The Black-crowned night heron (Nycticorax nycticorax) is a medium-sized heron found throughout a large part of the world. These birds have a stocky appearance as if hunched over, the head tucked down into the shoulders, and they are usually seen with this posture. They are most active at dusk or at night when their ghostly forms fly from their daytime roosts to the wetlands where they forage.
Adult birds have a black crown and back with the remainder of the body white or grey, red eyes, and short yellow legs. They have pale gray wings and white under parts. Two or three long white plumes, erected in greeting and courtship displays, extend from the back of the head. The sexes are similar in appearance although the males are slightly larger. Black-crowned night herons do not fit the typical body form of the heron family. They are relatively stocky with shorter bills, legs, and necks than their more familiar cousins, the egrets and "day" herons. Their resting posture is normally somewhat hunched but when hunting they extend their necks and look more like other wading birds. Immature birds have dull grey-brown plumage on their heads, wings, and backs, with numerous pale spots. Their underparts are paler and streaked with brown. The young birds have orange eyes and duller yellowish-green legs.
Black-crowned night herons are social throughout the year, often associating with other species. In the winter, they roost together. A migrating species, it will fly at night and rest during the day. Black-crowned night herons feed by standing still at the water's edge and waiting to ambush prey, mainly at night or early morning. They also engage in bait fishing; luring or distracting fish by tossing edible or inedible buoyant objects into water within their striking range - a rare example of tool use among birds. During the day they rest in trees or bushes. Young leave their perches to huddle in the nest when it is cold. Black-crowned night herons are territorial and will defend their feeding and nesting territories. Their normal call sounds like 'qua,' 'quak,' or 'quark.' Such calls are most often made during flight or when perching.
