Riparian habitat typically has trees, shrubs, and other streamside vegetation found along intermittent and perennial waterways. This combination of plants is crucial to the survival of a host of wildlife species on the Refuge. The tall grasses provide excellent nesting habitat for the numerous waterfowl species on the Refuge. The tall cottonwoods provide nesting and roosting sites for a variety of raptors, including large concentrations of wintering bald eagles.
Historically, the Rio Grande would have flooded frequently, regenerating willows and cottonwoods. However, the Valley’s riparian habitat has been reduced by the diversion of surface water and depletions from ground water use. This habitat also suffers from excessive grazing and browsing, which further limits growth of willows and narrowleaf cottonwood trees.
The most critical part of the riparian zone along the Rio Grande River is the low growing dense stands of willow. Shrubs that contribute to the diversity of riparian habitat include redosier dogwood and greasewood. These areas provide important stopover habitat for migratory songbirds, as well as nesting habitat for birds such as Lewis’ woodpecker, willow flycatcher, and possibly yellow-billed cuckoo. The endangered southwestern willow flycatcher nests in the dense willows and feeds on the abundant insects found along the river.
Numerous year-round residents, including elk and mule deer, use the riparian corridor throughout the year. Dense stands of willow also provide secure fawning areas for the deer, as well as excellent thermal cover during the winter months. The shade and streambank stabilization provided by riparian vegetation is important in keeping temperature and water quality in streams and rivers for native fish such as the Rio Grande cutthroat trout, Rio Grande chub, and Rio Grande sucker.
Upland habitat is the most common natural vegetation on the San Luis Valley floor. Many of the plants are drought resistant and tolerant of high soil salinity such as black greasewood and rabbit brush. The uplands provide important habitat for declining bird species such as the sage thrasher and Brewer’s sparrow along with bull or gopher snakes, black- and white-tailed jackrabbits and desert cottontail rabbits.