Stanislaus River Basin and Calaveras River Water Use Program
Threatened and Endangered Species Report - March 1995
Bay Delta and Special Water Projects Division, CA Dept of Fish and Game
Black-crowned Night Heron
Nycticorax nycticorax
A California Department of Fish and Game "Special Animal"
Life History
This stocky heron has a short neck, is thick-billed, has short legs, and is usually hunched
and inactive. It measures 23 to 28 inches in length with a wingspan of 44 inches. The adults
have a black back and cap which is contrasted with pale gray or whitish underparts; full adult
plumage is not reached until the third year. The immatures are warm brown in color and are
streaked and spotted with buff and white. When breeding, the birds have two long white head
plumes. The flight of the black-crowned night heron is different from that of other herons and
is more gull-like (Bent 1961). Its flight is strong, direct, and generally swifter than other
herons. The black-crowned night heron is a fairly common yearlong resident of the foothills
and lowlands throughout most of California.
Nesting takes place in thick-foliaged trees, dense fresh or brackish emergent wetlands, or
dense shrubbery or vines near aquatic feeding areas. The nests are built of twigs or various
marsh plants and the clutch size is three or four, occasionally five. The incubation period is
24 to 26 days after which the young are cared for by both adults. The first flight attempts
made by the young take place at six weeks of age but they are not independent for some time
after that.
The black-crowned night heron feeds primarily at night. Foraging is conducted largely
along the margins of lacustrine, riverine, and fresh and saline emergent wetlands. The highly
variable diet consists of fishes, crustaceans, aquatic insects, other vertebrates, amphibians,
reptiles, some small mammals, and rarely a young bird. These birds hunt in shallow water
waiting motionlessly, but just as often they stalk their prey.
Findings and Conclusions
The black-crowned night heron has been designated a "Special Animal" because of its
close association with a habitat that is continuing to decline in California. Additionally, any
human disturbance of nesting colonies results in nest abandonment.
There were no reported observations of black-crowned night herons and no known
black-crowned night heron rookeries occur along the Stanislaus River, however, they could
potential occur. Any project affecting the riparian corridor has the potential for impacting
potential nesting and foraging sites of this species.
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