Snowy Egret

A de­clin­ing species in Florida

RSWLiving - - Contents - BY WIL­LIAM R. C OX Wil­liam R. Cox has been a pro­fes­sional na­ture pho­tog­ra­pher and ecol­o­gist for more than 35 years. Visit him on­line at william­cox­pho­tog­ra­

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. De­clines in snowy egret nest­ing pairs 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 de­cline 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, but-

Many sci­en­tists be­lieve that the mag­ni­tude of Florida’s snowy egret nest­ing de­cline over re­cent decades is the re­sult of ex­ten­sive wet­land de­struc­tion and al­ter­ation.

ton­bush, Brazil­ian pep­per, Aus­tralian pine and pond ap­ple. Nest­ing oc­curs in mul­ti­species 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 needs 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 5- to 7-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 con­di­tions.

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