If you wish to attract birds to your yard, placing bird houses targeted to the species you wish to court is a good idea. As the table below indicates, a given species of bird has distinct preferences in terms of size and depth of the box as well as the size of the entrance hole and how far above the floor of the box as well as how high above the ground it is placed.
In general only cavity nesting birds are attracted to boxes. Robins will use a man made ledge, which can be considered a bird house. Birds like Mockingbird, Cardinal, Blue Jay that build woven nests in the canopy will not be attracted to a bird box.
Because of the fastidious nature of city and suburban folks, many of the dead trees that would provide nesting cavities for birds are removed thus, depriving this group of birds a home. By providing man made bird houses you are contributing to the conservation of these species.
Bird House Specifications
*Cover the floor of the box about 2 inches deep in wood chips.
**Fill the box with wood chips. Flickers need to feel that they are excavating a nesting cavity so they need wood chips to remove.
***Back panel is 20" high while front is only 15" high.
#One or more sides of the house are left open so the house is essentially a covered ledge for the bird to build a nest on.
The picture on the right shows a typical house build according to the directions for a Bluebird. The wood used was from an old cedar fence. Cypress wood is the most durable but hard to find. One should not use pressure treated wood intended for decking since the arsenate preservative could be toxic to the chicks. This picture also shows the original 1 1/2 inch hole greatly enlarged by a flicker. This can be prevented by surrounding the entrance hole with a piece of metal flashing.
In constructing your bird house the following points should be considered:
More natural style houses can be constructed from hollow tree limbs as shown in the picture. The hollow tree limb is cut the required height, a proper size hole drilled using a drill bit made for cutting out lock holes in doors. A top and bottom are screwed on and then the house is mounted by attaching a 1x2 to a flattened edge of the house. The whole assembly is then attached to a tree/post via the 1x2.
One can also split a small log then hollow out the two pieces with a chain saw or chisel. Use a metal hinge to join the two hollowed out pieces. Bore an entrance hole and put a roof on and attach the box to a support of choice. Do not hollow out all the way through the log so that you will have a bottom to the cavity.
Gourds are a good substrate for bird houses. First allow the gourd to fully dry out until you can hear the seeds rattle when the gourd is shaken. Drill an entrance hole in the gourd and remove all the seeds and other stringy plant material. Mold can be removed with chlorox/detergent solution with some scrubbing. Rinse well, allow to dry thoroughly and then paint the outside. Drill drainage holes in the bottom and hang at the proper height. The gourd should be prepared several months before its intended use to allow time for thorough drying.