same situation, i get cardinals and other birds in my coop occasionally .. yeah wild birds can introduce lice and disease .. two things, 1) i measure my feed so theres not much left in there and for sure so its cleaned out by evening when birds are most active, that will eliminate most of it .. and 2) its good practice anyway to spray the coop out daily with water, i hose it down good that eliminates most pests believe it or not, but in the warmer months while the chickens are out free roaming about every 2 months or sooner if theres an issue, i get a pump up sprayer and some good pesticide like Bifen and coat the entire coop, corners rafters everything and ground around it, nest boxes to and redo those .. there needs to be time for it to dry before they get back in it .. that works beautiful, controls flies and mosquitos around the coop to ..