Step 1. Buy or build your own birdhouse. Find one with a 1 1/8 inch entrance hole, because that size is pretty standard opening for most songbirds.

Step 4.  Use a Dremel tool to round the corks around the entrance hole. If you don't have a Dremel, a serrated knife will work. 

Step 2. Cut the corks in half lengthwise with a table band saw or a sharp serrated knife, which will give you a nice, flat gluing surface. If you want to skip cutting the corks, you can use whole ones. You'll just need more corks and a little more glue per piece.

Step 5. For the roof, glue the cork halves directly on top. If you're patient enough, use a serrated knife to slice the corks into disks for a pretty shingled effect.