In any flock of chickens, there is a pecking order, ALPHA on the top, Omega on the bottom, and everyone in between. Basic flock psychology, is the flock is only as strong as the weakest member. We see this initially with baby chicks, if there is a weak chick, the rest of the flock will eliminate it from the gene pool. “Vote her off the island”, so to speak.
They may do this as adults as well, there may be a bird that they sense needs to be eliminated from the gene pool. This may be a healthy, egg producing hen. One of the ways they do this is to not allow the hen in question to drink. In hot weather they expire pretty quickly. I get phone calls from customers every summer, after the birds were posted, in most cases they died of dehydration. Adding a few extra water stations can easily prevent this, by allowing more options for birds to drink from. This simple step can be the key to keeping the entire flock healthy.