Wood ducks are cavity nesters
Every spring throughout Minnesota where suitable wood duck habitat exists, wood ducks, or woodies as they are also called, are busy seeking breeding and nesting sites in order to rear their young. What sets them apart from so many other ducks is the fact that this duck, unlike most species of waterfowl, chooses holes inside of trees for nesting rather than on the ground. Wood ducks are bona fide cavity nesters.
Needless to say, trees are essential not only as sources of food such as acorns from oaks, but most importantly for nesting. Natural occurring cavities, or those excavated by woodpeckers and other species of wildlife, are critical for wood duck survival. Without appropriate and abundant cavities, the wood duck would not have evolved as it has.
It was the lack of cavities from uncontrolled logging activities and development, as well as unregulated hunting, which led to the near extinction of the wood duck in the late 19th and early 20th centuries. Today, thanks to forestry management practices that consider the needs of wildlife as well as regulated hunting seasons to restrict harvest, the wood duck is now one of the most plentiful species of waterfowl in North America.
Furthermore, the construction and placement of tens of thousands of human-made artificial nest boxes by conservation minded citizens, organizations, and natural resource agencies throughout the wood duck's breeding range has helped to achieve an important wildlife recovery.
Like building bluebird houses and other wildlife nest boxes, constructing wood duck houses, placing them on trees or posts, and monitoring them has proven to be a hobby that benefits both humans, woodies, and other ducks. Hooded mergansers, common mergansers, buffleheads, and common golden-eyes are other species of waterfowl that readily accept artificial nest boxes for nesting.
We humans benefit from the satisfaction of contributing to wood duck conservation. A well-made structure placed on a tree or pole where wood ducks inhabit is a practice that often leads to a lifelong addiction. During my days managing the Wetlands, Pines and Prairie Audubon Sanctuary, I built and installed many wood duck houses around the refuge's abundant wetlands.
By late winter and very early spring, just before the arrival of the first pair of woodies, cleaning out the nest boxes provides an opportunity to take stock of the condition of the structures and to assess suitable sites for new boxes. So far this year I have added one more nest box to my assortment that now numbers 17 surrounding Lake Assawa near my home.
My annual check of each box usually reveals some interesting discoveries. A couple of weeks ago when I made the rounds in my snowshoes lugging a ladder and pulling a sled of supplies, I discovered that most boxes were stuffed with gray squirrel nests. Two boxes contained a dozen or so unhatched eggs of hooded mergansers, but four others held egg membranes and shell fragments belonging to wood ducks, which is a good sign of successful hatches.
One box housed nesting kestrels last summer, while another was currently occupied by a whole family of flying squirrels. A few other boxes appeared to have had no visitors or occupants at all, and one box was used by a starling. Nevertheless, each "wood duck" house was cleaned of old nest debris (except for the flying squirrel home) and a four-inch bed of fresh new wood shavings placed inside.
Now that all of my wood duck houses have been cleaned, all I can do now is wait to see who comes. Female wood ducks will soon be searching for suitable cavities. Once courting and breeding is completed, one egg per day will be laid until ten to 15 eggs have accumulated in the bottom of the nest cavity or nest box. After an incubation period of about a month, the ducklings will hatch and remain inside the cavity for about a day.
Then, implausibly, each duckling climbs out of the cavity or nest box and leaps courageously to the forest floor or wetland below. Vocalizations from their mother, coupled with a strong desire to leave the nest and begin feeding, helps encourage each duckling's departure
Moreover, fluffy down feathers help to soften the impact, and webbed feet act as parachutes to slow their descent. When all the ducklings have safely joined the hen, she leads them to a nearby brooding pond where the youngsters soon learn how to chase and capture insects and forage for other goodies.
Wood ducks are just one of the reasons why wildlife managers encourage private landowners to leave dead trees to remain standing, especially when located near wetlands in prime wood duck nesting habitat. In the Midwest, some 26 species of mammals and 43 species of birds use snags as nesting and perching sites. Snags are also used as food sources and for territorial purposes.
The cavity nesting wood duck are returning to the northland. Leaving for warmer climates each and every autumn, but returning in early spring, their presence in the trees, our nest boxes, wetlands and rivers is yet another reason to get out and enjoy the great outdoors.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at email@example.com