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Bird Census

The Las Vegas Wash offers a refuge of riparian and wetland habitat in the arid Mojave Desert. These habitat types are critical to many bird species at some point or another in their life cycle.

Studies conducted in the early 1970s identified more than 200 species of birds along the Wash. But in the decades since, erosion caused dramatic changes to the Wash. Wetlands that once covered more than 2,000 acres were reduced to less than 200, and riparian areas became infested with the invasive salt cedar (also known as tamarisk).

The Las Vegas Wash Coordination Committee's (LVWCC) efforts to stabilize the Wash channel, clear invasive plant species, and revegetate hundreds of acres with native wetland, riparian, and upland plants should have a positive impact on the avian community in the Wash.

From November 2000 through October 2006, the LVWCC conducted a bird census with volunteers from the Red Rock Audubon Society (RRAS) to collect baseline data to monitor the effects of Wash improvements on the bird population. The goals of the census were to inventory the bird species found in the Wash, record the use of the area by birds prior to, during and after weir construction, and compare bird species present in revegetated habitat with those present before the area was revegetated.

Redwinged Blackbird. Photo by: Dick Barrett.
Redwinged Blackbird Photo by: Dick Barrett

To conduct the census, RRAS birders walked through the site on a pre-established path for approximately two to three hours, identifying all birds seen and/or heard. Wash Team staff accompanied the birders and recorded their observations. For the first year, the bird census was conducted biweekly at two sites, the future site of the Bostick Weir and the future site of the Sunrise Mountain Outfall Weir. At the end of the first year, the census was discontinued at the Sunrise site and census frequency was reduced to a monthly basis. The decision was made to continue the census at the Bostick site because weir construction had been postponed until September 2002, allowing two years of pre-construction data to be collected. Following the weir's completion in August 2003, censuses were conducted several times a year.

A total of 140 species from 46 families were recorded during the six-year study period. Resident species commonly seen on the census included double-crested cormorant, great blue heron, american coot, black phoebe, Abert's towhee, and song sparrow. Other birds, such as the marsh wren, black-tailed gnatcatcher, and verdin were infrequently seen, but often heard. Rare species including palm warbler, wood duck, golden-crowned kinglet, and northern saw-whet owl also made appearances.

Changes in species richness related to the construction of Bostick Weir were recorded over the course of the study. Construction of the weir began in September 2002 and was completed in July 2003. By the time the weir was finished, the census site had changed from a narrow, tamarisk-bordered channel to a bare expanse of earth undergoing heavy construction and finally to a large, shallow open body of water. When construction activity was at its peak, species richness decreased. Disregarding flyovers (birds that flew over but did not land in the site), species identified per census visit decreased from an average of approximately 21 species over the same period during the previous year to an average of approximately 17 species.

After the weir was complete and the impoundment (a large pond) behind it was created, species identified per census rose again and an average of approximately 29 species were identified per visit. Waterbirds appeared that had not been observed at the site previously, such as western, Clark's, and eared grebes. The number of winter waterfowl and other waterbirds detected also increased significantly, with dozens of gadwall, mallard, American coot, and other species counted in the weir’s impoundment and on the weir itself during the winter months. Raptors also took advantage of the pond. Osprey, northern harrier, red-tailed hawk, and prairie and peregrine falcon were observed hunting for their next meal in the impoundment.

The LVWCC extends it thanks to the dedicated RRAS volunteers who collectively contributed more than 500 hours to this project.

Reports for the Las Vegas Wash Bird Census can be found in the Wildlife section of the Document Library.

Las Vegas Wash Project Coordination Team • 100 City Parkway, Suite 700 • Las Vegas, NV 89106 • (702) 822-3300