Adult Turnover, Productivity, and Nest-Tree Status of Swainson's Hawks in and Adjacent to the Snake River Birds of Prey National Conservation Area

Swainson's hawks (Buteo swainsoni) nest in grassland, shrubland, and agricultural areas throughout western North America (England et al. 1997). They typically nest in scattered trees of a variety of tree species including locusts (Robinia spp.), aspens and poplars (Populus spp.), and willows (Salix spp.). They eat mostly rodents such as ground squirrels (Spermophilus spp.), pocket gophers (Thomomys spp.), and voles (Microtus spp.), and breeding pairs become concentrated in agricultural areas where hay and pastureland support dense populations of ground squirrel and microtine prey (England et al. 1979). In areas of high prey numbers, the availability of suitable nest trees becomes a critical factor in limiting the density of nesting populations, particularly in the more arid areas of the West.