Swainson’s Hawk

Identification

Swainson's hawk is a medium-sized raptor in the genus Buteo, measuring 43–56 cm long with a wingspan of 117–137 cm. It is slightly smaller than the related red-tailed hawk but has proportionally longer, more slender wings. Females are noticeably larger than males, averaging 1.15 kg compared to males at 0.81 kg. In flight, the hawk characteristically holds its wings in a slight dihedral and tips gently back and forth while soaring, using thermals to gain altitude before gliding to the next rising air current.

Over 90% of individuals display light-morph plumage: white underparts with a distinctive dark reddish "bib" on the chest, a noticeable white throat and face patch, and brown upperparts. The underwings show a unique pattern among North American raptors—light linings along the leading edge contrasting with dark flight feathers on the trailing edge. The tail is gray-brown with narrow dark bands. Dark-morph birds, more common in the far west, are dark brown overall with a light patch under the tail. Juveniles resemble adults but have pale mottling on dark areas and dark mottling on light areas, particularly the flanks.

Range & Habitat

Swainson's hawk breeds across western and central North America, from east-central Alaska and southwestern Yukon south through the Great Plains and western states including Washington, Oregon, California, Arizona, New Mexico, Colorado, and Texas. Its breeding range extends eastward through Minnesota, Iowa, Nebraska, Kansas, and Oklahoma. The species favors prairie and dry grasslands for breeding, constructing stick nests in trees, shrubs, or on cliff edges. It is a long-distance migrant, wintering predominantly on the pampas of South America in Argentina, Uruguay, and southern Brazil. Small populations occasionally winter in southeastern Florida and along the Texas coast.

Behaviour & Diet

Swainson's hawk is colloquially known as the grasshopper hawk or locust hawk, reflecting its voracious appetite for Acrididae (locusts and grasshoppers), which it eats whenever available. This species is the second longest migrant of any North American raptor, with flights from breeding grounds to South American wintering grounds spanning up to 7,100 miles and lasting at least two months. Migration occurs from August to October, with birds departing on clear days with favorable winds. They navigate by soaring in thermal currents, gaining altitude in circles before gliding with closed tails until finding the next rising air mass.

During migration, populations funnel through the Isthmus of Panama in spectacular concentrations. In the Andes, birds follow a narrow migration corridor with remarkable consistency, though occasionally individuals become lost and are recorded far from their usual routes. Interestingly, recent research suggests that Swainson's hawk is the ancestor of the Galápagos hawk, which diverged from mainland populations approximately 300,000 years ago—a remarkably short timeframe in evolutionary terms.

Best Time & Places to See It

Spring and summer offer the best opportunities to observe Swainson's hawks on their breeding grounds across the western and central prairies of North America. For witnessing the spectacular long-distance migration, the Isthmus of Panama—particularly locations like Ancon Hill, Balboa, and Panama City—offers concentrations of birds that are truly remarkable. Birders and wildlife enthusiasts visiting breeding areas should scan open grasslands and prairies during daylight hours when hawks are actively soaring and hunting.

Photography Tips

Photograph this soaring raptor during clear, warm days when thermal activity is highest and birds are most active. The distinctive silhouette in flight—with slightly raised wings in a dihedral posture and characteristic gentle rocking motion—is highly photogenic. Capture the unique underwing pattern by positioning yourself below soaring birds to showcase the light wing linings contrasting with dark flight feathers. The light-morph bird's striking white underparts and dark reddish chest patch provide excellent contrast for photography. During migration concentrations, use higher shutter speeds to freeze the rapid wing movements as birds navigate thermals.