Buteo swainsoni
Swainson’s Hawk
The Swainson’s Hawk is a medium-sized bird of prey that inhabits open country grasslands, shrub-steppes, deserts, and agricultural areas of western North America during the breeding season and winters in grassland and agricultural regions extending from Central Mexico to southern South America (England et al. 1997, Bradbury et al. in preparation). Early accounts described the Swainson’s Hawk as one of the most common raptors in California, occurring throughout much of the lowland areas of the state (Sharpe 1902).
With the conversion of native grassland foraging habitat and the loss of riparian forest and oak woodland nesting habitat, the statewide population was reduced substantially. Currently, there are an estimated 700 to 1,000 breeding pairs in the state (Swainson’s Hawk Technical Advisory Committee file data), representing less than 10 percent of the historic population (Bloom 1979).
The Central Valley population (between 600 and 900 breeding pairs) extends from Tehama County southward to Tulare and Kings Counties. Despite the loss of native habitats in the Central Valley, the Swainson’s Hawk appears to have adapted relatively well to certain types of agricultural patterns in areas where suitable nesting habitat remains. The optimal foraging and nesting habitat conditions in Yolo and portions of Sacramento and San Joaquin counties support the bulk of the Central Valley Swainson’s Hawk population (Estep 1989, Estep in preparation).
The Swainson’s Hawk is listed as threatened under California Endangered Species Act and is a federal species of conservation concern (USFWS 2008).
Swainson’s Hawk 1: Jim Morris
Swainson’s Hawk 2: Sharon Barker
