A smallish, tawny, bulbous-headed duck that sits low in the water, its tail often flush with the surface, giving it a distinctive appearance. When seen well, the white patch at the base of the bill is diagnostic. The namesake white back is usually visible only in flight. Partially nomadic; small groups are found on pans and pools that have emergent aquatic vegetation, especially waterlilies. Mostly quiet; rarely gives a squeaky-toy-like “swit-swit” whistle.