Just another idea (has worked, here, for some years, now. We've only "hung" the "saucers" on lines - but I see no reason that they couldn't be mounted (with small springs, etc.) to the tops of poles/branches/etc.
Turkey hens are the best warning system, however (will "stalk" hawks - brief video shows mottled hen walking right past the Red Shouldered Hawk on the stump - last few seconds hawk takes off in disgust, pooping from displeasure?)
(just another "deterrent" to consider
see you in the turkey forum).