Need to get rid of FLYS!!! they are constantly on the chickens and ducks food. Any ideas?

[speedchicken]

I am not having trouble with flies inside my coop, but all over my yard now. I have had 3 chickens for two weeks, and at first, they were free ranging around my whole back yard, and flies were attracted to the chicken poop. Now that I have the chickens fenced off in a section of my yard, I still have a ton of flies around my coop and my yard. It is pretty warm here, in Portland Oregon, and the flies seem to only be active when it's hot. I have put one of the smelly traps out that you add water to, and it has captured hundreds of flies, but there are still many hundreds around the yard. It seems that the flies have moved into my yard, as they're not only interested in the chicken poop, they's all over my pine trees, vegetable garden, lawn, etc. I have not yet tried the vanilla scented trees, nor DE, and will be trying those shortly, but I don't know what would cause so many flies to come take over my yard.

Thanks.