Yes, the crows did protect your chicks., inadvertently. They are the best babysitters in the world for chasing off hawks. I have an annual nest of ravens (large crows) quite close to my chicken coop for 3 years now that I welcome every spring. Yes, hawks are attracted to your babies and will attack even with you present. A hawk attack can happen very quickly and you may be powerless to intervene in time. Do remember that crows are also predators and will attack and kill young chicks. I have seen the crows and ravens take baby wild turkeys.