4) Assessment of IiT (pacts 



Breeding habitat for a variety of waterfowl species was lost 

 when the Libby Dam project was constructed. Nesting habitat for 

 cavity and upland nesting species was provided by: the 23 vegetated 

 islands and a portion of the 24 non-vegetated islands; deciduous, 

 Cottonwood and mixed deciduous/coniferous riparian areas; and sub- 

 irrigated grasslands. A total of 52.5 miles of riverine habitat 

 (3,285 acres), 48.8 miles of tributary habitat and 29 acres of 

 standing water were replaced by a large body of water. Lake Kooca- 

 nusa contains two islands with coniferous habitat which are not 

 conducive to waterfowl nesting or feeding. Though numerous snags 

 are available for nesting waterfowl, loss of brooding habitats had 

 the greatest impact on local waterfowl populations. Most of the 

 species assumed to have nested in the valley are dependent on an 

 inter spers ion of grassy or emergent cover and open water for broods 

 (Bellrose 1976). These areas provide a combination of escape cover 

 and macroinvertebrate prey (Sugden 1973) essential to brood surv- 

 ival. Examples of such habitats present prior to the formation of 

 the reservoir were sloughs, marshes and backwater areas along the 

 two rivers and their tributaries. Since many species initiate 

 nesting during low early spring flows, later water releases from 

 Libby Dam may also flood many of the waterfowl nests on the down- 

 stream islands. In addition, the sub-irrigated grasslands inun- 

 dated by the project providec3 brood rearing areas for the Canada 

 goose population similar to those des-cribed by Ball et al (1981). 

 Harlequin duck brood habitat, charac-terized by swift water habi- 

 tats of interspersed pools and riffles (Kuchel 1977), and known to 

 be present along the existing free-flowing river (Joslin 1978), was 

 also inundated by the project. 



Shoreline habitats along lake Koocanusa are currently unsuit- 

 able as waterfowl brood-rearing areas. Fluctuating water levels 

 have led to extensive mudflat areas lacking the emergent or herb- 

 aceous vegetation necessary for food and cover, prerequisites for 

 brood survival. Changes in macroinvertebrate species composition 

 due to the impoundment of the river (McMullin 1979, Bonde and Bush 

 1982) may also have affected food resources available to broods. 



Creation of a large reservoir increased the open water areas 

 available as resting habitat for migratory flocks of waterfowl. 

 Lack of established stands of aquatic vegetation in the littoral 

 zone, caused by fluctuating water levels, limits food availability 

 and lowers the value of the reservoir to migratory waterfowl when 

 conpared to natural lakes in the region. 



Winter habitat for waterfowl was lost when the primarily open- 

 water river habitats were replaced by a reservoir which completely 

 or partially freezes over each winter. It was assumed the winter 

 'nabitat along the Kootenai River was suboptinal. 



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