They are the white cattle egrets. They follow my cows around picking up insects as the cows graze but spend the majority of their time roosting on the brush piles in my pond. The main reason that I have been concerned is their sheer numbers. I must have hundreds of them. They are not large birds but if they had a desire to eat fathead minnows I could possibly have a problem. The water in my pond is probably four feet from being full and so any structure that I put in the pond has made good roosting for the birds. I have also noticed that they spend time near my feeder on my dock pooping everywhere. I hope they aren't eating the pellet feeding fish.