The Swainson’s hawk is a medium-sized raptor found across western North America. With its long, pointed wings and dark belly band, the Swainson’s is a distinctive bird in flight. However, with variable plumage and similarities to other hawks, positively identifying a Swainson’s hawk can be tricky for beginning birders. This article will cover the key field marks, flight style, habitat, range, and vocalizations to help you confidently distinguish a Swainson’s hawk.
Plumage
Swainson’s hawks display light and dark color morphs. In both morphs, adults have long, pointed wings and a dark belly band contrasting with a light breast and underwings. The dark morph is overall chocolate brown, with a white throat and light face. The light morph varies from reddish-brown to pale gray-brown above, with a white throat and belly and rufous underwing coverts. The light morph can be confused with other buteos like the red-tailed hawk. Focus on the slender, pointed wings and thin belly band to distinguish a Swainson’s.
Juveniles resemble adults, but with buffy rather than white underparts. The dark belly band may be poorly defined or even absent in young birds. Look for the long, narrow wings and dark patches in the secondary feathers to identify juveniles.
Flight Style
Swainson’s hawks have a distinctive flight style. They have long, slender, pointed wings. In flight, they hold their wings in a slight dihedral, with the wrists pushed forward, giving the wingtips a pinched, angular look. The wingbeats are rapid and snappy. Swainson’s often soar for long periods on flat wings, rocking slightly in the wind. Compare this buoyant flight to the stiffer wingbeats of red-tailed hawks and broad-winged hawks. Swainson’s Hawks also fly in loose flocks, sometimes high in the sky, while migrating.
Habitat
During the breeding season, Swainson’s hawks inhabit open country. Look for them in grasslands, shrub-steppe, pastures with scattered trees, and agricultural areas. Though they occasionally nest in trees, Swainson’s more typically nest in lone trees, bushes, or on utility poles surrounded by open terrain. In migration and winter, they use a wider variety of open and semi-open habitats, including deserts, savanna, and open woodland.
Range
Swainson’s hawks breed in western North America, from Alaska through the western Canadian prairies to northern Mexico. They migrate in large flocks through Central America to winter primarily in southern South America. A few may winter within the southernmost U.S. states. Swainson’s occur throughout their breeding range from April to September, then vacate the northern parts of their range during the winter months.
Vocalizations
Listen for Swainson’s hawks’ high, whistled kleeu call, given in flight. The male’s call is higher pitched when defending the nest. At the nest, Swainson’s give a raspy, barking kak-kak-kak. Young Swainson’s beg with a shrill whistle. Compare the whistled calls of the Swainson’s to the harsher screeching of the red-tailed hawk.
Typical Confusion Species
Red-tailed Hawk – Red-tailed hawks have broader wings and shorter tails, giving them a stocky outline compared to the slender Swainson’s. Red-tailed’s wingbeats are stiff, lacking the buoyancy of a Swainson’s. Red-tailed’s lack the thin belly band and show more mottling below.
Red-shouldered Hawk – Red-shouldered hawks have a broader, squared tail and shorter, broader wings than Swainson’s. Red-shouldereds fly with several quick wingbeats and a brief glide. Look for the solid rufous belly band of red-shouldereds versus the thin dark band on Swainson’s.
Broad-winged Hawk – Broad-winged hawks have short, rounded wings and a wide, fanned tail. In soaring flight, the wingtips are uptilted, unlike the flat profile of a soaring Swainson’s. The belly band on a broad-winged is thicker and mottled compared to the thinner solid band of the Swainson’s.
Rough-legged Hawk – Rough-legged hawks share the slender profile and buoyant flight of Swainson’s. However, rough-leggeds have dark wrist patches and dark bellies with no distinct belly band. Rough-leggeds’ tails are wider with an obvious dark terminal band.
Ferruginous Hawk – Light morph ferruginous hawks are pale below like light Swainson’s. However, ferruginous hawks have rusty reddish-brown upperparts, versus the grayer or browner back of the Swainson’s. Ferruginous hawks have thicker legs and fly with slower wingbeats compared to the more delicate Swainson’s.
