Right now you can see snowy egrets in just about every marsh on the Cape. Often they will be feeding or standing together and may be young egrets from the same nest. They will not stay together forever but seem to benefit from being in the family group for a few more weeks. They will continue to feed almost continually until they are ready to migrate south sometime later this fall.
Snowy's have dark legs and yellow feet. Young ones may have legs that look somewhat greenish or goldish and not as dark as those of adult egrets. They also have a black bill and stand about 2 feet tall. If you are seeing white herons the size of great blue herons they are most likely great egrets but check a good bird book for details since other herons, both immature and mature can be easily confused at this time of year.