Riparian Species

Species of Deciduous Riparian Woodland

The Deciduous Riparian Woodland along the Muddy River and its tributaries on WSNA have an abundance of velvet ash (Fraxinus velutina), Fremont cottonwood (Populus fremontii), Goodding’s willow (Salix gooddingii), and California fan palm (Washingtonia filifera). The deciduous trees are especially important as nesting habitat for birds and as shade cover for native fish. The fan palms, while not desirable when they are impacting stream flow dynamics, do provide roosting habitat for the yellow bat and food for a variety of birds. Riparian woodlands have expanded along many irrigation ditches thereby extending the distribution of quality bird habitat. In many riparian areas, the trees alternate with or are replaced by the Riparian Shrubland Assemblage, forming an ecotone. Management of riparian woodland entails protecting existing quality habitat from fire, exotic plant invasion, and age-related decadence, as well as restoring riparian woodland along denuded stream reaches. Velvet ash and Goodding’s willow are particularly valuable riparian woodland species. Where recruitment of these species is not occurring naturally, site augmentation with propagated plants or transplants is recommended. The desired condition for this assemblage is a heterogeneous composition of age classes and tree densities throughout the riparian corridors. Fremont cottonwood provides the largest structural component in this assemblage and is an important habitat species. It readily pioneers disturbed riparian areas and will likely not require significant restoration attention. In established groves along irrigation ditches, the trees continue to persist because their roots have reached groundwater, but recruitment of new trees is limited because of discontinued irrigation. In such areas, managed restoration may be desirable. Because the California fan palm has invasive characteristics, develops undesirable fuel loads, and can negatively impact stream flow dynamics, it will not be purposefully planted as a component in riparian woodland restoration. In many woodland areas, the palms will be controlled in favor of more desirable native trees. Where fuel loads are not an issue, palms may be left intact. Where palm trees are removed, native tree species will be restored.

Species for Management Consideration

Southwestern willow flycatcher (Empidonax traillii extimus)
Western yellow-billed cuckoo (Coccyzus americanus occidentalis)
Townsend’s big-eared bat (Corynorhinus townsendii)
Western red bat (Lasiurus blossevillii)
Western yellow bat (Lasiurus xanthinus)
Fringed myotis (Myotis thysanodes)

Riparian Species

Southwestern willow flycatcher
(Empidonax traillii extimus)
The southwestern willow flycatcher is a small, insect-eating bird that has been protected as an endangered species by the US Fish and Wildlife Service since 1995. There are estimated to be only 900 – 1,000 breeding pairs of the southwestern willow flycatcher. Southwestern willow flycatchers breed in sites that have very dense tree cover usually close to water and over saturated soil.Resident southwestern willow flycatchers were noted on the Warm Springs Natural Area in 2004, 2005, 2007, 2008, 2009, and 2010. In 2008, nine southwestern willow flycatchers were located on WSNA north of the Apcar Stream (Braden et al. 2009). In 2009, four birds were found in dense patches of trees north of the Muddy River (Klinger & Conrad 2010). Of the four birds detected, two were a pair that fledged three young (McLeod et al. 2010).

Western yellow-billed cuckoo
(Coccyzus americanus occidentalis)
The Western yellow-billed cuckoo is a medium-sized, slender and inconspicuous bird that forages in dense, leafy trees and eats large insects such as grasshoppers and caterpillars. The Nevada Department of Wildlife has identified cuckoos in a few areas around the state in small numbers. These birds are nomadic and numbers fluctuate greatly from year to year. A significant portion of the cuckoos found in Nevada in the early 2000s were at the Warm Springs Natural Area but more recent surveys have only detected one bird each year from 2003 to 2006, zero in 2007, and three in 2008. Two detections were made in 2009 (Bruce Lund, personal communication, 2009). These birds have been observed in the large woodland north of the main stem of the Muddy River (Braden et al. 2009), but cuckoos can be found throughout the WSNA in appropriate habitats.

