Tree Branch Box Update

Frank Zuern

Since the diagrams for this nest box were published in Sialia 16(l):13-19, the box has been used in many areas and numerous comments have resulted in optional improvements to the original design. The two shown here are a removable predator baffle designed by Svante Humbia and a construction change to allow the box to be opened from the side, rather than from the rear.

Removable Predator Baffle--The predator baffle for the Tree Branch Bluebird Box can be made removable for cleaning or inspecting the contents of the box (Figure 1). Fasten in two wood dowel rods, each one 1/4 inches (0-6 cm) in diameter by 1 1/2 in. (3.8 cm) in length. Glue in place (A). Countersink two holes in the floor to receive the ends of the dowels; allow for clearance. Fasten in place through both sides of the nest box using galvanized nails or screws(B). Use this option with the rear-opening box. Make fasteners (B) removable.

Note: Install the dowel rods 1 in. (2.5cm) into the baffle and let them protrude 1/2 in. (1.3 cm) to fit the holes drilled into the floor. Dimensions of Figure 1 are L-3 3/8 in. (8.6 cm); W-3/4 in. (1.9 cm); H-2 1/2 in. (6.4 cm).

Side-opening Option --The original design has a back door access. That design slows the removal of old nest material. It also limits the opportunity for photography, may impede those who are banding nestlings, and is awkward for people with large hands. The overwhelming advantage of a rear door is that it makes for an efficient House Sparrow trap. Once the sparrow is trapped and the entry plugged, the bird cannot escape when you reach in from the back. Editor's Note: The Technical Advisory Committee warns that monitors may be bitten by a mouse, snake, or other inhabitant because it is difficult to see inside the box from the rear.

To convert this box to a side-opening style, start by fastening the predator baffle in a fixed position with nails or screws. Come through the floor and the opposite side. This strengthens the nest box. Next, place two 3 in. (7.6 cm) strap hinges at the bottom corners of one side (A). To close and secure, place screws at the two upper corners (B). Or use two spring-loaded eye bolts (screen door hooks with a safety latch). You may prefer using two galvanized nails placed at a slant. For extra security, please place a screw through the movable side at C into the predator baffle. Allow about 3/8 in. (1.0 cm) clearance along the top.

The side-opening style is easier to clean than the rear-opening type and the entire box can be easily inspected. If you have large hands, you will no longer scrape them on the inside of the box. The possibility for premature fledging may exist and it is more difficult to trap and remove House Sparrows from a side opening box. When trapping sparrows in this style box, place a clear plastic bag over the entire box to prevent the sparrow's escape.

1040 Maricopa Dr.
Oshkosh, WI 54904