Every one of the bird houses that I've built have been made out of scrap wood. I don't follow any particular design, and just expect any bird that wants it can move in and make itself at home!
I've found that each of the birdhouses I've built have been occupied, except for when two bird houses were too close together. I guess the birds have territorial reasons for this. This article describes how I go about building my bird houses and the steps involved.
Select the wood for your bird house
The sources of wood for my birdhouse projects often come from scraps left over from other projects, firewood, and the walls from buildings that I have torn down.
I don't worry about the quality of the wood that I use for the birdhouse. It can even be rough and ugly. My view is the house gets character from the rustic quality of the wood and the birds have yet to complain! In fact, the bird houses with holes and rough spots are actually repaired by the birds!
2: Boards needed for the birdhouse
There are three boards that you'll need to build your birdhouse:
Board #1 will take care of the front, floor, and back of the birdhouse.
Note: It's very important that you select the same thickness of boards for the three parts of the house.
This makes constructing the birdhouse a lot easier. In general, you want to use pretty thin wood. The front of the birdhouse opens up a lot easier if it's thin.
The only drawback to this is the back panel of the bird house is what gets attached to the tree. This board should be thicker to provide more strength, so if you have a board that is the same width, but thicker than the others, use it for the back.
Board #2 is used for the sides of the bird house. This board should be as wide as possible to give the birds more floor space and the house more depth.
Board #3 is used for the roof. The size of this piece doesn't really matter as long as it's big enough to cover the birdhouse when it's done. I've used all kinds of ugly and overly large pieces in the past with good results.
Cut the sides of the birdhouse
Measure an arbitrary distance of x from either side of the board (see the diagram). The value of y should be about 1-2 inches larger than x. This will determine the slope of the birdhouse roof. Use a pencil or a nail to mark the line you need to cut and then cut it.
Cut the wood for the front of the birdhouse
Next, measure the same distance of x as you did for the sides in the previous step. This piece will be used as the front of the bird house (refer to the diagram below). Again, use a nail or pencil to mark the line, and then cut it.
5: Cut the wood for the bird house floor
The floor panel is by far the trickiest measurement in this birdhouse project. The distance of z must be less than the width of the boards used for the sides. This is to make the front and back of the birdhouse flush (see the diagram below).
Mathematically, you should take two times the thickness of the board used for the front and back and subtract that number from the width of the board used for the sides. Be sure to err on the side of z being smaller rather than bigger. The birds will simply fill the floor with nesting materials anyway!
6: Cut the back panel of the bird house
From the original board that you used to cut out the front and floor, cut off another piece of wood longer than side y. This allows for an area to nail the birdhouse onto a tree. I usually make this length 4-5 inches longer than y.
7: Cut out the roof for the bird house
There's not much to say about making the roof. Just ensure that its length and width are big enough to cover the top of the birdhouse. The roof is the last piece to be nailed on, so I don't even think about it until I'm finished with the rest of the birdhouse.
8: Nail the sides of the birdhouse to the back
The order in which you assemble the parts of the birdhouse is important. If they aren't put together in the right order, they won't fit very well.
The first step is to attach each of the sides to the back of the house. Make sure that the roof will still sit flush. Don't worry about any holes, spaces, or gaps. I've discovered that birds like these imperfections and they'll plug anything they don't like with twigs anyway.
Nail the floor to the sides of the birdhouse
The next step is to attach the floor of the house to the sides. Arrange the floor so it meets the back of the bird house. The front end of the floor should be slightly lower than the back end so that any moisture that gets inside can drain away towards the front of the house.
The diagram below shows this in a somewhat exaggerated manner. Also, attach the floor a little higher in the sides so that it's protected from the rain (see the diagram).
10: Nail the front of the bird house to the sides
Of course, any good birdhouse has to have a way to be opened so that you can clean out the previous years nests and drive out any rodents that may have moved in over winter. Therefore, the front of the house also serves as a door.
The front of the bird house is attached by just two nails, which serve as hinges. Notice the red dot on the diagram to see what I mean.
The front of the birdhouse swings open from the bottom. When nailing the front to the sides, be sure to leave a small gap at the top to allow the door to rotate. That way, after the roof is attached, when you open the front the wood doesn't get stuck on the roof.
I can't even count the number of times I've made this simple mistake. See the diagram below for an exaggerated description. It's best to leave as little gap as possible, yet leave room for the top of the door to not get stuck on the roof. The thicker the front panel (the door), the larger this gap has to be. Trial and error will teach you in this regard.
11: Nail the roof to the sides of the bird house
This is a very simple step so long as you can get the roof nailed correctly into the edges of the sides! I usually drill these holes a bit prior to nailing to keep from splitting the sides of the bird house.
The wood that I use for the roof is often oversized firewood which makes nailing pretty difficult! Be sure that you select a roof that is large enough to cover the entire top of the bird house. Both the front and the sides should have a bit of overhang.
12: Drill a hole and insert a nail as a locking pin
As the house is built right now, the front will swing open all by itself. You need to pre-drill a hole and insert a nail that will act as a locking pin to keep the door from opening.
Make sure that you drill the hole larger than the diameter of the nail. Moisture will cause the wood to swell over time which will warp the wood.
If you don't make an oversize hole, you'll probably need a pair of pliers to get the pin out before you can open the door. But you don't want the nail so loose that it falls out by accident. I've actually had this happen on several occasions!
Finally, don't drill the hole deeper than the length of the nail. You'll need a bit of the nail sticking out so that you can grab onto it. You only need to use one nail as the locking pin, and you can place it where you see the green dot in the diagram below.
13: Drill the entrance hole for the bird house
Now you need to drill a hole so that the birds can enter and exit the birdhouse. Depending on the size of the house, I use hole sizes anywhere from 3/4 inch all the way up to 3 inches. I have no idea what species of bird is going to make the house its home, so I just try to build bird houses in a wide range of sizes.
You'll be surprised how often the holes actually become enlarged over the years by birds pecking and chewing at the entrance. When you drill the hole, make sure to stay away from the red hinge nails.
14: Pre-attach the mounting nails
Last but not least, drive in a few nails which you will use to nail the house to a tree or post. I like to put these nails in while I'm building the birdhouse because that makes it easier out in the field to get them attached. I usually use three nails.
Article courtesy of Jason Rickert of Rickert Nature Preserves.
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