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We studied nest site land cover associations, and reproductive success of two Buteo species of conservation concern on the southern Great Plains, USA. The study area was in Cimarron County, Oklahoma, where land use is dominated by row crop agriculture, livestock grazing, and Conservation Reserve Program grasslands. Ferruginous Hawks (B. regalis) were uncommon and nested primarily in and around the Rita Blanca National Grassland (NG). Swainson’s Hawks (B. swainsoni) were common and nested throughout the study area. Ferruginous Hawks territories contained more sandsage and less cropland and CRP than random sites, whereas Swainson’s Hawk territories mirrored the available landcover. Our results suggest that the availability of sandsage habitat is an important factor in determining nesting density (Ferruginous Hawks) and reproductive success (Swainson’s Hawks) on the Southern High Plains. Nest site availability also may have constrained the distribution of Buteos in our study area and is probably a major factor limiting Ferruginous Hawk nesting density. Ferruginous Hawks typically nest on man-made platforms (nest platforms and windmills) that were most common in and around the Rita Blanca National Grasslands. Our results suggest that conversion of native grasslands to cropland has had negative consequences for Ferruginous and Swainson’s Hawks. This relationship has been previously demonstrated in several studies of Ferruginous Hawks, but not for Swainson’s Hawks. In particular, loss of sandsage habitats on the southern High Plains may have contributed to range declines in Ferruginous Hawks and decreased breeding success for Swainson’s Hawks. Swainson’s Hawk reproductive success should be monitored in other areas of the Great Plains to obtain information on the factors affecting breeding success and regional population declines.
