INTRODUCTION 



Interest in raptors became widespread in the 1 970s when it was realized that many species 

 were exhibiting dramatic population declines. At the time, reproduction of some species was 

 reduced due to eggshell-thinning. Thinning of eggshells was a response to the accumulation of 

 pesticides in the body tissues, originally acquired through contaminated prey. Along with 

 corrective management to enhance reproduction came the realization that raptors, being at the top 

 of the food web, could act as barometers of environmental health (Call 1978). Since then, raptor 

 populations have continued to receive special attention. 



Populations of several raptor species are still in decline, including some species breeding on 

 or near the Sioux District, Custer National Forest, in Montana and South Dakota (Dobkin 1994, 

 White 1994). The data on which population trends are based, however, are spotty and sometimes 

 give conflicting results, depending on the scale in space and time to which they are extrapolated. 

 For example, using a survey of the historical literature. White (1994) concluded that Swainson's 

 Hawk (Buteo swainsonii) is in significant decline in some western regions (especially California 

 and Oregon), whereas Dobkin (1994) used Breeding Bird Survey data to conclude that the 

 species is increasing in Montana and western North Dakota. 



To understand factors affecting populations of raptors on the local (Forest or District) scale 

 and to establish a baseline from which future monitoring and management efforts can be 

 implemented, it is necessary to first identify historical use of the area by raptors and then to 

 conduct thorough surveys of the populations currently present. This report presents previous 

 documentation and current evidence of habitat use and breeding activity on or near the Sioux 

 District, Custer National Forest, by five species of diurnal raptors: Swainson's Hawk, 

 Feraiginous Hawk {Buteo regalis) (C2 Federal Status, USFS Sensitive Status), Golden Eagle 

 {Aquila chrysaetos), Merlin {Falco columbarius), and Prairie Falcon {Falco mexicanus). Two 

 additional raptor species of special interest. Northern Goshawk {Accipter gentilis)(C2 Federal 

 Status) and Peregrine Falcon (Falco peregrinus) (Endangered Federal Status), have nested 

 previously on the Sioux District. The 1994 field survey focussed on cliff-associated species 

 (Golden Eagle, Prairie Falcon, Merlin); nesting Swainson's and Ferruginous hawks were not 

 surveyed. 



