Another great way to take on the flies in your back yard is to put some kind of flytrap in place. There are all kinds of traps -- some use liquid, some are electrical and others use some kind of food source as a bait. Typically, they all function by luring flies into a confined space and either keeping them there or killing them instantly in some way. Many of them are reusable and most are environmentally friendly.
The University of Arizona's Center for Insect Science Education Outreach even has great tips on how to build your own using a two-liter soda bottle and some raw meat. It's time to take back your house (and your yard) from the flies!