We have 4 chicks from the same hatch that were in our house in a 4 x 5.5 ft area. This Saturday we let them outside in a pen of them same size for the day because it was about 70. While they were outside, we set up their outdoor brooder, which is one of our small sheds. It is 4x8 ft. Today I noticed that one of them has a crusty spot on their back. I've posted this picture a couple other places and have heard every guess from from being mounted to dogpiling to pecking to boredom from too small a space. Any thoughts as to what might be the cause???
