[2] The black-headed duck is the most basal living member of its subfamily, and it lacks the stiff tail and swollen bill of its relatives.

Adult males have a glossy black head and upper neck and a white chin.

Their upperparts are deep brownish black with cinnamon or pale rufous speckles and vermiculation.

Adult females have a dark brown head and neck and a whitish throat, and are otherwise like the male.

Immature birds are similar to the female but have more rufous upperparts, more yellowish underparts, and a pale eye stripe.

[4] It mostly inhabits freshwater marshes whose dominant plant is the sedge Scirpus californicus, and outside the breeding season may be found in lakes, water-filled ditches, and sometimes flooded fields.

In contrast with brood parasitic passerines, whose young are altricial, black-headed duck ducklings are precocial.

After an incubation of about 25 days, the ducklings are completely independent a few hours after hatching and leave the nest.