You can check for lice and mites at night time when they are roosting and you have a headlamp on. Check around the vent, under the wings, and under the neck feathers. Any little critter will quickly run away so keep your eyes peeled.
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Sometimes poop does get stuck on the feathers. You will need to clean it off with warm soap water/bath. If it is cold outside, you will have to dry her off completely before returning her outside but if it is summer and during the day, she will dry off in the sun.
You will want...