Swainsons Hawk (Buteo swainsoni)

Swainsons Hawk

[order] ACCIPITRIFORMES | [family] Accipitridae | [latin] Buteo swainsoni | [authority] Bonaparte, 1838 | [UK] Swainsons Hawk | [FR] Buse de Swainson | [DE] Prariebussard | [ES] Busardo Chapulinero | [NL] Prairie-buizerd

Subspecies

Genus Species subspecies Region Range
Buteo swainsoni NA, MA nw, wc

Genus

Members of the genus Buteo are broad-winged, broad-tailed hawks, Well adapted for soaring. The bill, legs and talons are of average proportions. There is much colour variation both within the species, and, by way of phases, within individual species. In all cases the young are quite different from adults in that they are all well camouflaged with an overall brown appearance with varying amounts of striping below and paler mottling above.
The 25 species are spread worldwide with the exception of Australasia and much of the Indian sub-continent.

Physical charateristics

A buteo of the plains, proportioned like a Red-tail but wings a bit more pointed. When gliding, wings are held slightly above horizontal. Typical adults have a dark breastband. Overhead, buffy wing linings contrast with
dark flightfeathers. Tail is gray above, often becoming white at the base. There are confusing individuals with light breasts, and dark melanistic birds; note the underwing with its dark flight feathers. The Swainson’s Hawk is not, to many, the most impressive member of the Buteo genus. It tends to be (compared with, for example, the Red-tailed Hawk) rather lank and long-winged; a little sluggish in its habits and, although well able to soar with the rest of the genus, more likely to be found perched on a post, or even on the ground.

Listen to the sound of Swainsons Hawk

[audio:http://www.planetofbirds.com/MASTER/ACCIPITRIFORMES/Accipitridae/sounds/Swainsons Hawk.mp3]

Copyright remark: Most sounds derived from xeno-canto


wingspan min.: 124 cm wingspan max.: 137 cm
size min.: 48 cm size max.: 56 cm
incubation min.: 34 days incubation max.: 35 days
fledging min.: 42 days fledging max.: 44 days
broods: 1   eggs min.: 1  
      eggs max.: 4  

Range

North America, Middle America : nw, Westcentral. The Swainson’s Hawk breeds throughout western North America, in the plains and dry regions. A few move as far north as Aaska, and some as far south as Mexico – always in low or moderately high country. The favoured winter areas are the pampas of Argentina although some winter in Florida.

Habitat

Plains, dry grassland, farmland, ranch country.
Breeds most commonly on northern Great Plains, in prairie regions with scattered groves of trees for nest sites. Less common in dry grassland farther west and in heavily farmed country. In migration, often pauses in fields where insect lar
vae may have been turned up by the plow.

Reproduction

On prairies with scattered groves of trees, may have conflicts with Great Horned Owl where they attempt to nest in same grove.
Nest: Site is usually in tree or large shrub in open country, usually 15-30′ above ground, but may be lower or higher; generally well hidden within foliage. Sometimes nests on ledge of cliff or steep slope. Nest is a platform of sticks, lined with finer twigs, weeds. Often adds leafy green branches to nest. Clutch 2-3, sometimes 1 or 4. Pale bluish white fading to dull white, usually lightly spotted with brown. Incubation almost entirely by female, about 34-35 days. Male brings food to female during incubation.
Young: Both parents bring food for young, but at first, female may remain with young much of time while male hunts. Young can fly about 42-44 days after hatching; may remain with parents until fall migration.

Feeding habits

Mostly small mammals and reptiles in early summer, large insects at other seasons. When feeding young, preys on ground squirrels, pocket gophers, mice, snakes, lizards, small birds. At other seasons, mostly large insects. May feed heavily on grasshoppers and caterpillars in late summer. In winter in Argentina, follows and feeds on swarms of nomadic dragonflies. May hunt by soaring over grassland, or by perching and scanning the ground. Skilled at catching flying insects in the air. In fields, may catch insects by running about on ground.

Video Swainsons Hawk

httpv://www.youtube.com/watch?v=-0IkjNtmzLY

copyright: Matt Giovanni


Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
It is estimated that about 20,000 Swainson’s Hawks died during the winter of 1995-1996 through the use of a pesticide called monocrotophos in their Argentinean wintering grounds. The pesticide was used to control the grasshoppers and caterpillars which are the main food for the hawks (and numerous other species) when they are there. The good news is that there followed an international effort to solve the problem, involving Argentina, USA, Canada and Switzerland. The end result was that the chemical companies removed the monocrotophos from the area where the fatalities occurred. Argentina banned the use of monocrotophos nationally in March 2000
Swainsons Hawk status Least Concern

Migration

Highly migratory. Main non-breeding grounds (boreal winter) in Argentina; migration follows land route through Central America, with some scattered wintering grounds in other open habitats of Neotropics. Some autumn migrant flocks in Central America in 1000’s; total of 400,000 recently recorded over Veracruz, East Mexico. May fly without feeding between South USA and winter quarters in South America. Increasingly some birds winter in Florida, California and also Texas.

Distribution map

Swainsons Hawk distribution range map

Leave a Reply