The pisciverous western grebe (Aechmophorus occidentalis) nests in the tule marshes bordering several freshwater lakes in California. Historically, plume hunting and the draining of the vast marshes of the Central Valley caused drastic declines in western grebe populations during the 19th century. Recent hydrologic and shoreline development of inland lakes has eliminated or drastically reduced the amount of remaining breeding habitat. The current breeding status of western grebes on the Salton Sea, Sacramento Wildlife Refuge, Topaz Lake, Eagle Lake, Clear Lake, Lake Earl, and Tule Lake is reviewed. Clear Lake, Lake County, provides a unique example of direct and indirect human destruction of breeding western grebe colonies. Environmental pressures at Clear Lake are amplified by three categories of human disturbance: pesticide treatment of the lake (ODD and parathion), reduction in food supply, and loss of breeding habitat. Western grebe colonies on lakes near human population centers suffer the most amount of human disturbance and hence reproductive failure. The number of nesting western grebes in California is dangerously low; furthermore, continued declines are projected unless rigorous land use planning and management efforts are initiated.
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