ClipArt ETC
"A name often given to various species of Heron, particularly those which, at least during the breeding season, have the feathers on the lower part of the back lengthened and their barbs loose, so that this part of the plumage is very soft and flowing." — Chambers' Encyclopedia, 1875

Egret

"A name often given to various species of Heron, particularly those which, at least during the breeding…