The term 'small aquatic bird' can be summarized by the crossword solution 'Gallinule, ' which is a nine-letter word. Gallinules are small, freshwater birds that are related to coots and moorhens. They have short, rounded wings and long toes that allow them to swim and walk on floating vegetation. They are found in wetlands throughout the world, and they feed on aquatic plants, insects, and small fish.