Northern Prairie Wildlife Research Center
The following plan (Figure 16) shows how to construct a cone-shaped, sheet-metal guard for protecting nest structures from predators. The diagram shows how to cut three predator guards from a 3-foot x 8-foot sheet of 26-gauge galvanized metal.
When installing the guard, overlap the cut edge to the dotted line. The sequence of numbers on the solid lines is provided to facilitate cutting. Make circular cuts in a counter clockwise direction. The initial cut on line A-B can be started by making a slot at A with a chisel. Then proceed with a tinsnips. Be sure to wear gloves.
These cone-shaped predator guards work best on trees or wooden poles with a trunk diameter of up to 6 inches. As is shown in the plan, the cone-shaped predator guard is secured to the pole or tree with wooden mounting blocks and galvanized nails. The lower edge of the cone should be at least 36 inches above the ground or water.
Trees with a diameter over 6 inches can be guarded with a 33-inch band of sheet metal about 3 feet high which completely encircles the trunk. This type of guard can be attached with a nail and flat washer at appropriate places on the overlap. The band should be loose enough to allow for growth of the tree. This "wrap-around" type of predator guard is an option that can be used on any size tree and wood or metal support poles (Figure 17).