Once a week for nearly a month, I checked the brand new nest box to see how the duck inside was faring. The wood duck hen had accepted the box in spite of its not-so-perfect construction. Its entrance hole, nearer to the center of the nest box's face, instead of closer to the top as it should be, evidently didn't sway the hen from selecting the structure and laying her eggs within the bed of fresh wood shavings. I was delighted that she was incubating her clutch inside the wood duck house my boy had built in school.
"A wood duck is using your nest box!" I announced to him one evening.
I had earlier walked by the oak tree that I had mounted the box onto and noticed her head and neck sticking out of the entrance hole. I quietly continued past the tree while acting as though I hadn't noticed her.
A few days later, I saw her exit the box, fly across the lake, and land - probably to feed. Seizing the opportunity, I quickly grabbed the ladder, propped it against the tree, climbed up, opened the top of the nest box and peeked inside. There, covered by a layer of feather-down plucked from her breast, was her entire clutch, 12 eggs in all.
"What a wonderful sight", I thought, as I climbed back down to the ground.
Wood ducks are indeed cavity nesters; that is, they routinely nest inside holes in trees, in addition to utilizing artificial nest boxes. Other species of waterfowl nest inside tree cavities and nest boxes too; buffleheads, common goldeneyes, common mergansers, and hooded mergansers are all North American cavity nesting ducks.
By the early 1900s, wood ducks were a species threatened by extinction. Unregulated hunting and habitat loss were reasons for their population decline. However, with timely legislation designed to protect migratory species -along with regulated hunting, habitat management and the placement of wood duck houses throughout the birds' breeding range - wood ducks are abundant once again.
Wood ducks are just one of the reasons why wildlife managers recommend leaving dead trees (snags) standing after a timber harvest, 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 for various reasons, including nesting and perching. Snags are also used as food sources and for territorial purposes. The best and most often-used snags are large hardwood trees, usually over 15 feet tall and at least 6 inches in diameter.
After a mated pair of wood ducks has selected a suitable cavity, a hen will begin to lay her eggs inside, one egg per day. Wood ducks do not gather nesting material like many birds do to build a nest. Rather, they rely on wood chips and debris commonly found inside natural cavities for their nest bowls. This is why it is recommended to add wood chips or shavings inside nest boxes.
The average clutch size is 10-12 eggs, but can vary from six-19. I once monitored a nest box in which a hen was incubating 21 eggs. Curiously, wood ducks will often lay eggs inside already occupied cavities for other hens to incubate. For this reason, it's advised to place wood duck houses out of sight from each other. Research suggests that boxes placed in plain view from one another encourages "dump nesting" among wood ducks.
After an incubation period of about a month, the ducklings hatch, spend about 24 hours inside the nest and then leap from the nest cavity to join their vocalizing mother waiting on the forest floor or nearby water. Once all the ducklings have left the nest, the hen will lead her brood to the water where they will immediately begin searching for food.
While many wood duck ducklings survive to fledge, migrate, and breed and nest the following year, most ducklings don't survive their first year of life. As well, there are untold numbers of ducklings that never get the chance to hatch inside the relative safety of a tree cavity or nest box.
Such was the case for the eggs of the wood duck hen that chose the nest box my boy had built. For, on a recent morning while anticipating that at any moment - maybe that very morn - I would discover either a nest of newly hatched ducklings or a scattering of egg membranes with a few bits of eggshell, a sure sign of a successfully hatched clutch of eggs, something much different had happened instead.
Nature's way isn't necessarily the stuff of happy storybook endings. As I approached the tree, I heard the hen wood duck calling from the nearby flooded sedge and emergent vegetation of the lake. I had hoped she was calling for her brood, but I suspected otherwise. I soon discovered that a predator of some sort, possibly a squirrel, had destroyed the nest and consumed many of the eggs.
Nevertheless, despite inevitable mortality, especially the unborn and newly hatched, more than 100,000 wood ducks breed in Minnesota each spring. Thanks to great strides in conservation and forestry and wildlife management, wood ducks are plentiful once again as we 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 firstname.lastname@example.org