Blood smears were procured from 1,011 geese and ducks of 19 species from various locations in California. Parasites were found in 28 individuals. The parasites observed included Haemoproteus hermani, Leucocytozoon simondi, microfilaria, Plasmodium relictum (=P. biziurae), and Plasmodium sp. with elongate gametocytes. This is the first report of a natural infection with a Plasmodium in North American wild ducks.