Flat Dark

I found a screech owl that has these flat dark brown winged parasites on it, what are they?

I’m a licensed wildlife rehabilitator, so I’m allowed to have this bird, so please no rude remarks about keeping it, I’m just not sure what type of bugs these are, Thanks.
I know that they aren’t fleas, or anything of the like, they are about 1/2 an inch in size. Like beetles but not…. wish i had a picture. They move very fast in and out of it’s feathers, just crawling all over.
I found out what they are, they are called flat flies. I wasn’t sure if they were harmful or not, but they aren’t. I consulted with another wildlife rehabber through my network, and she told me what they are. PS My owl will live, but I got him just in the nick of time, those flies are a sign that he was on the ground for a few days. His wing is broken in a bad place and will never heal the right way, so unfortunately he is non-releaseable, but he is going to be my new education animal so he will live out a healthy and safe life with my 3 other screech owls. Thanks for everyone helping.

I forget what they are called but they are parasites and are only on injured or sick birds. Years a go I found a pigeon with them and took it to the vet, they dipped the bird in a bath of some kind and it killed all of those things. The bird did recover.

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