I was out in the yard and just happened to see a bird fly in a vent on the side of my house. It has a cover on it, but the little bastard must be opening it with it's beak. I have been hearing some noises coming from the bathroom that is downstairs, kinda under where this vent is located. I just thought the pipes were making some funny noises, cause it sounds like the noises are coming from inside the toilet. I'm a relatively new homeowner, and I have no idea what this vent is for or where it goes. I know that it's not the dryer vent, because it's on the bottom. I can replace the cover so that it cant get in, but I don't want to trap it in there, that could make my house smell. Here are some pics of said vent, any idea where this could lead, and what I could do to remedy this situation?