Of the three young cooper's that I have seen, this one seems to be the tallest and slimmest. It is the one that seemed to favour one of its legs, and was often seen perched on one leg with the other leg tucked up heron-like as in the image above.
Reportedly there were four young originally; however, one was reported to have been served up as lunch for the other young prior to us seeing the three remaining young.
A few days ago, we found two of the young, actively chasing Squirrels themselves. The third, again reportedly, was seen being eaten by its siblings a few days ago. I suspect that the young one pictured above is the latest victim of this cannibalistic behaviour.
Many times when one of the young had food, it would repeatedly look up and around as if afraid that lunch might be snatched away by one of its siblings. I've observed the dominant young forcing this one from its meal and then stealing it. There thus doesn't seem to be any love lost between the siblings.