you must understand zoo's.... most (and I mean Most but not all) zoos have animals that are unable to survive in the wild.. They keep animsl that were injured or rescued from capitivity and are unable to survive if released in to the wild on thier own.. some of these animals cannot hunt, fly or defend themsleves... some cannot be released due to imprinting with humans.. if they are comfortable with people they will most likely be killed by them if released.. Some of the birds of prey have , for instance bad eye sight, say from an injury, and cannot hunt for prey and will starve to death if released (like owls). Bad eye sight and poor hunting ability is the number one reason animal end up in zoo's and wild life facilities. But not all the animals you see in the zoos are rehabilitations. It is still controversial..