Identifying hawks is REALLY hard. The male and female of the same species are such different sizes (the female is about 50% larger than the male); the plumage differs from juvenile to adult, often from male to female; and worst of all, you generally just get a brown blur out of the corner of your eyes.
But, if you know what hawk is hanging around, you can get an idea of how dangerous it is. Hawks are everywhere whether you see them or not.
You are really lucky if you have crows around. I wish I did. A friend near Seattle feeds her wild crows to encourage them to stay very close to her chickens--she calls them and they come. She feeds them dog food to keep them around. Crows will mob a hawk and drive it out of the area. They will take a chick, but adult chickens should be safe with crows. (Ravens are a different story--they are very large.)
By buzzards, do you mean vultures? (Buzzards are an Old World hawk, not a vulture.) Vultures won't bother your chickens. I'm not sure about the Caracara, which hangs around with vultures, acts like a vulture but isn't one. I think they do take small animals, but don't know if a chicken is too big.
I don't think a Red Shouldered hawk is much of a problem for a large fowl chicken. I think the most common hawk to be a big risk is a Coopers and a Red Tailed. The Coopers is quite bold, too. Coopers and Red Shouldered hawks are about the same size.
