The Carlisle Mosquito Online

Friday, October 1, 2010

 

Great Egret Ardea alba

 

(Photo by Tom Brownrigg)

On August 25, Judy Asarkof of River Road said that she had seen many Great Egrets in the Greenough wetlands near Maple Street. D’Ann and I later counted 19 Great Egrets and several Great Blue Herons, mostly on the west side of Maple Street. We stayed in the car and took photographs so as not to disturb the birds. We had seen Great Egrets previously in Carlisle, the most recently near Maple Street on September 18, 2005. In mid-August of this year, other birders reported seeing Great Egrets at the Carlisle Cranberry Bog.

The Latin genus name Ardea refers to birds in the family Ardeidae, the herons, egrets and bitterns; the species name alba means “white.” The word “egret” is from the Old French aigrette, and referred to a “fowl, like a heron” and is a diminutive of the Old French aigron, which is equivalent to hairon, or “heron.”

Great Egrets usually nest in colonies with other herons and egrets. They build stick nests near the top of a tree or shrub, and sometimes on the ground. They lay from one to six eggs, usually three. In New England, Great Egrets nest as far north as southern Maine, and there are a few large nesting colonies on islands in Massachusetts. According to birder Jim Berry of Ipswich, over 100 pairs of Great Egrets and up to 300 pairs of Snowy Egrets nest on two offshore islands in Essex County. The number of Great Egret nests has increased substantially on one of these islands since 1990, when 25 nests were found.

Great Egrets are “generalists” (not fussy eaters) and will eat fish, crustaceans, and other small vertebrates such as frogs, tadpoles, snakes, small mammals. They also eat aquatic worms, dragonflies, damselflies and aquatic beetles. In Florida, Great Egrets are often seen in suburban habitats searching for anoles (small lizards).

Great Egrets sometimes undergo large migrations known as “postbreeding dispersal” after the breeding season. According to the Cornell Lab of Ornithology, “On the Atlantic Coast, individuals from North Carolina to Florida colonies disperse farther north than birds from more northern colonies (Rhode Island to Virginia), dispersing along the Atlantic Coast commonly as far north as coastal Massachusetts; large numbers appear inland in some years…”

A very large flight (more than1,500 birds) occurred in Massachusetts in 1948; this flight was believed to be a result of a large increase in southern populations following the end of plume hunting.Droughts in southern breeding areas may also trigger migration of birds to northern areas in search of food. Migrating birds often follow coastlines and larger rivers. The Great Egrets seen in Carlisle might have dispersed inland from coastal nesting colonies or from further south.

Before the mid-nineteenth century, the Great Egret was common and widely distributed in the U.S. Later in that century, egrets were killed in large numbers at nesting colonies for plumes used to decorate ladies’ hats. In 1896 Bostonians Harriet Hemenway and Minna Hall founded the Massachusetts Audubon Society in an effort to end the practice of plume hunting. Similar organizations in other states followed, eventually forming the National Audubon Society (a separate organization). Legislation passed in 1910 finally ended most plume hunting, and populations began to recover by 1920.

Great Egret populations appear to be stable, and are probably increasing. Whereas nesting areas are protected, wetland foraging areas are equally important and must be protected.

The writer thanks Jim Berry for information on egret nesting sites in Essex County.

Sources:

Gruson, Edward S., Words for Birds, Quadrangle Books, 1972.

Mccrimmon, Jr., Donald A., John C. Ogden and G. Thomas Bancroft. 2001. Great Egret (Ardea alba), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/570

Veit, Richard R. and Wayne R. Petersen, Birds of Massachusetts, Massachusetts Audubon Society, 1993. ∆


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