Black-crowned Night Heron
(Nycticorax nycticorax)
The Black-crowned Night Heron has a stocky body, with a comparatively short neck and legs. It has an average length of 20 inches and a wingspan of approximately 44 inches.
The adult has distinctive coloring, with black cap, upper back and scapulars; gray wings, rump and tail; and white to pale gray underparts. The bill is stout and black, and the eyes are red. For most of the year, the legs of the adult are yellow-green.
The eyes of the juvenile black-crowned night heron are yellowish or amber and the dull gray legs lack the colorful pigmentation of those of the adult. The juvenile has a brown head, neck, chest and belly streaked with buff and white. The wings and back are darker brown, though the tips of the feathers have large white spots. The young do not acquire full adult plumage until the third year.
Black-crowned Night Herons are presumed to be monogamous. Pair formations are signaled by males becoming aggressive and performing “Snap Displays”, in which they walk around in a crouched position, head lowered, snapping their mandibles together or grasping a twig. The “Snap Display” is followed by the “Advertisement Display” to attract females. In this display a male stretches his neck out and bobs his head, and when his head is level with his feet, he gives a snap-hiss vocalization. Twig-shaking and preening may occur between songs. Females that come near the displaying male are rejected at first, but eventually a female is allowed to enter his territory. At the time of pair formation, the legs of both sexes turn pink. Copulation usually takes place on or near the nest, and begins the first or second day after the pair is formed.
There is one brood per season. Black-crowned Night Herons nest colonially, and often there can be more than a dozen nests in one tree. The nest is built near the trunk of a tree or in the fork of branches, either in the open or deep in foliage. The male initiates nest building by beginning to build a new nest or refurbishing an old one. The nest is usually a platform lined with roots and grass. During and after pair formation, the male collects sticks and presents them to the female, who works them into the nest. The male's twig ceremony gradually changes to nest building.
Night
Herons are sluggish hunters, standing quietly for long periods of time waiting
for a frog or fish to pass by. They also plunder the nests of other Herons and
make regular nighttime visits to colonies of Terns or