We have Barred Rocks that are 18 weeks old and last week while they were free ranging, a hawk flew over and swooped down at the flock. The rooster sounded the alarm and they headed for cover. The hawk just "buzzed" the chickens not really trying to catch one. The chickens are as big as the hawk and are probably heavier than the hawk. Will this hawk kill my chickens if he gets an opportunity? I always though full grown chickens were safe, but I am fairly new to this.