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Stanislaus River Report
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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
Snowy EgretEgretta thula
California Department of Fish and Game "Special Animal"
Life HistoryThe snowy egret is 24 inches long with a 41 inch wing span (National Geographic 1983). This white marsh bird has a black bill and black legs with yellow feet. During the breeding season the feet become bright orange and plumes develop on the head, neck, and back. In contrast, the great egret is larger with a yellow bill and black feet and the cattle egret is slightly smaller with a yellow bill and completely yellow legs. The cattle egret also develops plumes on the head, neck, and back but they are orange in color.
The snowy egret is widespread in California along shores of coastal estuaries, fresh and saline emergent wetlands, ponds, slow moving rivers, irrigation ditches, and wet fields (Granholm 1988). Snowy egrets feed mostly on aquatic species by walking around to stir up food items. The diet consists mainly of fish, amphibians, snails, and crustaceans but they will also eat lizards, insects, and small rodents when available.
The courtship display involves the male showing off coloration to entice a female. In full display the body is bent forward and downward, the neck is held in a graceful curve, the feathers of the head are raised in a vertical crest, the breast plumes are spread forward and down, the wings are partially open and raised, and the plumes of the back are elevated and spread with their curving tips waving in the air (Bent 1963). Even after the eggs hatch the male will occasionally greet the whole nest in this fashion.
Snowy egrets nest in rookeries built in low growing marsh plants or trees. Nests are constructed from sticks and woody debris, typically about five to ten feet above the ground, but they may be up to 30 feet off the ground (Palmer 1962). Isolated patches of tall willows appear to be the preferred nesting habitat. This bird breeds late March to mid-May in southern and central California (Gill 1977), and late April to late August in northern California (Granholm 1988). A clutch of three to four eggs is laid and incubated for 22 days.
Findings and ConclusionsThe snowy egret is designated a "Special Animal" because it is closely associated with a habitat that is declining in California. At the turn of the century plume hunters had reduced snowy egret populations to small numbers; populations have since regained their normal stature but concern about rookery habitat still exists.
Any project that affects the already inconsistent riparian corridor along the river would have a direct effect on egrets and because rookeries are the main concern with egrets, any project affecting the riparian areas may influence egrets. CDFG biologists did observe snowy egrets and although no rookeries were observed there is a potential for future rookery sites in some of the thicker riparian stands and additional surveys would be required.