Take care if you have chicks, but they leave adult size chickens alone. In the last week I've seen my neighborhood flock (or would it be 'murder') of crows chase a hawk and a bald eagle off of my block. They're good to have around! I'm a lot more worried about large birds of prey then I am about crows.
(A bald eagle, for goodness sakes!)
(A bald eagle, for goodness sakes!)
