N. OSPREY 



1) Introduction 



No records were located indicating the extent of the osprey 

 population along the Kootenai River prior to construction of the 

 Lifcfciy Dam project; however, it was assumed an unknown number of 

 osprey were present. 



2) Seasonal Habitat Preference 



Osprey require a combinaticn of suitable nesting sites - on 

 islands, or within upland forests adjacent to lakes and reservoirs - 

 and prey (fish) availability. Ospreys have been documented nesting 

 along both rivers and lakes in Montana (MacCarter and MacCarter 

 1979, Swenson 1981, Grover 1983). Preferred nest sites are typi- 

 cally large deciduous and coniferous snags, live coniferous trees, 

 or powerpoles (MacCarter and MacCarter 1979). 



3) Population Status 



Surveys conducted by the U.S. Forest Service within the Fisher 

 River Ranger District provided limited data on the osprey popu- 

 lation along the portion of Lake Koocanusa within the district 

 (U.S. Dep. Agric. unpubl. files). Since 1974, a maximum of 4 

 active osprey nets have been known to exist within the district in 

 during a nesting season. A complete survey of the reservoir has 

 not been completed; however. Brown (1983, pers. commun.) indicated, 

 during aerial censuses of big game populations, a large number of 

 osprey nests were observed and the estimates of osprey use of the 

 area by the U.S. Forest Service were probably low. Nest sites 

 observed during the surveys were not recorded so a density estimate 

 could not be developed. 



4) Assessment of Impacts 



Increased use of reservoirs over pre-impoundment rivers by 

 nesting ospreys has been documented elsewhere in Montana (Swenson 

 1981, Grover 1983). Grover (1983) reported 1.0 occupied nest per 

 1.15 miles along Canyon Ferry Reservoir compared to 1.0 nest per 

 20.7 miles along the free-flowing river. It was assumed, if a 

 complete osprey nest survey within the reservoir area and a portion 

 of the free-flowing Kootenai River was conducted, an increase in 

 the osprey population within the impact area since the completion 

 of the Libby Dam project would probably be indicated. 



5) Estimated Losses/Gains Due to the Project 



- Quantitative loss/gain estimate - none could be developed. 



- Qualitative loss/gain estimate - low positive. 



68 



