Fifty years ago I was up there too -- balancing on a shaky extension ladder checking my tree-mounted wood duck nest boxes. Over the years since then I’ve made about every mistake possible while managing wood ducks and boxes. My biggest mistake was hanging the boxes on trees, and as high as I could. Not good. In time, the talented squirrels, mink, and raccoons on my farm figured out that those odd rectangular things were either great nest sites (squirrels) or food shelves (mink and raccoons.) There is a better way for both humans and hens, and it does not involve either ladders or the wrapping of trees.

Background: Wood duck hens evolved to nest in natural tree cavities. A recent study showed that only about 20% of such nests successfully hatched. Failed nests and dead hens were mostly due to raccoon predation. While it seems natural to mount nest boxes on a tree, it is difficult to protect them from climbing predators. On the other hand, it’s simple to exclude these predators if the box is mounted on a pole and protected with an effective predator guard. Hens readily accept these set-ups, giving them a great chance to be successful. Studies have shown that hens actually prefer low-mounted boxes. Higher is NOT better.

The Method: The Wood Duck Society (WDS) has endorsed a Best Practices method of box mounting. It involves bolting a side-opening box to a pole, with the hole just six feet from the ground. A metal cone predator guard is placed below it. Walk-up monitoring! The photos at the bottom of this page show the method in action on jump day.

Material Sources: Cedar nest box kits (Helmeke design) are available from the Minnesota Waterfowl Association (MWA) at www.mnwaterfowl.com Cone predator guards and supporting brackets may be purchased through MWA’s Prairie Pothole chapter website at www.prairiepotholeday.com

History and Cone Rationale: This technique is not new. In 1958, a drawing illustrating a taller version of this method appeared in a U.S. Fish & Wildlife bulletin written by Clark Webster. Bellrose and Holm, in their classic text, Ecology and Management of the Wood Duck, stated: “When constructed to the proper dimensions and snugly fitted, cone shields provide the best available protection against pole-climbing predators [including rat snakes and their kin].”  No predator guard is 100% effective, but the cone comes close. Bears remain unimpressed, and small avian egg predators (woodpeckers) are not deterred. On my 100 box unit in Minnesota, loaded with raccoons, mink, and squirrels, I shifted in desperation to this technique over 30 years ago. The mammalian predation rate plummeted to zero and it has stayed there. Effectiveness did not change when I lowered the box to six feet and added side doors to allow walk-up monitoring.

Adding a cone guard to a pole is easy. With practice a cone can be attached to a pole in ten minutes flat. Dangling PVC pipe guards on overwater poles will deter swimming predators but have been unreliable for me on land-based poles. Squirrels have usually been the first to figure out that they can scramble up a PVC pipe after it loses its initial sheen. Overwater poles eliminate the squirrel, but not the need to deal with boats, waders, changing water levels, and ice-out pole-bending.

Poles and construction details: Eight-foot treated landscape timbers, flat on two sides, work well and are cheap. Using a post hole digger, carve a hole two feet deep. Place pole, then tamp dirt firmly around its base. You now have a “tree” right where you want it. Bolt the box to the pole so the entrance hole is six feet from the ground. If discarded stop sign poles are available from the local highway department, pole placement is even easier and can be done in wet areas. Bolt two 40 degree angled support brackets (use lock washers) to the pole below the box, then wrap a three foot diameter sheet metal cone guard over them. The lip of the cone should be at least three feet from the ground. A Vise-Grip pliers will hold the overlapped edges of the cone in position. Using a portable drill, affix small carriage bolts or screws through both edges. Then bolt cone (lock washers) to the brackets. Paint the cone an earth-tone color.

Placement: Ideally, choose a site near a wooded area and close to a clean wetland with a strong aquatic insect population. Both the egg-laying hen and her ducklings require a diet rich in aquatic invertebrates. Face the hole toward flight lanes or an adjacent wetland. If you live near good habitat, angle the box  so you can see part of the hole from your breakfast window. Squirrels can leap eight feet horizontally from tree trunks, and drop eleven feet from overhanging limbs, so plan accordingly.

Heat: Pole-mounted boxes are seldom in complete shade. Boxes made of metal, insulated plastic, and even plywood, when exposed to direct sunlight on hot June days, can become way too hot for the hen and her eggs. White paint and vent holes help, but it’s better to choose boxes built with natural wood. Wooden boxes have been shown to be the best at resisting heat build-up.

Teaching Bonus: By using the Best Practices mounting method, a youngster can not only help construct a box, but can also safely participate in placing and monitoring it. Watch for the smiles when small children climb on top of a five gallon pail and find out they are nose to nose with (and can touch) a growing clutch of eggs.