Swainson’s Hawk

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Quick Facts

Migratory
  • Scientific Name: Buteo swainsoni
  • Spanish Name: Aguilucho langostero
  • Family: Accipitridae
  • Known Nicknames: Grasshopper Hawk, Locust Hawk
  • Average Length: 43–56 cm / 17–22 in
  • Average Weight: 510–1400 g / 1.1–3.1 lb
  • Wingspan: 117–137 cm / 46–54 in
  • Key Feature: Dark bib or hood contrasting with pale throat and chest; long, narrow, pointed wings
  • Primary Diet: Primarily Carnivore (insectivorous during migration, small mammals and birds on breeding grounds)
  • Range: Western North America (breeds); migrates to South America (mainly Argentina)
  • Habitat: Open grasslands, agricultural fields, and sagebrush steppe
  • Social Structure: Solitary during breeding; highly gregarious during migration (forms large kettles)
  • Nesting/Breeding: Trees, shrubs, or utility poles (stick nest)
  • Conservation Status: Least Concern (LC)
  • Population Trend: Stable

Swainson’s Hawk (*Buteo swainsoni*) is a sleek, long-winged raptor renowned for one of the most extraordinary migrations in the bird world, traveling up to 14,000 miles annually from North American grasslands to the Argentine pampas. In flight, it is often mistaken for a falcon due to its pointed wings and narrow tail, but its general appearance varies dramatically: adults typically display a dark brown back, a pale belly with a distinctive dark "bib" across the chest, and a white throat, while a rare dark morph appears nearly black. A unique characteristic is its dietary shift—during the breeding season it hunts rodents and insects like grasshoppers, but on migration, it forms massive flocks (called "kettles") and switches almost exclusively to catching dragonflies and other aerial insects. Its piercing, high-pitched call and habit of perching on fence posts or hovering over fields make it a iconic sentinel of open country, though habitat loss has led to conservation concern in some regions.

Fun Facts

Swainson’s Hawks are famous for their epic migration, traveling up to 14,000 miles each year from North America to the Argentine pampas—one of the longest raptor migrations on Earth. During this journey, they form massive communal flocks called “kettles” that can number in the thousands, spiraling together on thermals. Quirkily, they shift their diet dramatically: in summer, they hunt rodents and reptiles like typical buteos, but on their wintering grounds in South America, they become insect specialists, following tractors and grass fires to feast on grasshoppers and dragonflies. They also have a unique adaptation called “buccal fluttering,” rapidly vibrating their throat membranes to cool down in extreme heat, a behavior rarely seen in other raptors.

Habitats & Distribution

Swainson's Hawk occupies open habitats across western North America, favoring shortgrass prairies, sagebrush steppes, agricultural fields, and arid grasslands with scattered trees or utility poles for perching. Its breeding range extends from Alaska and western Canada through the Great Plains and Intermountain West, south to northern Mexico. During the non-breeding season, it undertakes one of the longest migrations of any North American raptor, traveling to the pampas and open grasslands of central Argentina, Uruguay, and southern Brazil, wintering in similar lowland agricultural and pasture environments.

Behaviours & Reproduction

Swainson’s Hawks are generally monogamous, forming pair bonds that often last for multiple breeding seasons. They are highly social during migration, forming large flocks called kettles, but become territorial when nesting. Courtship involves dramatic aerial displays, including mutual soaring, high-speed dives, and the male passing food to the female in mid-air. They typically nest in isolated trees or on cliffs, constructing a bulky stick platform lined with softer materials. A unique reproductive strategy is their strong fidelity to both nesting sites and wintering grounds in the pampas of South America, returning to the same locations year after year. The female lays two to four eggs, which she incubates for about a month while the male provides food; after hatching, both parents feed the young, which fledge at around six to seven weeks but remain dependent for several more weeks.

Diet

Swainson's Hawk has one of the most remarkable dietary shifts of any raptor, transitioning from a rodent-heavy diet during the breeding season to an almost exclusively insectivorous diet on its wintering grounds. While nesting in North America, it primarily hunts ground squirrels, pocket gophers, and young jackrabbits, often capturing them by soaring low over grasslands and dropping onto prey. However, during migration and throughout its winter stay on the Argentine pampas, it becomes a specialist on grasshoppers, crickets, beetles, and dragonflies, frequently foraging in large flocks that follow swarms of insects. An interesting fact is that Swainson's Hawks will also gorge on Mormon crickets during massive outbreaks, and they have been known to follow agricultural machinery to catch rodents and insects flushed from fields. Additionally, they occasionally consume snakes, lizards, and even small birds, but their diet is uniquely flexible compared to other Buteo hawks, allowing them to thrive across vastly different ecosystems.

Colors

Swainson's Hawk exhibits highly variable plumage, ranging from light to dark morphs. Light morphs have a dark brown back, white underparts, and a distinctive dark bib across the chest, while dark morphs are uniformly sooty brown. All morphs show a two-toned underwing pattern with pale flight feathers contrasting with dark wing linings, and a white undertail coverts patch. Their coloration provides camouflage against open grasslands and agricultural fields during hunting.

Distribution Map

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