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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 HeronNycticorax nycticorax
A California Department of Fish and Game "Special Animal"
Life HistoryThis 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 ConclusionsThe 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.