I have a plastic Eagle Owl on the side of my hut, it has a large stick jammed up his jackson, when there is any wind, the owl moves slightly, not much, but it moves, i also have the radio on in the hut, when the birds are either out or in.
I have never used anything else to keep the b......s away from the hut, they have been spotted going across me but not into the birds when they are out or in the bath.
Am not saying that what i have done is the solution to the problem, but i can tell you its helped me through out the years keeping the birds. :)