Outside flies are just there. Never have had luck getting rid of them. In the coop we hang vanilla car air fresheners on the first of each month and they work like a charm. You can also sprinkle vanilla extract around ... imitation works just fine. It won't get rid of absolutely all the flies but it will reduce their number considerably. The other thing that helps is using Sweet pdz (horse stall cleaner) on any poopy areas. We spread it over the whole floor of the coop once a week and in the yard in any big poo spots. Works great and is even great for the compost plus the birds can eat it and it adds calcium to their diet. Don't sprinkle it around while the birds are in the coop as they can get sick if they breathe the dust from it while you're spreading it.