Summer tanager
(Piranga rubra)
The summer tanager, a Clark County Multiple Species Habitat Conservation Plan Covered Species, is a medium-sized bird with a stout bill. Males are a brilliant red color and females are a buffy orange color. Males have small crests. Summer tanagers feed on bees and wasps that they catch in the air. They are confirmed breeders on the Warm Springs Natural Area according to Great Basin Bird Observatory (Appendix 4). Management for the summer tanager is similar to management for the southwestern willow flycatcher andincludes preservation and establishment of dense riparian vegetation.

Western yellow bat
(Lasiurus xanthinus)
The Western yellow bat has been recorded roosting in the palm trees (Washingtonia filifera) of the Warm Springs Natural Area. This is the only population of yellow bats that has been located in Nevada, and this population is disjunct and more northerly than other populations of yellow bats (O’Farrell et al. 2004).

Riparian Woodland Bat Species

Western yellow bat (Lasiurus xanthinus)
Townsend’s big-eared bat (Corynorhinus townsendii)
Western red bat (Lasiurus blossevillii)
Fringed myotis (Myotis thysanodes)

Riparian Shrubland

The Riparian Shrubland at WSNA occurs along sections of the South Fork and Muddy River as well as along some irrigation ditches. Shrubs including Emory’s baccharis (Baccharis emoryi), arrowweed (Pluchea sericea), coyote willow (Salix exigua) and other riparian non-obligates such as quailbush (Atriplex lentiformis) commonly occur in this assemblage. This riparian shrubland provides valuable habitat for birds, small mammals, and terrestrial invertebrates.

MacNeill sooty wing skipper
(Hesperopsis gracielae) Quailbush is a known host plant for the MacNeill sooty wing skipper. Larvae of this butterfly feed on the leaves whereas the adults forage for nectar on flowering plants. Quailbush occurs abundantly at WSNA and is not in danger of diminishing. The MacNeill sooty wing skipper is considered common to abundant in Moapa Valley having been collected from Bowman Reservoir and Hidden Valley (Austin & Austin
1980). Hidden Valley is approximately five miles south of the WSNA and no fragmented host plant populations occur between recorded collections and the WSNA property. Adults have been recorded nectaring on tamarisk, salt heliotrope (Heliotropium curassavicum), and alfalfa (Medicago sativa) (Austin & Austin 1980). However, Nelson (2009) did not record the MacNeill sooty-wing skipper at the WSNA during limited sampling in April and July 2009.

MacNeill sooty wing skipper (Hesperopsis gracielae)

Riparian Marsh Meadows
Marshes and seeps provide essential habitat for amphibians, birds, invertebrates, and small mammals. Because wetland habitat is so productive, it provides the food base to support higher trophic species such as predators. Due to its rarity and resource-rich quality within an otherwise resource-scarce Mojave Desert ecosystem, riparian marshes and seeps attract and harbor an abundance of wildlife.

Marshland on the Warm Springs Natural Area is primarily derived from spring outflow that may be either partially ponded or terminates in wet meadows. The amount of water varies seasonally with the greatest standing water most abundant during the winter months when the groundwater is particularly close to the surface. In some areas, riparian meadow vegetation can be found where surface water is entirely absent. Vegetation in such areas is supported by the high water table in the winter months. Riparian meadows form an important feeding ground for many of the bird species found on the natural area. Mowing in combination with periodic prescribed fire is useful to maintain the health and productivity of riparian meadows. The few marshes found on the Natural Area are largely overgrown with cattails and would benefit from the management practices that expose surface water for waterfowl and other wildlife.

Introduction of the Relict leopard frog
The relict leopard frog (Lithobates onca) historically occurred in springs near the Colorado, Virgin, and Muddy Rivers including the springs at the headwaters of the Warm Springs Natural Area (Bradford et al. 2004). By 1950, this frog was believed to be extinct. However, in 1991 relict leopard frogs were rediscovered in several springs near Littlefield Arizona, near Lake Mead, and below Hoover dam. Conservation efforts include monitoring existing populations, enhancing spring habitats, captive rearing, and translocating frogs into historic and new locations. Because Warm Springs Area is within the historic range of the relict leopard frog, frogs were relocated to adjacent lands owned by Clark County in 2010. Releasing relict leopard frogs on the Warm Springs Natural Area may be part of recovery efforts for this species.