Mid-Century Modern Birdhouse by Chris Gardner on Curbly.com
A birdhouse can be as simple or as detailed as you like-from a basic box shape built with butt-joints and a 45-degree roof to one modeled after architecture you love, a miniature version of your current home, or one that reflects your “dream” home (that's mine, pictured above). Honestly the birds don't care what it looks like, they just want a safe home.
The basic DIY birdhouse
Whatever style you decide for your birdhouse, be sure it's made from materials that can stand up to the weather. Cedar or redwood is affordable, comes in 1” x 8' sizes at any home center, and will last for years outdoors. Exterior-grade plywood (which uses a phenolic resin glue to hold the layers together) is also a good option, but don't use treated lumber, as the chemicals can be harmful to the birds. Materials should be at least 3/4' thick to insulate the nest during colder months.
If you're just getting started, a basic cedar 1' x 8' is the way to go: they can cut it for you at the lumber counter, and you can make three or four from a single 8' length. There's also a benefit to using lumber with one rough side as it will actually help young birds leave the next by giving them something to grab onto. And guess what! There's no need to add a little perch to a birdhouse. While useful on a bird feeder, birds don't need them on a house, and they could assist predators getting inside.
To put things together, 6D galvanized nails will work, but I prefer using screws and pilot holes, as the weather will cause the wood to warp and twist and could eventually pull the nails out. Also, be sure that any glue you use is rated for outdoor use.
To finish, use a light stain or sealant and let the wood grain show through. If you prefer painting, be sure to opt for an exterior grade paint in an earth tone color like green or brown; it will help the birdhouse blend with the surroundings and make the birds feel it's a safe place to nest.
Some additional tips for making a “better” birdhouse:
• All birdhouses need to have one wall or the roof detachable so that you can clean out old nests for new families. A bird will likely not use the same spot for nesting twice, and a new bird will not move into a house that hasn't been cleaned.
• Birdhouses can be built with the species in mind. A bird needs to feel safe, and the house and entry should be just big enough. You'll want to size the house and the hole diameter for different species. You can find detailing specific for each bird type at Wild-bird-watching.com.
• Be sure to add a few 1/4' drainage holes in the floor. It will help keep the interior nice and dry.
• Make certain the roof is angled and has ample overhang to keep out any rain.
• Don't rule out an open-front house. Three walls, a floor, and slanted roof are enough for many species who like to hang out on the porch as much as you.
For more on birdhouses, consider:
12 Birdhouses We Love
How To: Make a Birdhouse
10 Feeders for Winter Nourishment