Species Occurring on the Sioux District, Custer National Forest 



Swainson's Hawk (Buteo swainsoni) 



Distribution: Breeds locally in Alaska, the Yukon, and adjacent Macken2de District south to 

 northern Mexico, mostly west of the 100th meridian. Widespread during the breeding season 

 in Montana (Bergeron et al. 1992) and South Dakota (S.D. Omithol. Union 1991). Winters 

 primarily on the pampas of southeastern South America. 



Habitat Use: This is a hawk of open grassland and sagebrush, often seen perched on fence posts 

 and telephone poles. During summer, birds seem to prefer mixed and short-grass prairie 

 where they frequently forage for small rodents and insects. During the breeding season they 

 prey mostly on ground squirrels and pocket gophers in North Dakota (Gilmer and Stewart 

 1984), and ground squirrels and voles in Montana (Restani 1991). Density of nesting pairs 

 correlated with ground squirrel abundance in Alberta, Canada where grasslands are 

 interspersed with agricultural fields (Schmutz and Hungle 1989). 



Nest Sites: Prefers to nest in areas of open grassland with scattered trees. Swainson's Hawks are 

 more likely to be found nearer agricultural habitat or human habitation than other Buteos 

 (Bechard et al. 1990, Schmutz 1984, 1987). Wooded draws are considered important nesting 

 habitat in North Dakota (Gaines and Kohn 1982), where nests are placed in green ash or 

 American elm. In central North Dakota, 100% of 270 nests were in trees and 7.1 ± 3.3 m 

 above ground (Gilmer and Stewart 1984). In southeastern Washington, 100% of 67 nests 

 were in trees and 8.7 ± 0.5 m above the ground (Bechard et al. 1990). In southeastern 

 Wyoming, 43 nests were in trees, 5 in willow shrubs, and 1 on a telephone pole crossbar 

 (Dunkle 1977). In the Centennial Valley, Montana, >95% of nests were in willows (Restani 

 1991). While it nests lower in shorter trees than other Buteos in Alberta (Schmutz et al. 

 1980), the opposite is true in Oregon (Green and Morrison 1983). It will use artificial nest 

 platforms (Schmutz et al. 1984). Nests are relatively flimsy compared to other Buteo nests in 

 the region (Call 1978). 



Nest Success: Usually lays 2-3 eggs. Seven nests produced 8 fledglings in North Dakota 

 hardwood draws (Gaines and Kohn 1982); 1.6 young/active nest fledged in southcentral 

 North Dakota (Gilmer and Stewart 1 984); 1 .4 young/laying pair fledged in southeastern 

 Wyoming (Dunkle 1977); 42 nests produced 1.4 fledglings/active nest in Montana (Restani 

 1991). 



Breeding Phenology: Usually breeds later than other Buteo species in region; arrives in 

 Wyoming in late April (Dunkle 1977); nests in South Dakota May- July (S.D. Omithol. 

 Union 1991); average laying date mid-May in Montana (Restani 1991); eggs hatch in late 

 June to early July in Alberta (Schmutz et al. 1 980). 



Status: Expected to be fairly common and widespread in region; Becker (1978) suspected 

 nesting near the Carter County, Montana units of the Sioux District, but most (all?) pairs 

 probably nest off of Forest Service land. Numbers are increasing in Montana and North 

 Dakota, as it is more tolerant of agricultural landscapes than the Ferruginous Hawk (Dobkin 

 1994). White (1994), however, indicates that populations may be declining regionally, 

 particularly in California and Oregon. 



Natural Heritage Program rank: G4; S5B,SZN in Montana, S4B South Dakota. 



