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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