RAH The beak color is only partially diagnostic in that some of the smaller heron/egrets may have dark bills or light bills or a combination of dark and light at different times of their lives. The white morph of the GBH has a yellow bill which is much heavier, thicker, straighter, and appears two toned in good light. Adult GWHs, ie. white phase GBH, in spring have plumes on the back of their heads; the Great Egrets do not. The GWHs also have short plumes on their lower backs, sometimes hard to see, and the egrets have longer plumes there. These plume features are more readily apparent when the birds are on the ground rather than in the air. Two guides I'd recommend are The Sibley Guide to Birds, a National Audubon book, and Complete Birds of North America from National Geographic. Enjoy! This reminds me of our trip down the Rio Lagartos (alligator river), on the northern shore of the Yucatan many years ago. One of our party jokingly would query our panga operator/guide about the flavor of each of the different bird species he was pointing out to us. "!Muy sabroso!" was his reply for every one. When he even answered that way for the roseate spoonbill, a bird that filter feeds in the muck, we KNEW he was full of it!
