Snowy Egret: A Declining Species In Florida
Oct 28, 2018 08:20AM
The snowy egret (Egretta thula) is found sporadically throughout the United States. Its summer range extends from southern Montana to northern California, central Tennessee and Kansas, east to the Atlantic coast as far north as Maine. It is found throughout the peninsula of Florida, more commonly along the coast than inland. This heron is rare or absent in the southern Keys.
It winters in North America along the Atlantic coast from Florida to South Carolina, along the northern gulf coast, and from northern California to Arizona. It occurs as far south as central Argentina and southern Chile.
At 24 inches long with a wingspread of 39 inches, the snowy egret is about one-half the size of the great egret. It has all-white plumage, black legs with yellow feet and a black bill with a bright yellow base that extends back to the lores and eyes. The immature snowy has greenish legs that may have a yellow streak on the back. During the breeding season adults have prominent white plumes (aigrettes) on their head, neck and scapulars.
These plumes were once sought-after and led to snowies being hunted almost to extinction during the late 19th and early 20th centuries (1880-1910) in all of North, Central and South America. Prohibition of the plume trade mostly from 1910 to 1913 helped the snowy egret and other species with plumes to recover in most regions.
Snowy egret populations in Florida reached peak numbers during the the post-plume era between the 1930s and early 1950s, but nesting numbers declined at a faster rate than other small herons after 1950. For example, the traditional colonies in the Everglades, numbering 10,000 nesting pairs in the 1930s, declined to 4,500 pairs in the late 1970s and 1,500 pairs in the late 1980s. Snowy egret nesting pair declines were observed throughout Florida during this same era.
The Florida Fish and Wildlife Conservation Commission (FWC) lists the snowy egret as a Species of Special Concern. Many scientists believe that the magnitude of Florida’s snowy egret nesting declines over recent decades is the result of extensive wetland destruction and alteration over large ecological landscapes. These impacts appear to be more severe on foraging habitat than on colony sites, especially in the Everglades basin.
Nesting, which usually begins in March or April and can last through August, has been documented in 43 counties in Florida but is variable in northern counties and the western panhandle.
The snowy egret nests in both inland and coastal wetlands, especially in mangroves and willows, as well as cypress, buttonbush, Brazilian pepper, Australian pine and pond apple. Nesting occurs in multi-species colonies including cattle egrets, great egrets and tricolored herons, most often located on islands in coastal lagoons or shrub-covered wetlands over shallow waters.
Each nest, loosely constructed of sticks, contains two to five light bluish-green eggs. The snowy produces only one brood per year. The male and female share in incubating the eggs for 20 to 24 days. The young leave the nest 20 to 25 days after hatching. Asynchronous hatching often leads to starvation of smaller chicks if food is not available. The snowy egret requires shallow water for foraging throughout the nesting period, thus requiring many nearby wetlands with fluctuating hydroperiods. Therefore, it is critical that a wide variety of wetland types and water depths with abundant prey are available within a five- to seven-mile area of nesting colonies to support nesting success.
In its feeding strategies, the snowy egret displays diverse foraging techniques and active pursuits of prey compared with other herons and egrets. It uses its yellow feet to stir up the bottom sediment to flush its prey. It also follows other wading birds, including glossy ibis, to glean for prey. It feeds on aquatic insects, grasshoppers, prawns, crayfish, worms, shrimp, fish, frogs, snakes and small rodents. Several studies in South Florida found the most important prey to be prawns and many types of small fish 20-40 mm in size, including least killifish, several topminnows, sailfin molly, flagfish and mosquitofish.
Conservation and management practices to protect snowy egrets should include enforcing international, federal, state and local laws and treaties that protect migratory and nongame birds. A wide variety of wetland sites should be available regionally with different water depths and different annual hydroperiods to provide a population of birds with options for foraging and nesting sites during a range of wet and dry rainfall conditions.
William R. Cox has been a professional nature photographer and ecologist for more than 35 years. Visit him online at williamcoxphotography.com