The Wood Duck (Aix sponsa) is perhaps the most brightly colored waterfowl in North America, with the male displaying a striking iridescent pattern of greens, blues, and purples. Unlike most other ducks that build nests on the ground among dense vegetation, the Wood Duck is a cavity nester. This means the female seeks out hollow spaces high above the ground in trees. The Wood Duck’s reliance on tree cavities has shaped its habitat preferences and led to innovative conservation efforts to ensure its successful nesting.
Natural Tree Cavity Selection
Wood Ducks naturally select nesting sites in mature or decaying trees within wooded wetlands, swamps, or bottomland forests, typically near slow-moving or still water. The proximity to water is important, although a hen may choose a cavity up to a mile away from the nearest pond or stream if suitable trees are scarce.
The female duck cannot excavate her own hole, so she relies on naturally occurring hollows in large, mature trees, often with a diameter greater than one foot. These cavities form where a branch has broken off and the heartwood has begun to rot, or they may be old, enlarged holes made by large woodpeckers. The height of the nest can vary widely, but higher sites are often preferred for safety.
The entrance hole to the cavity is a critical detail, as a small opening makes it harder for predators like raccoons to enter. Preferred entrances can be as small as four inches across. Once the female selects a cavity, she brings in little nesting material, instead using existing wood chips or debris at the bottom of the hollow. She will then line the nest bowl with soft down feathers plucked from her own breast just before she begins laying eggs.
Installing Artificial Nesting Sites
The destruction of wooded wetlands and the clearing of mature forests have led to a shortage of natural cavities, making artificial nest boxes a major factor in the Wood Duck’s population recovery. Providing a sturdy, well-placed nest box can offer a safe alternative to a natural tree hollow. These wooden boxes are typically mounted on poles over the water or on trees near the water’s edge, creating a secure environment.
Proper placement is key. Boxes should be mounted between six and 12 feet off the ground, or at least three feet above the high-water mark if placed directly over water. Mounting the box on a metal pole with a cone-shaped predator guard is the best practice, as this prevents climbing predators like raccoons and snakes from accessing the nest. The entrance hole should face the water, and the flight path to the box needs to be unobstructed.
The interior of the nest box requires three to four inches of wood shavings or coarse sawdust, as the hen does not carry in this initial material. This bedding cushions the eggs and insulates the clutch during incubation. Additionally, the inside of the front panel must have a rough surface, often achieved with hardware cloth or grooves, which provides a ladder for the ducklings to climb to the exit hole. Nest boxes should be checked and cleaned out annually, with fresh shavings added before the start of the next nesting season, typically in late winter or early spring.
The Ducklings’ Descent and Departure
The most dramatic moment in the Wood Duck’s nesting cycle is the ducklings’ departure, a remarkable event that occurs very soon after hatching. Within 24 hours of emerging from their shells, the newly hatched ducklings prepare to leave the nest cavity. The female descends to the ground or water below the nest and begins a soft, persistent vocalization that encourages the young to exit.
The ducklings, which are fully coated in down and immediately mobile, respond to their mother’s calls by climbing the rough interior of the cavity or the provided ladder. One by one, they launch themselves out of the entrance hole, free-falling to the ground or water below, a distance that can be 50 feet or more. Their light weight and soft down allow them to survive the drop without injury.
Once they land, the ducklings quickly gather around the hen. She then leads the entire brood away from the nest site toward protective cover on the water. They will never return to the nesting cavity after this initial descent. The female will guide her young to dense aquatic vegetation where they can immediately begin foraging for the small insects necessary for their rapid growth.