Safe an Effective Housing for Cavity Nesting Waterfowl

By Wildlife Biologist Allen Starr

As we have discussed in previous posts, providing nesting boxes for waterfowl can be a worthy and beneficial program to increase cavity nesting waterfowl production.  Placement of boxes and protection from predators are essential practices for a successful nest box program.  Enfield Regional Biologists, over the past several years, have been upgrading some of our nest box areas to increase use by waterfowl, nesting success and to reduce predation on nesting waterfowl.

One nest box area, that we inherited from a volunteer group that no longer could conduct the required yearly maintenance, had older nest boxes that had been installed on shoreline trees.  Some boxes were on islands in the flowage and others were on the shore of the flowage.  When conducting checks in the spring and during winter maintenance, we observed that the existing boxes were receiving little or no use and predation was evident (mostly by raccoons but fisher will also target nest boxes).  Gradually, we began removing the shoreline boxes and installing new ones on cedar or U-channel posts over two to four feet of water.  This takes considerable effort (transporting posts, boxes, etc.) by snowmobile, drilling holes through the ice with an auger and then driving the posts into the flowage bottom with a sledge hammer.  But, the extra effort was well worth it.  Checks the following spring showed increased use in the new boxes over water.  We continued removing shoreline boxes and installing new ones over water over the next several years.  Subsequent checks over the following years yielded significantly higher use by waterfowl and greater hatching success.  Successful hatching of ducklings can be determined by the detached shell membranes that are left behind in the box.  Even though these boxes were installed over water with sheet metal on the post as a predator guard, we were still having some problems with predation.

Our next objective was to reduce the incidence of predation in our boxes.  This can be difficult because once a predator realizes there’s a free meal to be had, they will continue to visit the box either to catch the duck or have a raw, scrambled egg breakfast!  The solution was a new and improved predator guard.  These cone-shaped, metal guards prevent the predator from shimmying up the post and gaining access to the box.  There are metal supports under the guards to provide support, but when a predator tries to climb on them they tilt and the thief ends up in the water.  Cone predator guards are available commercially or can be constructed using plans available online such as:  http://www.sialis.org/conical.htm. 

Placing nest boxes over water and installing effective predator guards may not stop 100% of predator problems with your nest boxes, but give it a try.  Undertaking this additional effort should increase use by waterfowl, increase hatching success and decrease predation problems with any nest box program, whether it’s a few boxes or a large operation.  For additional information about starting and maintaining a waterfowl nest box program contact your area Regional Wildlife Office.