It’s a bonanza for bats and spiders.
Are you sure they’re “flies” .. might be fleas.
A guy in Oregon was bitten by a cat who had eaten a rat that was infected with fleas - fleas with Bubonic plague.
Maybe you need to catch a few of these “flies” and have them tested.
Bats are okay outside, at night. Spiders would have to wait until those flies land. Hummingbirds .....