Went to Botanic Gardens during Lunar New Year. Saw some Lesser Whistling-Ducks and Radjah Shelducks. It was the first time that I was observing their eyes at close range and had some interesting findings.
Lesser Whistling-Ducks tend to shut their eyes when preening their feathers, while only saw one Radjah Shelduck doing likewise.
Lesser Whistling-Ducks have brown convex eyes.
Radjah Shelducks have a round of white around the brown iris. The white area seems flat. That makes the eyes look like a button.
Both types have eyelids that shut upwards.