SCOTT SHALAWAY Making nest boxes baffling

Tis the season to build, repair and clean nest boxes for cavity-nesters such as bluebirds, chickadees, and tree swallows. This is one of my favorite chores because nothing brings more satisfaction than seeing a pair of cavity-nesters using a nest box.
Unfortunately, over time nest success often plummets to near zero. Raccoons, feral cats, and rat snakes remember nest box locations and return repeatedly for easy meals. Nest boxes become predator feeders. And nothing discourages an enthusiastic backyard birder more quickly than losing a nest full of eggs or chicks. Fortunately, there are several ways to significantly reduce predation.
First step: The first step is to understand the predators that cause the problem. Raccoons and climbing snakes are the most serious nest box predators, though cats, chipmunks, and squirrels take their fair share when they're abundant in an area.
Because these predators are all excellent climbers, tree-mounted nest boxes usually become death traps. Even if the trunk is wrapped with sheet metal below the nest box, predators have easy access from above. So at the very least, nest boxes should be mounted on free-standing poles.
However, while nest boxes mounted on metal poles may seem safe, most predators climb such poles easily. Coating the pole with a thick layer of axle grease sometimes discourages snakes because it fouls their scales, but mammals often tolerate the mess and persist until they reach the nest box. An easy meal is apparently worth a messy fur coat.
Baffle them: The best way to reduce predation at nest boxes is to "baffle" the boxes. A baffle is a sheet metal or PVC barrier hung just below the box to prevent climbing predators from reaching the nest. It may take the shape of a large shallow, inverted cone or it may be an eight-inch diameter cylinder. The cone should be at least 36 inches in diameter; the cylinder should be at least 24 inches tall. When baffling nest boxes, bigger is better.
Both styles of baffles are readily available commercially at wild bird stores and garden centers. If you just need a few baffles, buying them is easier than making them. If you've got lots of nest boxes to protect, however, making your own is cheaper.
To build a shallow cone, cut a 36-inch diameter piece of sheet metal and make a hole in the center large enough to accommodate the mounting pole. Then use tin snips to make a straight cut from the outer edge to the center. Pull the two free edges together so they overlap slightly and screw or rivet them together. The cone-shape results as the edges overlap.
A cylindrical baffle requires only a length of stove pipe and some half-inch hardware cloth.
Cut a circle of hardware cloth that's just a bit larger than the inside the diameter of the stove pipe. Then cut a small hole in the center of the wire mesh to accommodate the mounting pole and bend the edges of the hardware cloth downward so it fits snugly inside the pipe about an inch from the top.
Now cut three equally spaced, inch-wide, inch deep tabs around the top of the pipe. Bend these tabs down to secure the hardware cloth from above.
The support: Support either type baffle by bolting together two pieces of hanger irons on the pole just below the nest box. Baffles will wobble freely on this support piece and further discourage predators from even attempting to bypass the baffle.
If nest boxes are hung in the woods for chickadees, titmice, and nuthatches, baffles have limited value because access from above is so easy.
Consider this before starting a woodland nest box trail. In open bluebird habitat, however, baffles can reduce predation to almost zero.
I speak from experience. Eight years ago I baffled ten boxes that had previously been used, often unsuccessfully, by bluebirds or chickadees.
Since then, I've not lost a single nest in any of these boxes to raccoons or climbing snakes. I've concluded that fewer, successful nest boxes are better than more, predator-friendly ones.
sshalaway @aol.com