Hematozoa of mallard ducks (Anas platyrhynchos) of the Pacific Flyway, Washington.

Blood smears from 837 mallard ducks (Anas platyrhynchos), collected during January and February from various locales in Washington during the period 1974-1977, were examined for hematozoa. Of these, 339 (40.5%) harbored blood parasites: Leucocytozoon simondi was the most common, occurring in 24.4% of the birds, followed by Haemoproteus nettionis (23.4%). Microfilariae were found in 14 birds (1.7%).