Swainson's Hawk

Swainson's Hawk

Buteo swainsoni
L 17-22 / WS 47-54

Swainson's Hawks are birds of the West, nesting in open country habitats including Pinyon-juniper, Sagebrush grasslands, agricultural areas, and riparian corridors. They nest in large deciduous trees or junipers depending on availability, or on power poles. Swainson's Hawks are territorial on the breeding grounds, but share territories where pair densities are high. They are large birds, only slightly smaller than Red-tailed Hawk, but hunt mainly rodents and insects, and also small birds and snakes. Swainson's Hawks are fairly common breeders across much of their range from northern Mexico to central Canada and west to California. They are localized in the northern part of their range, and rare in Alaska. Swainson's Hawks become uncommon along the eastern Great Plains with a few pairs breeding east to Illinois.

Swainson's Hawks congregate outside the breeding season in places where food resources are plentiful, especially flooded fields (particularly alfalfa) where mice are forced out of their burrows, and other agricultural areas. It is not uncommon to see large groups on the ground following tractors that turn up rodents and insects. During migration and winter they are gregarious, often forming large kettles at various migration sites in Texas, Mexico, and Panama. Swainson's Hawk's call is similar to Red-tailed Hawk but less raspy and higher-pitched. Juvenile gives a high-pitched, repeated, begging "whiw, whiw, whiw, whiw."

Shape

  • Perched, are robust with long wings that reach tail rip.
  • Wings are long but slimmer than Red-tailed and pointed at all times. Wing shape is most similar to Broad-winged Hawk, but longer, and more elegant.
  • Gliding overhead, wings appear falcon-like, sharply pointed and projecting well past back edge of the wings creating an M-shaped silhouette.
  • When gliding at eye level, wings droop and appear Osprey-like, but shorter and more pointed.

Flight

  • Elegant, amazing aerialists with light, buoyant flight, especially when catching insects on the wing. Hover and kite with ease as well.
  • Soaring, teeter from side-to-side similar to Harrier and with strong dihedral, but more stable and surprisingly flat-winged on light winds.
  • Typically glide with modified dihedral.
  • Flap with easy wing beats, but with stiffness and power. Adult can flap with shallow almost Red-tailed Hawk-like wing beats.

Plumage

  • Three age classes, adult, sub-adult, and juvenile. Plumage ranges from whitish to dark body below, with contrasting dark flight feathers. A cline from light to dark exists, and many birds are difficult to assign a color morph. Sexes overlap in plumage.
  • Light-morph adult whitish underneath with dark bib on chest, and dark flight feathers, appearing strongly two-toned. Topside is blackish-brown with paler uppertail coverts. Eyes are dark brown.
  • Juvenile is orangey to whitish underneath, lacks a bib, and is faintly to moderately streaked on chest with slightly paler flight feathers. Juvenile has pale-fringed upperwing coverts and pale head. Eyes are pale to light brown.
  • Sub-adult similar to juvenile underneath but typically more heavily marked with adult-like upperside and flight feathers. Head of juvenile and sub-adult can be whitish by spring due to fading. Eyes are light brown.
  • Dark-morph is either wholly dark rufous underneath or rufous-barred belly with dark brown chest (adult), or heavily streaked throughout (juvenile and sub-adult). The underwing coverts are whitish with rufous mottling to solid rufous. Almost every Swainson's Hawk has pale undertail coverts, except a few dark extremes. Dark extremes are the only birds to lack a distinct two-toned appearance below.

Migration

  • Long-distance migrant, wintering primarily in Argentina, but regular small populations wintering in FL, TX, and CA.
  • Rare along Great Lakes and East Coast in spring and fall.
  • Can be seen in large kettles on migration, especially along Texas coast and Veracruz, Mexico. In smaller groups throughout parts of the West.
  • Spring migration generally from late March to May, and September through November in fall.
  • California breeders arrive from late February to March and depart from September to early October.

Distribution

(Map from Cornell Lab of Ornithology's All About Birds. For dynamic distribution maps, visit the eBird website.)

Swainsons map