Gourds can make inexpensive, fun bird house projects. If there are gourds being harvested around your neighborhood, be sure to grab one or two!
First, it's important to have a proper, healthy base to work with. Remember, this will be the home for baby birds! Be sure to look for gourds with solid stems, because this will be the roof of your birdhouse. Try to find a gourd with a diameter of 6" or more, to give the birds enough room to fit inside and raise their young.
Next, it's time to prepare your gourd for home construction. Wash your gourd thoroughly with eco-friendly materials. You don't want to put nasty chemicals on the home of baby birds! Plain water should do fine, or if you must, find a baby-safe, very gentle detergent.
Hang the gourd somewhere dry for about a month, so the gourd dries out thoroughly. When the gourd is thoroughly dry, you should be able to hear the seeds inside when you shake the gourd.
Now for the actual birdhouse construction. You want to put a 2" hole in one side of the gourd with a drill, to provide the main entrance for your birds. For drainage, put a pair of 1/4" holes about 1" up from the bottom of the gourd. This helps to make sure, if water gets into the gourd, that it can easily get back out again.
As far as placement, if the entry hole is the "nose" of your gourd, the holes should be on the sides, where the "ears" would be.
Your gourd is pretty much complete now, from a functional point of view! Now it's time to snaz it up a bit, if you wish.
You can paint your gourd if you want, using a lead-free paint of course. Whether you decorate it or not, be sure to use a coat of non-toxic shellac will help your gourd weather the elements.
When you're ready, run a thin wire through the top of the gourd to hang it by, or make a small hole in the back to put on a tree. Hang it in a high tree, somewhere that cats and other animals can't easily get to it. You want this to be a place that birds will enjoy.
Now sit back and watch for new inhabitants!