Swainson's Hawk

Swainson's hawk (Buteo swainsoni), named in honor of the British naturalist William Swainson, is a large raptor of the Accipitriformes order. It is sometimes referred to as the grasshopper hawk or locust hawk due to its dietary preference for Acrididae, such as locusts and grasshoppers.

Identification Tips

This medium-sized Buteo species has a length of 43–56 cm (17–22 in) and weighs between 0.5–1.7 kg (1.1–3.7 lb). Females are slightly larger than males. Swainson's hawk is characterized by its long, slender wings, with a wingspan of 117–137 cm (46–54 in), and a distinctive flight pattern that includes soaring with a slight dihedral and tipping back and forth. There are two main color morphs: the light morph, which makes up over 90% of the population, and the dark morph, which is more common in the western part of its range. The light morph has a white underbody with a reddish "bib" on the chest, while the dark morph is predominantly dark brown with a light patch under the tail.

Habitat

Swainson's hawk favors open and semi-open landscapes such as prairies, grasslands, and deserts for both breeding and wintering. It requires elevated perches for hunting and is closely associated with the presence of small mammals.

Distribution

This species breeds in western North America, with its range extending from Alaska and Canada through the Great Plains down to Texas. It is a long-distance migrant, wintering in Argentina and occasionally recorded as a vagrant in Chile, the Dominican Republic, Trinidad and Tobago, and even Norway.

Behaviour

Swainson's hawk is known for its impressive migratory behavior, traveling up to 11,400 km (7,100 mi) to South American pampas. It migrates in large flocks, often using thermals to gain altitude before gliding southwards. The species is territorial during the breeding season but may gather in groups when feeding or migrating.

Breeding

Monogamous and exhibiting high mate fidelity, Swainson's hawks return to the same nesting sites annually. They build stick nests in trees, shrubs, or on cliff edges. Clutch size ranges from one to four eggs, with an incubation period of 34 to 35 days. Young fledge at about 38 to 46 days old and remain dependent on their parents for several weeks.

Similar Species

Swainson's hawk may be confused with the red-tailed hawk (Buteo jamaicensis) and the ferruginous hawk (Buteo regalis), but can be distinguished by its longer wingspan, flight pattern, and color morphs.

Diet and Feeding

While largely insectivorous, breeding Swainson's hawks switch to vertebrate prey to feed their nestlings. They employ various hunting methods, including still-hunting from perches and soaring. They are opportunistic feeders, often following agricultural equipment or wildfires to capture exposed prey.

Conservation Status

Swainson's hawk is currently listed as Least Concern by the IUCN. However, it has faced population declines due to pesticide use in its wintering grounds and habitat loss. Conservation efforts have been made to reduce pesticide-related mortality in Argentina.