Chicks are more vulnerable, not just becuse they are smaller, but more importantly, because they don't know any better. If you free range it helps to keep a "flock" of chickens with the appropriate number of cocks that keep watch. Hatch with broodies and let the brood be part of the flock from...
Hawks start at the head and work down the neck. Mine take a few nibbles from the breast and then they are done. It helps to have flock with a rooster who is a good lookout. If the chickens are free ranged with room to manuever and are hawk wise, the loses should not be toogreat, at least that...