Wrens raise two broods each year, and for each brood an apartment is required because wrens do not use the same nest twice. In fact, the second nest is begun before the young birds of the first brood are ready to fly.
If you build one-compartment houses, you must provide two houses for each pair of birds, if you wish to keep them with you during the entire nesting season. Wren houses are often built with several compartments, but not more than one family at a time will take up quarters there because wrens are quarrelsome and do not colonize as martins do. The only advantage of the house with several compartments is that it allows the birds a choice of quarters, and it provides for their two broods.
In the table of dimensions shown in Fig. 668, you will see that the house wren builds its nest usually at a height of between 6 and 10 feet. Bear this in mind when putting up wren houses. Also, place the houses so that the opening faces the East, as that seems to be the preferred exposure.
What size hole should be in a wren birdhouse
Make the opening 7/8 inch in diameter. This is plenty large enough and will keep out the English sparrow.
Such details as these may seem trivial to you, but they are important enough to spell failure for the boy who neglects to consider them.
Wren birdhouse plan No. 1
Wren House No. 1, shown in Fig. 669, is to be suspended from a tree limb. Figure 673 shows a cross-section and Fig. 674 shows dimensions for the parts required. Box boards 1/2 inch thick are good enough working material. Bore the doorway where located in front piece A, and bore a 1/4 inch hole below it for the perch-stick.
The rear wall is of the same size as front A; side B is of the same size, also. Side CD is 1/2 inch shorter than B, because B laps over its edge; it is sawed into three parts, the outer pieces (C) to be nailed in place, the center piece (D) to be slipped between and held at the top by a block (G, Fig. 673), and at the bottom by a button (H) made of a scrap of tin.
Roof board F is the same as for board E (Fig. 674), but is 1/2 inch narrower to allow for the lapping edge of board E. Nail the parts together with i-inch finishing-nails.
Use heavy wire for a hanger, and run it through holes bored through the house ends just below the roof. Make the holes large enough to serve as ventilators.
Wren birdhouse plan No.2
Wren House No. 2 (Fig. 670) is shown in cross-section in Fig. 675, and Fig. 676 shows dimensions for the parts. Bevel the top edge of front piece A, as shown, so the roof will fit it squarely, bore a 7/8-inch doorway in the position indicated, and bore a hole below it for the perch-stick.
Assemble the pieces as shown in Figs. 670 and 675. Hinge back E to the edge of roof board D, to give access for cleaning the house.
It is not necessary to provide a fastener for the hinged back, because when the house is hung upon a tree trunk by passing wires through holes bored through sides B, as indicated in Fig. 675, running these around the tree and fastening them, the back cannot open.
Wren birdhouse plan No. 3
Wren House No. 3 (Fig. 671) is made of a tomato can (A, Fig. 677), a tin funnel 5 1/2 inches in diameter (5), a wooden framework made of three strips (C and D) and two dowel-sticks (E), and a hanger stick and screw-eye (F).
Sticks D provide a means for fastening the funnel roof. Bevel their tops to correspond with the pitch of the funnel, and punch a pair of holes through the funnel, through which to drive screws into the sticks. Bore two 1/4-inch holes through stick C, for perch sticks E. Cut hanger peg F to fit the funnel spout, drive a screw-eye into its top, and fasten the peg with a brad driven through the spout.