The Northern Rockies and Southern Rockies / Colorado Plateau Regions (Region 9*) include several ecosystems ranging from alpine tundra to sagebrush flats. Much of the diversity of the RCP is attributable to its topographic relief, which ranges from 1,000 to 4,300 m. Elevation changes result in ecosystem regions or "life zones" characterized by differences in precipitation, humidity, temperature, growing season, wind, exposure, and soil conditions. The four life zones recognized in the Rocky Mountains—Lower Montane, Upper Montane, Subalpine and Alpine—possess unique flora and fauna. The Alpine has few woody species (mostly willows), but contains abundant grasses and forbs characteristic of vegetation at much higher latitudes. Subalpine areas contain Englemann spruce and subalpine fir. Upper Montane habitats are somewhat drier, and are dominated by blue spruce, Douglas fir and several other coniferous species. Lodgepole pine and aspen are the most common species in Lower Montane areas. Depending on the latitude, sagebrush, rabbitbrush and black greasewood are the dominant species in the intermountain basins.
Waterfowl habitats in the RCP have several attributes that set them apart from their prairie counterparts. First, montane wetland communities are relatively intact compared with the widespread wetland degradation typical of the northern Great Plains. This more nearly pristine condition reflects the rugged topography and generally poor soils of the region, which favors ranching, timber harvest, and mining over farming. Additionally, many areas are afforded some degree of natural resource protection by virtue of their inclusion in the National Forest System or as BLM holdings. The most secure areas are lands set aside as wilderness areas or research natural areas. Second, except where locally affected by mining operations and ski areas, for example, upland plant communities are still dominated by native plant species. Third, although the magnitude of the snowpack and rainfall varies annually, precipitation is almost always sufficient to provide adequate water for ducks and geese. Thus, waterfowl habitats in the RCP is relatively stable compared with those in the prairies.
The geology and topography of the RCP create a greater diversity of wetland types than are found in the prairies. Annual primary production decreases with elevation, so wetland succession proceeds much more slowly in montane wetlands than in low elevation ponds. Most high elevation wetlands are slightly acidic to circumneutral and contain relatively small amounts of dissolved nutrients compared to a typical prairie wetland. Accordingly, only some wetland communities—intermountain basin wetlands, beaver ponds, glacial ponds, and riparian corridors—are heavily used by waterfowl. Understanding the nature of these wetland communities is important to the success of any waterfowl management initiative in the RCP.
The intermountain basins or "parks" of the RCP contain the most important waterfowl habitats in the region. The flat or rolling topography typical of mountain parks, which originated from tectonic and volcanic events during the formation of mountain ranges, is underlain by deep layers of alluvial material eroded from the surrounding mountains. Although relatively few in number—33 parks have been identified in the RCP—intermountain basins are often several hundred square kilometers in size. Many parks are considered cool deserts because of the low precipitation created by the rain shadow of surrounding mountains. The average frost-free period may be <2 months. Despite low seasonal temperatures, ratios of precipitation to evaporation are usually <1, causing the development of pedocal soils. Where alkali deposits occur in poorly drained areas, salt-tolerant plants such as black greasewood and saltgrasses are common. Less saline areas typically contain wheatgrasses, bluegrasses, sedges and rushes, or shrubs such as sagebrush and rabbitbrush. Ranching and haying are the most common land use, but some grain crops and cold-weather vegetables are grown in more temperate parks. Many intermountain basins contain relatively few wet areas, but some—such as the 13,000 km2 San Luis Valley in south-central Colorado—possess abundant wetlands. Wetlands are formed by spring runoff, which creates shallow water areas and recharges the persistently high water tables, and by artesian flows and impoundments. Lakes and reservoirs provide important migratory staging and molting habitats, and lake margins attract breeding waterfowl. High densities of aquatic invertebrates such as freshwater shrimp and the larvae of dragonflies, midges, flies, and mosquitoes abound in these wetlands, providing abundant food for waterfowl.
*Region 9 - NABCI Bird Conservation Regions 10 & 16. Region 10 in Canada is covered in above section.