Often asked this question, I thought it would be helpful to post the answer again, especially at this time of year when we see numerous numbers foraging in our marshes and along the shore. Both species of birds breed on Cape Ann and the coast of Massachusetts.
The first clue is size. Snowy Egrets are small, about the size of the Mallard Duck. Remember the letter S for small and snowy. Great Egrets are much larger, nearly identical in size to that of the Great Blue Heron.
Great Egret (Ardea alba)
Great Egrets have black feet and yellow bills. Snowy Egrets have reverse coloring, yellow feet and black bills.
Great Egrets stand very still while fishing. Snowy Egrets are wonderfully animated when foraging; they run quickly, walk determinedly, fly, and swish their feet around to stir up fish.