I’m not sure there is a lot you can do. Provide as much cover as possible for the chickens and hope they recognize when the eagles are in the area. I read recently where someone trained a large-breed dog to protect their chickens. Depending on how large an area you have maybe some sort of netting overhead to provide cover is in order?
This does appear to be a big problem, especially with chickens, and one that is very difficult to solve. Bald eagles are bold predators and are not easily discouraged. The problem is you can’t sit and watch for them all day. Perhaps some sort of siren or whistle system can be used, but again, this means someone has to be watching for them. I would provide as much cover as possible and get a large dog to live with the chickens and become their protector.