I tried decoy owls that turn their head and make noises when movement is detected but it took the hawks about a month to figure that out.
My rooster is a tiny silkie who alerts me when he sees hawks, and has successfully beat a fully grown red-tailed hawk on at least one occasion, but 80% of the time if a hawk gets that close, a chicken ends up being the hawk's next meal.
My end solution was to cover my entire freerange area in a 50'x50' poultry net which cost only $30