The Red-knobbed Coot is much less secretive than most of the rail family, although possibly more shy than Eurasian Coot. It can be seen swimming on open water or walking across waterside grasslands. It is an aggressive species, and strongly territorial during the breeding season.
It is reluctant to fly and when taking off runs across the water surface with much splashing. It does the same, but without actually flying, when travelling a short distance at speed (to escape a rival, for example, or to dispute possession of a choice morsel). As with many rails, its weak flight does not inspire confidence. It bobs its head as it swims, and makes short dives from a little jump.
The Red-knobbed Coot is largely black except for the white facial shield. As a swimming species, it has partial webbing on its long strong toes. The juvenile is paler than the adult, has a whitish breast, and lacks the facial shield; the adult's black plumage develops when about 3-4 months old, but the white shield is only fully developed at about one year old, some time later.
A good view is necessary to separate this species from the Eurasian Coot, with which its range overlaps. There are two tiny red knobs at the top of the facial shield, which are not visible at any great distance and are only present in the breeding season; the black feathering between the shield and the bill is rounded, whereas in Eurasian it comes to a point; and the bill has a bluish grey tinge.
The Red-knobbed Coot is an omnivore, and will take a variety of small live prey including the eggs of other water birds.
This is a noisy bird, but its vocalisations are quite different from the Eurasian Coot. It gives a fast kerrre like the Little Crake, and a harsh ka-haa.