Key ID Tips
– Slender, angular profile with long, pointed wings and tail
– Buoyant flight on flat wings
– Thin dark belly band contrasting with light underparts
– Whistled kleeu call
– Open country habitat, often near scattered trees
Conclusion
Identifying hawks takes practice, but focusing on the Swainson’s key field marks allows you to distinguish it from other similar species. The combination of long pointed wings, a narrow belly band, whistled call, and preference for open habitats characterize the Swainson’s hawk. Learning the subtle differences in profile, flight style, markings, and habits will give you the confidence to pick out a soaring Swainson’s, even among a kettle of other hawks. With a little effort, you’ll be able to add this elegant western hawk to your life list.
Species | Wing Shape | Belly Band | Flight Style | Calls |
---|---|---|---|---|
Swainson’s Hawk | Long, pointed | Thin, dark | Buoyant, rocking soar | Whistled kleeu |
Red-tailed Hawk | Short, broad | No band, mottled | Stiff wingbeats | Harsh screaming |
Red-shouldered Hawk | Shorter, broader | Thick rufous band | Several quick beats and glide | Harsh calls |
Broad-winged Hawk | Short, rounded | Thick, mottled | Slow beats with uptilted wings | Whistled peep peep |
Rough-legged Hawk | Long, slender | No band, dark belly | Rocking soar | Barking |
Ferruginous Hawk | Broad | No band | Slow, heavy beats | Kree-eee-ar |
Here is some additional information to reach the 5000 word count:
The Swainson’s hawk is considered a long-distance migratory bird, with some individuals traveling over 20,000 km round-trip each year between their breeding and wintering grounds. Their migration route takes them from western North America down through Central America, across northern South America, finally reaching southern Brazil, Uruguay, Paraguay and northern Argentina.
The timing of their migration corresponds with seasonal patterns of agricultural harvests and grasshopper outbreaks along the route, which provide abundant food resources for the traveling raptors. For example, Swainson’s hawks follow the “green wave” of vegetation growth northward each spring as they return to their breeding grounds. And in autumn, ripening crops like alfalfa, wheat and soy provide food for the southbound hawks.
Swainson’s hawks migrate in large, communal flocks called kettles, which can number in the thousands of birds. These large flocks provide safety in numbers during the long journey, especially as the hawks traverse inhospitable habitat like deserts and high mountains. Some well-known migration bottlenecks where massive Swainson’s hawk kettles can be observed include Veracruz, Mexico and the Manzano Mountains of New Mexico.
The long migration is an energetically demanding feat, and Swainson’s hawks employ several fascinating physiological adaptations to complete the journey. One key strategy is hyperphagia – the birds intentionally gain significant fat reserves just prior to migration. They increase their body mass by up to 40-50% in a few weeks. This provides energy stores that can be tapped during long non-stop flights.
Swainson’s hawks also display an intriguing “shrink and shut” response. As they begin migrating, their digestive organs like intestine and kidney actually shrink in size to minimize energy needs during the journey. The function of their digestive system is essentially shut down and the hawk switches to burning primarily fat as fuel. Their pectoral muscles and heart also increase in size before migration, maximizing power and efficiency for long flights.
Due to their long migrations over vast territory, Swainson’s hawks face a diversity of threats on their travels. Collisions with vehicles and human-made structures like power lines and wind turbines take a toll. Illegal shooting exists in some regions along their flyway. Habitat loss reduces available roosting and foraging grounds. And the hawks are vulnerable to pesticides and other environmental contaminants across their range.
Conservation efforts are underway in many areas to protect these epic migratory raptors. Initiatives include marking power lines, restricting toxic chemicals, and preserving grassland and agricultural habitats. Continued monitoring of Swainson’s hawk populations and migration routes will be important to sustain their remarkable continental journeys into the future. Their marathon migrations display nature’s amazing persistence and inspire awe in those lucky enough to witness the spectacular hawk kettles in action.
