Northern Prairie Wildlife Research Center
Assessments of Habitat and Predator Management for Upland
Nesting Gamebirds Near High Desert Marshes in California
M. ROBERT McLANDRESS AND DAVID S. ZEZULAK
California Waterfowl Association, 3840 Rosin Court, Suite 200,
Sacramento, CA 95834
Upland fields where ducks nested near the Honey Lake and Ash Creek State Wildlife
Areas in northeastern California were examined annually from 1987 to 1989. Perennial
grasses provided attractive cover for breeding ducks, but nest success was low
in old, established fields (less than 10%, Mayfield method). Intensive predator
removal in and around these fields showed dramatically increased nest success.
Annual grasses were not tall enough in spring to provide attractive early duck
nesting cover in northern California, but late-season nest success of ducks
that used these fields was high. Established perennial grass habitats provided
stable and predictable environments relative to annual grass fields. Predators
probably concentrate their activities in perennial grass fields because they
provide food and shelter at times of the year when few alternative resources
are available. Duck eggs are a particularly important food item because they
are available early in spring when other foods are scarce.
Investigations of uplands in the Klamath Basin on Tule Lake NWR for nesting
ducks in 1988 and nesting pheasants in 1989 were also conducted. The majority
of available nesting cover consisted of alfalfa, tule marsh, and unfarmed
strip habitat adjacent to irrigation canals in this heavily farmed wildlife
refuge. Over the past 15 years, crested wheatgrass (Agropyron cristatum)
has been planted to control and replace natural weed guilds in nearly a third
of the strip habitats. These wheatgrass strips provide poor cover and are
unattractive to ground-nesting birds. In contrast, strip habitat composed
of numerous weed species was heavily used for nesting. Nest densities in alfalfa
and tule marsh habitats were high, but success was low. Thus, residual vegetation
in the more complex perennial weed habitat provided the most productive early-season
nesting habitat on the wildlife refuge.
Establishment of perennial grasses for ground-nesting birds in northeastern
California is not desirable in some situations. Moreover, where dense stands
presently exist, predator control and/or periodic habitat perturbations are
required. These practices maintain wheatgrass as an attractive nesting cover,
disrupting predator populations and their hunting patterns.
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