$1 bird house craft

I've been trying to keep the girls busy this summer and since it's been so stinkin' hot I've needed to come up with indoor activities. I took Maddie to the fabric store with me and she found a clearance bin with little wooden bird houses for $1. She really, really wanted to get one so I caved in.....it was $1 after all. This was a really fun and super easy craft for the girls. They spent a good hour painting their bird houses which is a great amount of time for little ones to sit still and concentrate. I've noticed that the more we paint the better they get at not getting paint all over the table and all over themselves. Charlotte still enjoys coloring on herself with marker, but I can't tell you the last time I got a picture of her with paint all on her face. Progress! They were both super excited for the paint to dry so they could hang their bird houses up, but as of right now they are sitting on our fireplace mantle......I don't want them to get ruined putting them outside in the weather. Anyone have any weather proofing ideas??