Predators aren't going to perform a physical on each potential prey item to ensure they are only killing a weak or old target, they are just going to chase down and kill the first thing they see, sick, healthy, young, or old. That's why they call them opportunistic predators, they kill whatever they have the opportunity to. Habitat loss is a large factor for the upland gamebirds population decline, but it is compounded by predation which suppresses the birds even more. One more predator though that needs some major population control that's doing a great deal of damage is the feral house cat. They are bird killing machines and are pretty bad around here. Dirty cats...