SUMMARY OF HABITAT RELATIONS 



The Kootenai FaPs area is a complex mosaic of many different 

 habitats, each harboring its own assemblag'^ of animals. Figure 9 

 shows the pattern of distribution of selected vertebrates among habitats 

 of three generalized cross-sections of the Kootenai River Valley (at the 

 Falls, at the gorge below the Falls, and upstream from the Falls). 

 Typical vertebrate species associated with each of the habitat categories 

 listed in Table 1 are discussed below. 



W ater Habitats 



Rapids . The only species which was observed to use rapids extensively 

 was the dipper. Aquatic insects associated with rapids provided an 

 important food source for the dipper, and wintering dippers concentrated 

 at major rapids. 



Fall s. Kootenai Falls is the only remaining unimpounded falls of a 

 major river in Montana, and as such provides a unique habitat. The 

 Falls of the Yaak River, located north of Troy, is smaller and of lower 

 gradient than Kootenai Falls and does not provide a comparable habitat. 

 Kootenai Falls actually consists of several very different habitats, 

 which receive different levels of use by different wildlife species. 

 The thalweg (deepest part) of the river channel is located near the 

 north bank of the river at the Falls, and -- at all flows -- most of the 

 water volume descends the Falls through this channel. Water velocity is 

 high in this constricted channel, and flow is very turbulent. A large 

 island separates the main flow into north and south channels just below 

 the head of the Falls. The only species observed to use the crashing, 

 turbeulent water and spray of the main channels was the dipper. The 

 head of the Falls and the minor channels below are a highly variable 

 environment, depending on the pattern of discharge from Libby Dam. A 

 series of relatively flat rock benches occur at the head of the Falls, 

 south of the main channel and form a stairstep pattern leading to the 

 sheer rock dropoffs of the Falls itself. These rock benches are densely 

 covered with periphyton the river's southern bank. At low flows of 112 

 to 168 cms (4,000 - 6,000 cfs), most of this rock is dry and exposed or 

 supports a gentle trickle of water from the relatively calm pool upstream; 

 relatively little water descends over the Falls here, and the minor 

 channels downstream are essentially calm pools. At high flows of 168 cms 

 (6,000 cfs) and higher, a much larger volume of water cascades in a 

 turbulent manner over the rock benches and the edge of the Falls, and 

 the minor channels are turbulent as well, producing considerable spray 

 and white water. At nearly all discharges, water flow across the benches 

 between "stairsteps" is laminar rather than turbulent somewhere near the 

 center of the Falls, and provides preferred feeding habitat for the 

 harlequin ducks, the most distinctive and characteristic species of the 

 Falls habitat. Harlequins are presumably feeding on diptera larvae 

 (probably Simuliidae) in this swift water. Dippers feed in the same 

 general area, but competition with the harlequins for food resources is 

 avoided, as dippers feed in shallower water, closer to the rocks, and 



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