The 1970–71 avian cholera epornitic was the third highest in waterfowl mortalities during the 22 annual California recurrences for which we have records. The most serious aspect of this outbreak was its impact on species which, although not classified as rare and endangered, nonetheless are in low numbers. For example, 7.3 percent of the Ross goose (Chen rossii), and 3.9 percent of the whistling swan (Olor columbianus) populations wintering in California died of avian cholera as well as ten sandhill cranes (Grus canadensis) and one bald eagle (Haliaeetus leucocephalus). A possible cause of the large losses of waterfowl was a late winter drought with resultant local high concentrations of birds and heavy contamination of the water.