If the bald eagles are circling high, they are riding the thermal currents and not necessarily hunting. They might be overseeing their territory, or simply flying for the joy of soaring.
They are capable of taking poultry, and they can handle something as large as a Canada goose. But they prefer to take game off of water or out of the air. They fish and eat carrion. They don't appear to like taking live game off of hard ground. I suspect it is because the take-off is more difficult with those large wings if they are standing where they can't make a down stroke. They can do it, just would rather do something else in a situation where a hard landing and a fast take-off might be needed.
I have multiple bald eagles every day over my property and they have never shown any interest in my birds. Mostly, they are soaring; occasionally, one will fly right across the top of my pens. They apparently have plenty to eat so aren't going after difficult game. If they ever do take an interest in my birds, the birds will be kept under cover during the day. My birds are already under cover at night because I have a Great Horned Owl living on my property.
If you are worried about the eagle, keep the birds under cover for awhile. The eagle can't kill them if he can't reach them.
