Most raptors will go for easy prey, chicks with a mother are not particularly easy prey as there is a high risk of damage to the raptor should the mother hen make contact (you've seen the damage roosters do to each other - hens are equally well equipped and with chicks often much nastier).
It's a different story when the raptors are feeding young though - then they will take much bigger risks.
We only lose chicks to hawks when they themselves have chicks to feed - the rest of the time they seem happy to eat smaller birds that don't involve screeching mother hens !
As someone has already pointed out, crows and smaller birds can make life intolerable for the raptors by constantly mobbing them and alerting every other bird/squirrel/rat to their presence, so encourage them to your area. You could also try feeding wild birds as far away from your coop as possible, making sure that any self respecting raptor would opt for the smorgasbord rather than ordering 'a la carte'.
In desperation, and it doesn't sound like you are there yet, short of netting over you run you could try a plastic owl on top of your coop, but I don't think most raptors are so stupid not to notice that it never moves. Likewise a plastic snake might deter the less persistent.
Even if you do lose a few chicks, you can be sure the raptors and their relatives are helping keep down the rodents which can only be a good thing.
