Peninsula or the Isthmus of Tehuantepec. California-breeding birds may follow a different route and winter in Mexico or Central America.