Crustaceans are the main component of the yellow-crowned night-heron’s diet (2) (3), which includes marsh, mud, swimming, land and beach crabs, as well as crayfish, fish, aquatic invertebrates, mussels and leeches. In drier areas, this species may also take terrestrial arthropods, lizards, small snakes (2), mice, rabbits and young birds (3). Hunting is usually done individually (3), with most activity occurring during the night, or at dusk and dawn (2), especially during the breeding season (4). This species forages by slowly stalking its prey until it is close enough to attack. The individual will lunge towards its prey and capture it within the bill, consequently swallowing it whole, or shaking, crushing or spearing it into smaller pieces (3) (4). The shape and size of the bill varies between each subspecies, and it has been suggested that different populations have evolved their specific characteristics due to the prey availability within their habitat (2).
The courting routine of the male yellow-crowned night-heron involves display flights and neck stretching, which a receptive female may copy (3). Once the pair bond is formed it is thought to last for one breeding season (4).
In the northern parts of its range, the female yellow-crowned night-heron lays eggs between March and June, while eggs are laid later in the year in the south, usually between August and October. Small colonies of nesting birds are common, although this species may also nest alone. The nest is usually built in a bush or tree. The outer layer of the nest is made of sticks, and lined inside with thin twigs, roots, grass or leaves (2). Both sexes contribute to the construction of the nest, with the female staying on the nest site while the male collects sticks (3) (4). As the nest is nearing completion, the female also gathers sticks (4), which are usually taken directly from trees, rather than from the ground (3) (4). The nest is generally complete after around 11 days, and between 2 and 8 eggs are laid by the female shortly afterwards. Females from northern populations generally have a larger clutch than those in the south (3). Both sexes incubate the eggs (3), which hatch after 21 to 25 days (2). Once the eggs have hatched, the male and female share brooding responsibilities (4). The young fledge the nest around 25 days after hatching (2).
All subspecies of the yellow-crowned night-heron are sedentary, except for the nominate subspecies. Nyctanassa violacea violacea migrates from its northern breeding grounds in September to overwinter in Central America and the Caribbean, returning to the north to breed in March (2).