i have millions of crows my neighbors cornfield is right on the otherside of the road i doubt if i would use them to detear hawks though ive heard that they will kill chicks or even small bantys but then my sky has turned completely black on more then 1 ocasion with crows and the noise of there caws and have not lost a free range chicken yet noted i have a 15pund roo but they all run for cover when theres alot of crows