Different hawks migrate, some going pretty long distances. A Google search on migrating hawks might be of interest. Cooper’s Hawks stay in the US over the winter but they can change their patterns during different seasons. There should be a bird watcher’s club around you that could give you information about what the local patterns are. Different hawks have different preferred prey too, but about any that are big enough are a threat to chickens. They will take prey bigger than they are. Cooper’s Hawks are ones that are really dangerous to chickens.
I know you had a bad experience with a hawk, but there are plenty of other predators around. I don’t know how urban or rural you are, I suspect suburban, but any time you let them free range they are at risk. If you chat with your local animal shelter you may be surprised to see what potential predators are common where you are. Dogs are often the biggest risk, not just because they are everywhere but because they kill for fun. They can kill a lot of chickens in a short time. I’ve experienced that. Hopefully you have a good fence around where yours range.
I can’t tell you that they will ever be safe from hawks or anything else when they free range. They won’t. I don’t know how big that risk is for you. Whether or not you are willing to take that risk is your decision. I have seen foxes, coyotes, hawks, eagles, owls, bobcat, raccoons, skunks, possum, and mink here. I let mine free range for three years (locking them up at night) and only lost two, I suspect to a fox. But after two dog attacks from dogs abandoned in the country I put up electric netting to keep ground-based predators away. It worked. In four years I’ve only lost one, to an owl when I was late locking them up one night.
I don’t know what your actual risk is, how precious each chicken is, or how much risk you are willing to take. Many people free range for long periods of time with no problems but the risk is always there. This is not an easy decision.
