An irregular shaped hole sometimes works as you can see in the photograph. A hole may be cut with an expansion bit or a key hole saw. A few holes drilled in the bottom of the gourd will provide drainage and help keep the gourd dry. Drill a hold through the top and place a thong or wire for hanging. The placement of the hole is very important and one should remember the habits of the birds that you hope to attract.
Most birds like to hop down into the gourd, therefore, place the entrance hole in the upper portion.
This will also keep the babies from falling out should the hole be too low. A perch can be attached just below the hole. A twisted piece of gourd stem or a twig or a cluster of seed pods makes an excellent perch and are in keeping with the natural gourd. After the gourd is cleaned out several coats of varnish or shellac will seal the outer surface. Paint may also be used but avoid the bright colors.