The recent rash of bird deaths in Richardson Bay may be avian cholera. The first necrospy done on three birds showed that one bird died of this highly contagious bacteria. The disease is commonly transmitted through contact with secretions or feces of infected birds or the ingestion of food or water containing the bacteria.
According to the California Fish and Games website: “Avian cholera (not related to human cholera) is a common disease of North American waterfowl and results from infection with the bacterium Pasturella multocida. It spreads rapidly from bird-to-bird and can kill thousands of birds in a single incident. A bird infected with avian cholera dies quickly. Avian cholera die-offs in waterfowl commonly occur during the winter months in California, especially during cold spells and fog.”
At least 235 birds were picked up dead over the past two weeks. The spike was blamed on two recent sewage spills into the bay. At least 5 million gallons of partially treated human waste was dumped from the Marin County area. Scientists believe that the spill may have contributed to the rise of avian cholera. More tests on some of the other dead birds will help researchers determine the true cause.
See the San Francisco Chronicle story: Cholera killed bird found in Richardson Bay