Please help, need advice! Bad fly problem from out of the blue!

I need some advice!!! How do I keep these flies away! It is a huge problem!

The problem: I had flies in the yard, then all of a sudden, as if a million fly eggs hatched I have so many flies you can hear them from 5 feet away, when you walk through them they hit you.

The situation: the flies are only in the chicken coop. I free range my chickens so they poop everywhere, meaning that, there is not a huge amount of chicken poop in the coop, more than around the yard, yet not enough to be causing this problem. I have two horses as well, yet there are no piles of poop around the yard because the chickens scratch them down. The flies only gather in the coop and hover in circles all day and disappear at night. There are so many flies it is scary! It was never like this before! I did just increase my count of chickens by 20, but I do not think this is the cause. I keep hanging fly catcher bags around the barn and chicken coop—they are overflowing full and there are still so many flies.

What I think happened: I just built a wood hutch with chicken wire sides and a wooden bottom to keep my baby birds in in the chicken coop. I put a screen sheet over the wooden bottom and dirt over the screen. I did this so that I could pull out the screen and dump the dirt/poop then hose it down/sweep it off before I put it back into the hutch (so for easy cleaning). I think the flies flew into the hutch and crawled under the screen and laid their eggs between the wood and the screen. When I went to clean out the hutch for the first time there were thousands of larvae surviving off the baby chicken poop. I dumped the larvae near my adult birds and they quickly ate up the larvae. Thinking this was over with, the next day there were hundreds of flies in this area and the numbers have only increased since with the population now living in the coop.
Why this is a problem: I am hesitant to redo the hanging fly traps because I do not want another reason for flies to come to this area. Also I am now hesitant to throw fruit and veggie scraps into this area because this is now mass fly food.

Possible solution: I wanted to start growing black soldier flies soon to keep the flies down and then this happened! So if I start growing the flies now (which requires me to keep mass amounts of old food scraps in the back yard to start the population) I feel like I will only be supporting this immense population of flies. A lot of my friends purchase fly predators but this is so expensive!

Briana Stiehl : Without any description of the type of fly infestation you are having, Here is what I Think just happened!

Your flies are all last years flies, they have wintered over within the walls of your out buildings because those were the ones that they could get into!

This is a type of fly that winters over, wakes up as things warm up, and mate, This is an alternative strategy that guarantees That the flies eggs will
not be hatched until conditions are right for them.

Tens of thousands hibernate but only thousands wake up in the spring, usually over a period of a few weeks, you had something change in your
physical layout, (torn down any buildings or cut down a hedgerow?) Or you just got an exceptionally warm clear day when Your local climate should
have been still cool and cloudy !

The old time farmers had an expression for this - Climate is what you expect ! weather is what You GET !

If I am right this will all self correct in a day or two Hope this helps , For the Crafts ! Big AL

Thank you so much Allen this all makes sense. We have been doing a lot of yard work (pulling down trees/shrubs, etc). It has been very hectic and a lot has been changing in the yard in a short amount of time. I looked online after you messaged and I am pretty sure they are bottle flies once reading the online description, which means they do transmit diseases so I hope they leave soon!

Briana Stiehl wrote:
A lot of my friends purchase fly predators but this is so expensive!

Toads. Go down to the nearest pond or creek and scoop up some tadpoles. Bring them back and raise them in some water on your place (a birdbath sunk into the ground, a whiskey barrel, a glazed clay pot, etc). Tadpoles eat algae as they are growing, so you want some nice green water for them. In a few weeks, you will have toads all over the place -- and very few flies.