I have two silkie hens and I noticed on both that they had small black (some are red) bugs crawling around the vent area. They are kept in a cage with wire and sawdust underneath the wire. They are both in a large cage together. They are let outside for about an hour a day always under my supervision. Their vents also look dirty, they both have droppings caked around the vent area. I don't know what they are or what to do about the bugs. Is there some way I can kill the bugs? And how do I figure out how they got them, they have not been in contact with any birds (except each other). Please help, these are my show birds.