Qualifies for the list as a Rare Yellow List Species

Photo: USFWS

The Swainson’s Hawk breeds in western North America, from Canada to northern Mexico and from Washington and Oregon east of the Cascades east to the Great Plains. Favored habitat is open stands dominated by grass, sparse shrublands and small and open woodlands. It typically nests in scattered trees within this habitat. It also has adapted to foraging in some agricultural areas, particularly where the crops are wheat and alfalfa. It winters in South America, particularly on the pampas of Argentina; the round-trip between breeding and wintering areas is as much as 20,000 km. It is gregarious in migration and migrates in large flocks sometimes numbering in the thousands. During breeding the young are fed on a vertebrate diet, but unlike other raptors, during nonbreeding the Swainson’s Hawk feeds almost exclusively on insects, particularly grasshoppers in grasslands or harvested fields.

Though still wide-ranging and common, its numbers have fallen significantly in the western Canadian prairie, where its main prey, Richardson’s Ground squirrel, has declined. It has also declined in the western U.S. A cause for decline has been heavy mortality brought about by use of the pesticide monocrotophos in Argentina; these practices need to be changed to conserve the bird. Once persecuted as a nuisance species despite the fact that it feeds on agricultural pests, the bird is considered to be declining in Utah, Nevada and Oregon, and the California population has been reduced by as much as 90% in historical times.