Monday, February 22, 2016

Building a Bird Nesting Box

Yesterday afternoon I built a nesting box for small cavity-dwelling birds.  Over the past decade I have probably built several dozen of these boxes.  They have been placed in school habitats, given away, and donated as silent auction items.  I placed several on trees at our previous home and have one up on a tree near our back door.  These boxes have been used by Eastern Bluebirds, Tree Swallows, Black-capped Chickadees, House Wrens, White-breasted Nuthatches, and unfortunately by House Sparrows.

I like this design because it is relatively easy to built.  It is constructed from a single 6 ft. piece of 1x6 rough-sawn cedar.  I can cut all of the required pieces from this one board and have a couple pieces left over.

Building one of these boxes requires very little in the way of tools.  I use a compound miter saw to cut the wood, but it can easily be done with a hand saw.  The other required tools and supplies are a tape measure or ruler, a hammer, nails ( I use 6D and 4D sinkers), a #3 Phillips screwdriver, one #10 brass wood screw, and a drill with a 1 1/2 inch spade bit.  I also use wood glue or construction adhesive to help attach the boards and a pair of bar clamps to hold things together during assembly.  The glue and clamps are not required, but do make things easier.

The first step is to cut all of the piece to length.  This nesting box requires one 14 inch piece (back), four 9 inch pieces (sides, front, and top), one 3 3/4 inch piece (bottom).

All of the pieces for one nest box can be cut from one 1 x 6 x 6 ft piece of cedar - one 4 x 2 3/4 piece (predator guard),      one 3 3/4 inch piece (bottom), four 9 inch pieces (sides, front, and top) and one 14 inch piece (back).

You will also want to make a predator guard so it is harder for animals to reach or claw their way inside.  The predator guard may vary in size.  A 6 foot board is rarely exactly six feet long.  After cutting the above pieces you should have a remaining piece of lumber that is about 18 inches long. From the leftover piece of lumber, measure and cut a 14 inch piece (this can be used as the back for another box).  The small piece this is leftover can be sawn in half to create two predator guards.  Each will be approximately 4 inches by 2 3/4 inches.

The "leftovers" (one 14 inch board and a 4 inch x 2 3/4 inch piece) are the start to another box

There is one other step before assembly.  I use the compound miter saw, set at 45 degrees, to cut 1/2 inch off each corner of the bottom piece.  This allows for drainage if water gets into the box.

The next step is assembly.  First place the back piece flat on your work surface with the rough side facing up - all rough-sawn surfaces should be on the inside of the box to give the nestlings something to grab onto when they finally leave the box.  On the back arrange the two sides and the bottom.  The bottom should be glued to one of the sides - the other side needs to be able to open.  I place the bottom about 1/2 inch up from the bottom edge of the sides.  Between the top end of the sides I insert a 3 1/2 inch piece of 2x4 lumber (this is used only as a brace to clamp the sides and is later removed) and add clamps to hold the sides and bottom together.  Then add a bead of glue on the front edge of the bottom piece and to the front of the non-opening side.

Clamp the two side, bottom and a removable block together.  Add glue to the front edges of the bottom and one side piece.

Next place the front on the box.  It should be flush with the bottom piece and extend about 1/2 inch beyond the top edge of the sides.  Now it is time to start nailing the box together.  I use 6D nails for assembly.  I pre-drill all nail holes (with a 5/64 inch bit) to prevent the wood from splitting.  This step should require about seven nails.  Two nails will be needed to attach the bottom to the front.  About four are required to attach the front to the one (glued) side.  The final nail will be used on the to attach the other side about 1 inch below the top edge of the front - this side will be used as a door and the nail acts as a hinge or pivot point.

Set the front into place.  Pre-drill nail holes to connect the front to the glued side and bottom pieces and attach with 6D nails.

Do not remove the clamps yet.

The front is now attached to the bottom and both sides.  The block of 2x4 lumber will be removed later - it just acts as a brace for clamping the pieces together.

The next step is to attach the back to the sides and bottom.  First flip the box over onto its front.  Add a bead of glue to the back edge of the bottom piece and to the back of the previously glued and nailed side.

A bead of glue on the bottom and one side (the previously glued/nailed one) will help secure them to the back of the box.

Then place the back into position and secure with nails to the bottom and glued side piece.  Remember to drill pilot holes for the nails to prevent the wood from splitting.  Just as with the front this will require about six nails

The back set in place and ready to attach with nails.

Drill pilot holes before driving nails.  This prevents splitting.

Attach the back to the other side with a single nail.  Then remove the clamps and the bracing block of 2x4 lumber.  You should be able to swing open the one side - the two nails that connect it to the front and back act as pivots.  Close it back up before the next step.

Only two nails hold one side in place and allow it to open like a door.

Now place the box upright on its bottom.  (The back should hang over the edge of your work surface.)  A bead of glue will be added to the top of the front and along the back edge of the top piece.

Glue the top edge of the front and one end of the top before setting into place.

The top can then be set into place.  I use a couple of shims to keep the top a consistent space above the side pieces to provide ventilation.  This is why the front sits higher than the sides. The top can then be attached to the front with nails (pre-drill the holes first).

Shims can be used to ensure proper ventilation space between the top and sides.  Nail the top to the front piece.

The flip the box onto its front - use a small piece of 2x4 and the predator guard to level the box.  The attach the back to the top with four nails.

Flip the box onto its front and level with scrap lumber before nailing the back to thee top.

There is only one piece left to attach.  Flip the box back onto its back and put a bead of glue around the predator guards.  This should then be placed on the front of the box, centered from side to side and flush with the top.

A bead of glue will help secure the predator guard.

The predator guard should be centered on the front and flush with the top of the box.

Use four 4D nails to attach the predator guard to the front - one at each corner.  Do not use 6D nails as they may penetrate through the front and into the box.

A 6D nail and a smaller 4D nail.  The 4D is used to secure the predator guard.

The predator guard glued and nailed into place.

Only two steps remain in the assembly process.  First is drilling the entrance hole through the predator guard and front piece.  This can be done with a manual bit and brace, but is much easier with a power drill.  A 1 1/2 inch spade bit makes an appropriate hole for Eastern Bluebirds and many other species.  I recommend either placing the box on the floor and bracing it with your feet or clamping it to your work surface before drilling

Either clamp the box down or place on the floor and brace with your feet before drilling.

A 1 1/2 inch spade bit is used to make the correct size entrance hole for bluebirds.

The entrance hole is drilled completely through the predator guard and front.

Only one step remains.  A latch must be placed on the door to keep it from being opened accidentally or by predators.  I use a single #10 brass wood screw placed near the bottom of the door as a latch.  A pilot hole should be drilled first and then the screw should be driven in by hand with a screwdriver.

Finally a wood screw is attached to securely close the door of the box.

The nice thing about this basic plan is that it can be scaled up or down for other cavity dwelling species.  In the past week I have also built a box out of 1x10 lumber for Eastern Screech Owls - this box can also be used by American Kestrels and Wood Ducks.  I have also built a large box out of 1x12 lumber for Barred Owls.

From left:  nest boxes for Eastern Bluebird, Screech Owl, and Barred Owl.

Now that you have seen how easy it is to build one of these boxes, I hope you are inspired to build a few of your own for the birds in your neighborhood.

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