PHOTOS BY MARK MACEMON ILLUSTRATIONS BY TECH ART & DESIGN
Attracting birds to your backyard rewards you with splashes of color and delightful songs and can even help eliminate bugs.
Establishing a purple martin colony is perhaps the pinnacle of this endeavor, and the only way to do that is to build the birds a residence.
This design is based on a 100-year-old martin house I rescued from an abandoned farmstead. Though the house had never failed to entice these endearing birds, it had flaws. The entrance holes were too big, the porches too narrow and the house itself too hard to clean. (It was nailed to the top of a 20-ft. pole.) But by incorporating a few design changes inspired by modern ornithological research and adding an effective mounting system, I was able to bring this timeless design into the 21st century.
When building a martin house — or any birdhouse — choose wood that’s both rot-resistant and insulating, such as Western red cedar. (Cypress would be another good choice.) Don’t use pressure-treated lumber; you don’t want to expose the eggs or nestlings to the chemicals involved in the treating process. Because the structure will be exposed to the elements year-round, use an exterior-rated adhesive and only stainless steel fasteners.
To start construction, cut the fronts, backs and sides of the nesting levels to size, and bore the 2-in. entrance holes. Then assemble the two nesting levels — I used polyurethane glue and stainless steel wood screws.
Cut the slots for the lap joints in the nesting dividers with a jigsaw, slip the divider walls together and insert the assemblies into the nesting levels, attaching them to the perimeter walls. Then cut and attach the floor panels.
To make the mounting supports, start with two 32-in. lengths of cedar 2x6s. Form a saddle joint by first making successive cuts with a circular saw (with the blade set to a depth of 3/4 in.) and then removing the waste with a sharp chisel. Glue the two lengths together. After the glue cures, bore a 2-1/2-in. hole through the center and two 1/2-in. holes as indicated in the drawing (p. 48). One of these 1/2-in. holes will serve as a guide for the lifting cable, and you’ll attach a 1/2 x 3-in. stainless steel eye bolt that holds the lifting cable through the other for mounting the house. Secure the completed mounting support to the bottom of the first level. Construct the roof assembly by first cutting its floor, roof panels and walls to size. Bore a 2-in. hole in each of the walls, and cover the holes from the inside with fine-mesh screen. Then attach the walls to the floor and the roof panels to the walls.
Cladding the roof
To create the copper roof cladding, first construct a simple sheet-metal break from a length of lumber that has been cut to produce a sharp edge. (You can use anything with a sharp, defined edge as a break, as long as it provides a continuous bending surface.) And though there are a variety of suppliers, we found our copper at Meisel Hardware Specialties (see SOURCES and Shopping List). Cut the copper to size with sheetmetal snips, lay the sheet on the break (allowing a 9/16-in. overhang) and clamp on a second length of wood to secure the copper sheet. Then use a mallet to tap down the overhang. Attach the two main copper roof sheets to the plywood with outdoor-rated construction adhesive, and then glue down the copper ridges. Once the adhesive has set, paint the house white and attach four sets of positive-locking hooks and eyes (two sets per floor), with the eyes screwed into the floors of the second level and the roof assembly, and the hooks screwed into the walls of the first and second levels. These fasteners help to secure the levels to each other once the house is lifted into the air.
Mounting the house
You might be surprised by the weight of a completed martin house — it’s too heavy to haul up and down a ladder. For safety (and because of the need for constant nest maintenance), I use a winch system (see drawing) to raise and lower my martin house. A boat trailer winch from a marine supply store, a pulley and safety strap, a length of steel cable rated for overhead lifting (never use rope) and a long steel pole are all you’ll need to create a safe lifting system. For the mounting pole, use 1-1/2-in. schedule-40 welded steel pipe (1.900-in. o.d., 1.610-in. i.d.). Don’t mount the pole itself in concrete; rather, install a ground socket, which is nothing more than a 30-in.-long section of 2-in. schedule-40 welded steel pipe (2.375-in. o.d., 2.067-in. i.d.). The mounting pole slips easily into the ground socket and makes any pole-repair tasks simpler. To keep the mounting pole from spinning in the ground socket, drill a 7/16-in.-dia. hole 3 in. from the bottom of the ground socket. Insert a 3/8-in. x 2-1/2-in. bolt through the hole and attach a nut. Then cut a corresponding V-notch in the base of the mounting pole. (The notch will sit astride the bolt and prevent spinning.) To mount the pulley, use a hacksaw to cut a slot in the top of the mounting pole as shown in the illustration and drill a hole for the pulley’s bolt. Make a safety strap from flat stock, and attach both the safety strap and the pulley with a 5/16-in. x 2-1/2-in. stainless steel bolt. Drill holes through the base of the mounting pole to suit the needs of the boat trailer winch, but do not install the winch yet. Set the house over the ground socket, feed about 40 ft. of steel cable through the top pulley of the mounting pole (so that the cable is evenly distributed) and insert the mounting pole into the ground socket. Have a helper lift the martin house above the mounting point for the winch; then bolt the winch to the pole. (You can then temporarily rest the martin house on the winch.)
Feed one end of the steel cable down through the house and out the bottom guide hole and attach it to the winch. Pass the other end of the cable down through the house and attach it with a cable fastener (again, rated for overhead lifting) to the eye bolt that’s secured to the mounting support. Latch all of the eye hooks; then slowly turn the winch until you’ve raised the martin house to the appropriate height.
American Birding Association
(719) 578-9703, www.americanbirding.org
Cornell Lab of Ornithology
Meisel Hardware Specialties (copper)
National Audubon Society
(212) 979-3000, www.audubon.org
Purple Martin Conservation Association
(814) 734-4420, www.purplemartin.org
The Purple Martin Forum
The Purple Martin Society, NA
(630) 850-8529, www.purplemartins.com