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Bird Monitoring Program - Bostick Bird Census
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| Cinnamon Teal |
Introduction
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 in their life cycle. Studies
conducted in the early 1970s identified more than 200 species
of birds along the Wash. However, the past 30 years have brought
dramatic changes to the Wash. Erosion has reduced the wetlands
that once covered over 2,000 acres to less than 200 and riparian
areas have become infested with the exotic invasive
salt cedar. 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.
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| RRAS volunteers |
Consequently, in November 2000, the LVWCC began
a bird census with volunteers from the Red Rock Audubon Society
to collect baseline data to monitor the effects of Wash improvements
on the bird population. The goals of the census are to inventory
the bird species found in the Wash, record the use of the Wash
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.
Method
To conduct the census, two to three volunteer RRAS birders walk a pre-established path on the study site for approximately 2-3 hours, identifying all birds seen and/or heard. Project Team staff accompany the birders and record 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 reevaluated, and it was deemed appropriate to continue the census at one location and reduce the census frequency 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. Since the weir was completed in August 2003, censuses have been conducted on a quarterly to bi-monthly basis.
Results through 2005
The bird census completed
its fifth study year on October 17, 2005. A total of 133 species
from 44 families were recorded during this period. Resident species
commonly seen on the census include 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 also made appearances during the
five-year period, including palm warbler, wood duck, golden-crowned
kinglet, and northern saw-whet owl.
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| Long-billed Dowitcher |
Changes in species richness related to the construction of Bostick
Weir were recorded over the five-year study period. 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.
Species identified per census visit decreased from an average
of 29 species over the same period during the previous year
to an average of 20 species. After the weir was complete and
the impoundment (a large pond) behind it was created, species
identified per census rose again. An average of 32 species
per visit have been identified since. Waterbirds
appeared that had not been observed at the site previously,
such as western, Clark's, and eared grebes. Winter waterfowl
numbers also increased significantly, with dozens of gadwall,
mallard, and other species counted in the weir’s impoundment
and on the weir itself during the winter months. Raptors have
also taken advantage of the pond. Osprey, northern harrier,
red-tailed hawk, and prairie and peregrine falcon have been
observed hunting for their next meal in the impoundment.
The LVWCC extends it thanks to the dedicated RRAS volunteers who have collectively contributed more than 500 hours to this project.
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