High Elevation Riparian
Description and Ecology:
A) Subalpine Riparian Shrubland
These ecosystems may be extensive in broad, glacial valleys, along stream systems and other
wetlands from 2450 to 3650 m (8,000-12,000 ft) elevation. They have relatively low plant
diversity--comprised mostly of willows, shrubby cinquefoil, and bog birch. The low plant
diversity along with the short growing season usually results in low avian species diversity as well.
However the dense willow thickets provide many protected nest sites and an abundance of
insects. This results in a high density of nesting birds in a given area. Species most commonly
found in these areas are Broad-tailed Hummingbird, Dusky Flycatcher, Yellow Warbler,
MacGillivray's Warbler, Wilson's Warbler, Lincoln's Sparrow, Song Sparrow, White-crowned
Sparrow, and Fox Sparrow.
B) Foothills Riparian Forest
Foothills riparian forests are distributed along stream systems in the foothills, lower mountains
and mountain parks from 1700 to 3050 m (5,500-10,000 ft) elevation. In some areas the riparian
forest is dominated by a deciduous component, especially narrowleaf cottonwood, a variety of
willow species, box elder, mountain alder and river birch. In other areas Colorado blue spruce
and other coniferous trees dominate, and conifers often form a mixture with cottonwoods. The
understory of these systems is typically rich, with a wide variety of shrubs and herbaceous plants.
The Colorado Breeding Bird Atlas (Kingery 1998) reported that foothills riparian forests
dominated by deciduous trees comprised nearly 85% of all foothills riparian forests, while conifer-dominated systems comprised just over 15%. These two systems also exhibited somewhat
different avian communities. In deciduous systems, Yellow Warbler was the species most
frequently detected, followed by American Robin, Northern Flicker, House Wren, Warbling
Vireo, Song Sparrow, Western Wood-Pewee, and Broad-tailed Hummingbird. In coniferous
systems, Cordilleran Flycatcher was the most frequently detected species, followed by Broad-tailed Hummingbird, Ruby-crowned Kinglet, American Robin, Golden-crowned Kinglet,
Swainson's Thrush, Mountain Chickadee, Yellow-rumped Warbler, and Western Tanager.
Importance and Conservation Status: Riparian ecosystems are highly important areas for both
humans and wildlife. They are convenient locations for roads and trails, mining activities, and
dams and water diversions. They are also productive areas for domestic livestock grazing.
Riparian areas are under constant assault from these and other activities which cause habitat loss
and degradation, disturbance, dewatering, and pollution (Melton et al. 1984, Wozniak 1995).
Riparian areas represent a transition zone between the aquatic ecosystem and the drier uplands.
The riparian zones are well defined, unique, and highly productive areas which are sensitive to
disturbance (Melton et al. 1984). Riparian systems occupy no more than 3% of the Colorado
landscape (Kingery 1998); however, 75% of the bird species in the West use riparian areas during
some part of their life cycle (Howe 1996).
Perhaps one of the most dramatic and widespread impacts on riparian areas in the West comes
from domestic livestock use. Domestic livestock are disproportionately attracted to riparian areas
during the summer months when uplands are hot and upland vegetation is drying out. The high
moisture and nutrient content of riparian forbs and shrubs during the summer months are
irresistible to domestic livestock. As a result of grazing and trampling, many riparian areas are
devoid of understory vegetation at a time when it is most critical as cover and food source for
avian species (Krueper 1995).
Much of the high elevation riparian habitat in Colorado is controlled by federal land managers.
Better control of domestic livestock use on these Federal lands could make a substantial
difference in the health of the riparian communities in the state. In many cases, total removal of
domestic livestock is not needed to make a substantial improvement in riparian vegetation
condition; simply a change in the season of use and or change in the length of use of the riparian
pastures could make a substantial difference (Myers 1991).
Priority Species Accounts: Four species are identified as high priority in high-elevation riparian habitats
in Physiographic Area 62: Cordilleran Flycatcher, American Dipper, MacGillivray's Warbler, and Wilson's Warbler.