East Bay Municipal Utility District conducted a survey of falcons, kites, hawks and owls in the lower Mokelumne River watershed in central California from April 1998 through April 2001 to determine species composition, relative abundance and habitat use. The survey consisted of day and night surveys of the lower Mokelumne River by boat and roadside surveys of the watershed by automobile. The 781 person-hours of surveying yielded 2,172 observations of 16 species. Red-tailed hawk, Buteo jamaicensis, American kestrel, Falco sparverius, Swainson’s hawk, Buteo swainsoni, white-tailed kite, Elanus leucurus, red-shouldered hawk, Buteo lineatus, northern harrier, Circus cyaneus, and osprey, Pandion halieatus, were the most commonly observed species. For these species combined, habitat selection indices were higher in Valley Oak Woodland than all other habitats, followed by Irrigated Hayfield/Pasture, Valley Foothill Riparian and Annual Grassland. All other habitats had combined selection indices of less than one. The combined distribution of these species among the watershed habitats was significantly heterogeneous. Distribution of each of the seven most common species among the watershed habitats was also significantly heterogeneous. Although habitat selection changed by season and year, the combined observations indicated that all species observed preferred Valley Oak Woodland except osprey, which preferred Valley Foothill Riparian.
