California Raptor Center

Swainson's Hawk

Scientific Name: Buteo swainsoni
(Buteo is Latin for hawk, swainsoni –Named after the English naturalist WilliamSwainson) 

Size: Length: 17-22in Wingspan: 47-54in

Weight: Female: 1069g (~2.4lb) average Male: 908 (~1.9lb) average

Lifespan: In the wild may live 15 years or more and in captivity may live to 20 years or more.

ID: This hawk's most unique feature is its variation in color. The light color morph includes white patches on the forehead, the throat and the belly. The rest of the body is a dark brown. The dark color morph, which is the less common type, includes an entirely dark brown body with only a white patch under the tail. Other variations between these two distinct extremes have been observed. In adults the breast is much darker than the belly. They have a “negative” wing effect which means that they have dark flight feathers and light coverts. The juveniles look similar to the adults but are more buffy and streaky than the adults.

Hunting: Swainson’s hawks hunt from perches and on the wing.

Prey: In the summer they prey on small mammals and insects, and occasionally reptiles, snakes, and birds.  They are known for their tendency to follow tractors in agriculture areas, waiting for the machines to scare up prey. During migration and on the wintering grounds the birds mainly eat insects.   

Breeding: They build very flimsy stick nests in trees. The Swainson's Hawk starts the breeding season by building nests in March and April. The nest is usually found in trees, shrubs, on the ground, or on top of utility poles. These hawks are mostly mongamous, so a breeding pair may return to a previous nesting site. When the nest is complete, the female lays 2 to 4 eggs. The male usually helps the female with the incubation, which lasts for about 30 days. The young hatch between March and July, and stay in the nest for another 30 days. While most juveniles migrate the following winter with their parents, there are some groups that do not migrate their first winter.

Range: Swainson’s Hawks are complete migrators.  They have perhaps one of the longest migrations: from their breeding grounds in North America to their summering grounds in South America.

Status: Currently they are a Federal Species of Concern, and also considered threatened by the state of California.