I have a small flock of Silkies and ducks, and I just discovered that they have lice. (At least, I think it's lice. They are little yellow bugs.) They had these last fall and I sprayed them with lice killer, gave them bathes, and sprayed down the whole coop. Now they are back! How do you suggest I get rid of them. What brand of lice killer do you recommend? What are they getting this from? Could it be from the mice? Or possibly crows? How do I get rid of the mice in the coop without hurting the chickens or my barn cat? Thanks!