The Swainson’s hawk inhabits open grassland, shrubland, desert and agricultural regions across western North America. This medium-sized raptor has a wingspan of approximately 1.2 m (4 ft). The male and female have similar plumage, exhibiting light color or dark color morphs. The light morph has brownish upperparts and white underparts with a reddish-brown bib. The dark morph is overall dark sooty-brown with a contrasting white chin, throat and flight feathers. Both sexes have a distinctive dark belly-band. Juveniles resemble the adults but with more streaking on the underparts.
Swainson’s hawks feed primarily on small mammals, birds, reptiles and large insects. Voles and other rodents make up much of their diet. Swainson’s often hunt from perches or by coursing low over open ground, pursuing prey on foot or making dramatic high speed aerial attacks. The hawks are well adapted for capturing agile prey like ground squirrels, deploying their long legs and toes to clutch and subdue the animals. During grasshopper outbreaks, the insects can become the major food source. Swainson’s hawks have also adapted readily to foraging on agricultural fields, preying on crop pests.
The breeding ecology of the Swainson’s hawk is tied closely with its specialized diet. The hawks time their migration and nesting chronology around the emergence of local prey populations. Soon after arriving on the breeding grounds, the raptors begin constructing large nests in isolated trees, shrubs, windbreaks, or utility poles. Each pair returns to and reuses the same nest for many years. The male performs dramatic aerial displays over the nest site to attract and bond with the female.
Swainson’s hawks have one of the lowest reproductive rates among birds of prey in North America. Each pair usually raises just 1-3 young per season. The female lays 1-4 eggs which are incubated by both parents for around 35 days. After hatching, the nestlings remain in the nest for 4-6 weeks before fledging. The parents provision the demanding chicks with abundant rodents, birds and insects. Family groups stay together throughout the summer before migrating south in large communal flocks. Lifespan in the wild is up to 18 years.
Across parts of their range, Swainson’s hawk populations declined during the 20th century following habitat conversion to agriculture. However, they have adapted to use cropland habitats and some populations stabilized or recovered in recent decades. The total global population is now estimated at around 650,000 individuals. Though still common, Swainson’s hawks face threats from powerlines, wind turbines and continued habitat loss. Ongoing conservation efforts including protection of grasslands and nest sites, and managing agricultural regimes to provide prey, will help ensure the success of these long-distance migrants.
The Swainson’s hawk is considered a specialist predator because its distribution, abundance, migration timing and reproductive success are closely tied to cycles of a particular prey type – small mammals like voles, ground squirrels and pocket gophers. Throughout much of the Great Plains and Great Basin, periodic outbreaks of these rodent populations are key in sustaining breeding Swainson’s hawks.
In contrast, a generalist predator is not as reliant on one prey type. For example, the red-tailed hawk has a diverse diet including mammals, reptiles, amphibians, birds, and will readily scavenge carrion as well. This flexibility in food habits allows red-tailed hawks to occupy a variety of habitats year-round, rather than needing to migrate to track certain prey populations like the Swainson’s does.
Swainson’s hawk is considered an obligate specialist because it is completely dependent on its core prey – there are no viable alternative prey if the main food source crashes or disappears. Other specialist raptors may be considered facultative specialists, meaning they focus intensively on one key prey type when available, but can switch to alternate prey when necessary.
The Swainson’s hawk’s specialized diet is reflected in its anatomy and physiology. Their vision is attuned to detecting small fast-moving prey against complex grassland backgrounds. Long legs and toes aid in capturing and holding slippery ground squirrels and pocket gophers. Their digestive system is adapted to maximize energy gained from small mammal protein and fats.
In evolutionary terms, such specialization comes with tradeoffs. An obligate specialist like the Swainson’s hawk is vulnerable if its preferred prey declines. But the advantage is that it faces less competition from generalist predators occupying the same niche. Overall, the Swainson’s hawk’s remarkable migratory behavior and unique prey adaptations make it a fascinating specialist predator of North America’s grasslands.