Great Egret and "Great White" Heron larger with thicker, yellow bills. Cattle Egret smaller, with shorter, yellow or orange bill and pale legs. The Reddish Egret can be similar as white morph immatures, but has a much larger bill, blue-gray legs and gray lores. Immature Little Blue Heron has a variably gray- or yellow-based bill with black tip and can be similar to immature Snowies that have pale bases to the bills, but always has gray facial skin, green legs and blue-gray primary tips (best seen in flight from below and not always visible at rest). Little Egret, which occurs only rarely in North America, is very similar but has gray facial skin and two long head plumes in alternate plumage.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.