The knob-billed duck earns its name from the prominent, bony knob on adult males’ foreheads, especially during the breeding season. This knob, growing up to 5 centimeters, likely aids in mate attraction and dominance displays. Males sport a striking black-and-white plumage: a glossy black head and neck, a white body speckled with black spots, and iridescent green wings. Females, smaller and knobless, share a similar pattern but with muted tones. Reaching up to 76 centimeters in length and 2.5 kilograms in weight, these ducks are larger than most, with a robust build and a heavy, wedge-shaped bill.

Unlike many ducks, knob-billed ducks prefer grazing on land, feeding on grasses, seeds, and aquatic plants. They also perch in trees, using strong claws to grip branches—rare among waterfowl. During breeding, males use their knobs to produce deep, resonating calls, while females nest in tree hollows or dense vegetation. Their bold plumage may warn predators, as their flesh is reportedly unpalatable. Found in freshwater lakes, marshes, and rice paddies, they adapt well but face threats from habitat loss and wetland degradation.

Listed as "Least Concern" by the IUCN, the knob-billed duck remains widespread, though local populations have declined due to wetland drainage and pesticide use. Its unique appearance and behavior make it vital for studying waterfowl evolution, especially sexual dimorphism and non-aquatic adaptations. In some cultures, it symbolizes resilience, while its strange looks have inspired folklore.

As one of the world’s most distinctive ducks, the knob-billed duck showcases nature’s propensity for extraordinary forms. Its bony knob, bold coloration, and quirky habits remind us that even among familiar species, wonders await observation—proof that the natural world is endlessly surprising.