Sorry to hear about your problem with hawks, but you are right it probably is all the fields that attract them. I wish I could give you a solution other than leaving them locked up. We have trees for them to hide under, and that is probably why we don't have the problem with hawks. Fisher...
If you live in Sturbridge MA, I live right next door to you. In the 3 years I have been keeping chickens, I have only had one hawk incident. That happened in the middle of January when I think food was really scarce. I don't know what keeps them away. I let my chickens out every afternoon...