Agree with Lisa. I have read about the fishing line solution in several different places. Sounds like a simple, cheap solution to try.
I have 2 resident red tail hawks (which are simply gorgeous). They pretty much spend most their time riding the thermals. Once in a while I get to enjoy their beauty when the spread their wings & sun themselves in a tree out back...very cool
Right now it is the juvenile that is driving me nuts. The silly thing screeches all day to be fed, even tho it is big enough (& does) to feed itself. It has been making some pretty low "fly-bys" in the yard, but, all my birds are 16 weeks, are big enough & seem to know to get under deck (wraps around whole house) / weeping cherry tree.
On that note, there is a fishing line I use (for fishing) that lasts forever and is very strong. I think it's called spider wire or spider line? Has a spider on the box. Way better than regular fishing line so if your gonna do the fishing line thing might try that stuff. A little pricier but I think by like a buck or two. Probably save money in the long run. Ill post a pick later. Going to meijer and they have it.