The other morning I made my first birdhouse and it will work for wrens, I guess. Today I made what will be my tweaked go-to bluebird house.
Some considerations for bluebird houses:
a-The hole needs to be 1.5 for Western Bluebirds & 1 9/16 for Mountain Bluebirds, any bigger and blackbirds will invade.
b-The hole needs to be deep, so if the lumber is 1″ or less, add a section of hardwood with a 1.5″ hole on the facing, this keeps paws from reaching in and beaks from widening the hole- and it stays quieter inside and helps deflect wind.
c-Don’t put a dowel on the front or blackbirds will perch there and trap the bluebird inside to starve them out. Do put a little shallow cut line or two on the facing if the board is smooth, to give the birds a bit of purchase as they enter. On the inside create a ladder of such cuts leading up to and halfway up the hole for the hatchlings to climb.
d-Put a channel cut along the underside of the roof, about 1/4″ back. This line drops any water that may run backward under the roofline.
e-Cut a bevel along the butting edge of the roof, matching the rake of the walls (22%). This ensures a tight fit of the roof to the back wall, as water will otherwise course down the face of the rear riser wall and flood the nest.
f-I used two cheap hinges for the lid, and left a hole open in each hinge to the rear wall. These holes I drilled through, at an angle toward an imaginary post. I will drive the hanging nails through these predrilled and metal faced holes, as I’ve seen many old houses ruined as they split around the hanging nail. There is also a toe of the rear wall under the house with a hole drilled at center for a nail. When hanging the house bring the cordless drill along, and start the holes in the fencepost to keep it from splitting. Barbwire fence posts only, as rail fences allow predators access. Face the house away from prevailing wind/weather, and preferably not facing into cattle, as they may rub it off the post.
g-The roof needs to open for two reasons. One, to clean the nest out in the fall for next season’s hygiene- the birds don’t usually remain paired past a single season, but the female will return to a good nesting site. A light internal sanding is the best cleaning method- don’t use cleaning chemicals ever. Two, so you can check the eggs a few times per week and make sure you haven’t made mistakes in design or placement that need to be addressed. Once the chicks have hatched, keep checking in, but don’t lift the lid after a week or so, or they may become curious and fledge early and die outside the nest box. Bluebirds are very tolerant of people, and allow quiet and calm humans to help them maintain their homes. I have triaged old county birdhouses with nests in them, and the birds are happier with the improvements.
h-The side panels overlap the floor by 1/4″, and float 1/16″ above the floor. This allows water/waste to fall out, and air to flow up. This is my invention, but for thinner boards just sand the four corners of the floor back about 1/8″ or till there are visible gaps.
i-There are pairs of air holes drilled on each side and on the back, plus the front panel is cut at a steeper rake than the sides, and dropped just a hair- allowing more air.
j-Connect the boards by glue, clamp tightly, then create seated tap holes and screw together with deck screws.
k-Create a latch to hold the roof closed. I use a screw on the underside of the roof eve, and two screws in the R sidewall- screwed most of the way in. Using bailing wire I anchor-wrap the roof screw and pull tight with pliers, then hand-secure the wire to the sidewall screws with an under/over bend. This way the wire doesn’t degrade and snap, and a critter like a raccoon can’t open it.