Hematologic parameters were studied in giant Canada geese (Branta canadensis maxima), mallard ducks (Anas platyrhynchos platyrhynchos) and various species of diving ducks at seasonal intervals throughout the year. Highest values for packed cell volume, hemoglobin content and erythrocyte counts were found in the winter and pre-nesting periods. Mean corpuscular volume and mean corpuscular hemoglobin varied inversely with these values.