ARCHIVED REPORTS_1993_1 - Laserfiche WebLink

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1 Tricolored blackbirds nest in dense wetland vegetation and blackberry thickets and forage in grasslands and agricultural fields as far as 4 miles from a nesting colony (Beedy et al. 1991). Tricolored blackbirds have declined throughout their range due to loss of wetland breeding habitat, nest disturbance, aerial spraying of pesticides and herbicides, and mortality from poisoned grain (Terres 1987, Beedy et al. 1991). Status in the Project Area. Tricolored blackbirds were not observed during field surveys, nor is there suitable nesting habitat at the project site. In 1993, tricolored blackbirds nested approximately 10 miles east of the project site on Durham Ferry Road (Yee pens. comm.). Tricolored blackbirds could occasionally forage at the project site in winter but are not expected to occur during the breeding season because of the lack of breeding habitat within suitable foraging distance of the project site. Mountain Plover Background. A major portion of the wintering population of mountain plovers is found in the Central Valley (Leachman pers. comm.). The plover occurs regularly along the west side of the Central Valley from Yolo and Colusa Counties southward and in the foothills west of the San Joaquin Valley (McCaskie et al. 1979). The plover forages and roosts in plains of short grass and low, rolling hills with sparse herbaceous vegetation; freshly disked agricultural fields; and sprouting grainfields (Grinnell and Miller 1944, Leachman pers. comm.). The number and size of plover flocks has declined in recent decades (Leachman pers. comm.). Several factors have contributed to the decline of mountain plover populations, including the loss of breeding and wintering grassland habitat converted to agricultural fields and residential and commercial developments (Leachman pers. comm.). Status in the Project Area and Vicinity. Mountain plovers were not observed during Jones & Stokes Associates' February field survey. There are no known wintering use areas in San Joaquin County; however, many wintering plovers are frequently observed near Clifton Court Forebay approximately 10 miles northwest of the project site (Yee pers. comm.). Mountain plovers could be expected to occur infrequently and in small numbers in annual grasslands at the project site. IMPACTS AND MITIGATION MEASURES Criteria for Determining Significance Botanical and wildlife impacts were considered less than significant if: species are widespread locally and statewide; special -status species are unlikely to be present; or habitats are dominated by introduced species, do not support other significant attributes, and have low habitat value to wildlife. Impacts were considered significant if they cause: adverse effects on substantial areas of significant natural communities, such as wetlands or vernal pools; • direct mortality, temporary or permanent habitat loss, or lowered reproductive success for individuals of plant or wildlife species that are state or federally listed or proposed for listing; or ER -93-1 41 - (9-27-93)