Making bird houses is a great activity for the entire family. It provides birds with additional nesting opportunities and gives you unparalleled bird watching opportunities.
There are a tremendous variety of nest boxes designs. They come in all sizes and materials.
But let's think a minute about why we want to build a bird house and what we hope to accomplish.
If the box is too small, the birds will not use it or it may become so crowded as the young grow.
They may not be injured, but a crowded box is hard for the adults to keep clean and it is more difficult for chicks to stay cool. It is possible that young are forced to fledge prematurely.
Some believe that larger boxes help the birds exercise more, so they are more capable of flying when they fledge.
If the box is too large, the birds may not use it because it is too vulnerable to predators or it may attract too much attention or be difficult to support.
Every nest box needs a roof (though many natural cavities are open on top). Our choices are fairly simple. Flat or a sloping; overhang or flush.
It appears that in most cases (there are lots of nest box designs) that 1 inch overlap on the sides and 2 inch overlap in the front is adequate for protecting the occupants from the elements (rain) and increasing the boxes longevity by keeping the box dry.
Another main function of the roof is to provide shade for nest boxes that are exposed to the Sun, especially in warm climates.
So the roof should be sloped to help water runoff (as close to 45 degrees as possible), and it should be overlapped to let water drip away from the box and to provide more shade.
If you plan to place your box in the open (bluebirds for example) in a warm area, you should consider a double roof to keep the box cooler. The two roofs should be spaced to allow air to circulate between them. It has also been suggested that a second side wall be added to also shade the west side of the box.
Front of Nest Box
Most nest box plans have a perpendicular face, but recently, several designs have a sloping front.
What kind of Hole for the Nest Box? Round, Oval or Slot? One hole or
Believe it or not, several bird house designs have more than one hole.
Advantages? Both adults can feed young at the same time - one adult doesn't have to waste energy & time flying around.
A second hole may prevent the strongest chick from dominating access at the entrance hole.
Also, if predators or house sparrows get in the nest, at least the adults have a chance to escape through the second hole.
If ventilation is an issue, the second hole also acts as a big vent. Well, at least I have convinced myself... the next box I build or modify will have two entrance holes.
Disadvantages - May allow easier access by predators and weather (rain).
Some of the research seems to indicate that Bluebirds are attracted to the oval hole (more than the Peterson box shape).
There are conflicting data about the slot hole design and access for house sparrows. Some say the slot entrance discourages house sparrows and others have found that house sparrows readily use them.
If you have trouble with squirrels, then make sure you install a hole guard or restrictor to prevent squirrels from chewing the entrance hole larger. Squirrels will kill and eat nestlings if they get access.
The building materials don't necessarily have to be wood. I guess we could use the recycled plastic material that is being used for decks and fences.
Nest boxes can also be made from PVC pipe or plastic buckets, but those are different plans to be covered later.
If you have access to redwood or cypress or even cedar, that's great. Those types of wood will last a long time, but they can be expensive. Hardwoods will last longer than soft woods, but they can also be expensive.
Treated wood (softwood) will last longer. But is treated wood safe to use for bird houses? The EPA website says treated wood is safe to use in vegetable gardens and on picnic tables, but it is not safe to use on cutting boards, counter tops or bee hives.
CCA treated (Wolmanized). This material was stopped from use in residential construction in 2003, Canada.
I have seen web sites that claim treated wood releases "dangerous fumes" and should not be used when making bird houses. They do not cite the source of this information.
Another website says that only untreated wood should be used in case the birds "gnaw" on the wood. Except for parrots, birds are not generally known for gnawing, but they do peck at the wood (That is how woodpeckers and chickadees excavate their nest cavities).
The Purple Martin Conservation Organization recommends: "Only untreated wood (no pressure-treated wood, no chemically-treated wood, etc.)" when making bird houses.
Since birds are well known to be very sensitive to environmental pollutants (remember the canary in the coal mine?), let's not take any chances. Only use untreated wood.
Nest Boxes can be made from solid wood stock, plywood, bark slabs or solid
Many of the nest boxes I built in the past were made of plywood, because I always had scraps of plywood handy.
Many plans recommend using plywood (exterior grade plywood) and some even preserve the wood with spar varnish.
Nest boxes can also be built by using exterior slabs (slab lumber) that still have the outside tree bark when the tree is sawn up to make lumber.
Solid logs can also be hollowed when making bird houses.
I have done this by first splitting the log, then hollowing out each side, drilling an entrance hole, then joining the two halves back together with wood glue and screws.The log bird house pictured on the right was not split, but hollowed out.
Follow the link below for the complete plans:
Thick or thin wood stock for Nest Box?
When making bird houses, the thickness of the stock determines the thermal insulation of the next box. It can get cold in the Spring and always gets hot in the Summer sun.
A one inch thick box will protect eggs and young from temperature extremes more than a half-inch thick box. This doesn't mean that a half-inch box is useless (I have a half-inch thick blue-bird box that fledges 3 or 4 tree swallows most seasons).
Thicker stock is also heavier and more expensive than thinner stock, but it will also create a sturdier box if constructed properly.
Any stock thickness between one-half in up to one inch should be acceptable for a nest box. If your area is notorious for cold nights in the Spring or if your nest box is to be placed in full sun (with no shade), you may want to go with thicker stock or to provide more shade, use two layers of thin stock with spacers between them for roof and west side.
We all like the feel of a smooth sanded wood, but the truth is, the birds benefit from a rough surface.
A rough surface helps the adults to cling to the side of the box when bringing the nesting material and when feeding the young. It also helps the young scramble out of the box when it is time to go. Rough up or score the wood inside the hole so the chicks can scramble out. Many Wood Duck plans recommend that a "ladder" be made from welded wire or scored into the wood.
If rough wood helps the birds to "hang on", wouldn't it help to add a perch? It probably would... but it also helps cats, raccoons, snakes and other nest predators to hang on to the perch while they fish around inside for something to eat.
We recommend not putting a perch on your bird houses. The birds don't need it and it just makes it easier for predators to get inside the box.
Here is a Bird House Dimensions Chart for 34 species. It is important to design the right type of bird house for different species of birds. It's also important to know the correct hole size so you can discourage species (i.e., house sparrows, starlings, etc.).
We will be expanding our "Making Bird Houses" page as we further our research as well adding pages for specific bird house plans.
Enjoy making your bird house and the birds that make them their home!
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