The Swainson's Hawk

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The Swainson's Hawk is a large bird measuring 18 to 22 inches in length with a wingspan of up to 4 feet. When perched, the wings will extend beyond the tip of the tail.

It has a dark brown head and back with a light brown chest and a white belly. It has a dark 'bib' on its chest and a noticeable white throat patch. The underside of the wings has a dark leading edge with lighter feathers along the trailing edge. The gray-brown tail has six narrow dark bands and one wider subterminal band. The male and female are similar in appearance.

The Swainson's Hawk return to their nesting sites in March or April. Shortly after arriving the male builds a nest. If the old nest still exists, the male will refurbish it rather than start from scratch. The nest is made of twigs and grass, and can be built on the ground, on a cliff ledge, or in a tree. A new nest will take up to 2 weeks to build.

The mating rituals of the Swainson's Hawk are not well known, but it does involve circling and diving displays above the nest site and a lot of vocalization. Once paired, the Swainson's Hawk shows a high degree of mate and territorial fidelity.

The clutch consists of 2 to 3 white elliptical shaped eggs. The female incubates the eggs for 34 to 35 days depending on her mate for food. The young leave the nest for short flights 33 to 37 days after hatching. The fledglings are dependent on their parents for another 4 to 5 weeks after that. The pair produces one brood a year and will not lay a replacement clutch if something happens to the first. They frequently suffer egg loss due to owl predation, and unexplained egg infertility.

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The Swainson's Hawk is called the 'grasshopper hawk' for a reason. Except when nesting, the Swainson's Hawk is an insectivore. Their diet is predominatly grasshoppers, crickets and locusts. While nesting they will prey on ground squirrels, rabbits, gophers and mice. Small birds, reptiles, and injured water fowl have also been taken as prey by the Swainson's Hawk.

When on the hunt, the Swainson's Hawk uses several different strategies. It will pluck dragonflies and grasshoppers out of the air or follow along behind farm equipment feeding on the insects it stirs up. When hunting larger prey, it will scan the area around it from a perch. Once prey is spotted, its swoops down grabbing it with its foot and then immediately transferring it to its beak.

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The Swainson's Hawk is a common bird in western North America. It prefers the open and semi-open grasslands such as hayfields, pastures, and alfalfa fields. They are a migratory bird preferring to winter in Argentina or the pampas of South America.

Outside of mating season, the Swainson's Hawk is relatively quiet. Its call is a shrill, kr-e-e-e-e-e-e.

The Swainson's Hawk's numbers have declined over the years partially due to loss of habitat. Although DDT has been banned in the United States, the Swainson's Hawk is still exposed to it in some of its wintering grounds. DDT has been shown to cause a thinning of the egg shells and that may be contributing to the Swainson's decreasing numbers. It is currently on the National Audubon's List of Special Concern and on the California Department of Fish and Game's threatened species list. It is not currently on the Federal list of threatened or endangered list.