Arguably, the male wood duck (figure 1) is the most beautiful duck. Wood duck is the only wild duck species that frequently nests in southern Oklahoma and northern Texas. Nesting efforts by a few other duck species, such as hooded merganser and mallard, have been documented in this area, but are rare. Wood duck is one of the approximately eight duck species that nest in trees in the United States — it nests in cavities inside trees. Most waterfowl species nest on the ground.
Wood duck populations decreased during the late 19th and early 20th centuries as wetlands were drained and forests were cleared, especially old growth riparian forests containing many mature trees with nesting cavities. Since the late 1940s, people have intensively studied wood ducks looking for ways to help increase their populations. We have learned that wood ducks readily adapt to nest boxes (figure 2), which is surely advantageous because it takes 150-200 years to grow an old growth riparian forest. Thousands of wood duck nest boxes have been erected during the last 50 years and wetland protection and construction have expanded during the last 35 years. Wood duck breeding populations responded by increasing at an overall continental rate of 5.9 percent per year during 1966-1999.
However, wood duck populations did not increase everywhere. Unfortunately, breeding wood duck populations appear to be declining in several portions of Oklahoma and Texas. At least 85 percent of the riparian woodlands have been eliminated or degraded in these areas.
What can we do to help produce more of this fascinating and beautiful duck? Maintain or develop wetlands and manage wood duck nest boxes. An ideal wetland for raising wood ducks has flooded shrubs and trees, such as buttonbush and black willow, substantial herbaceous emergent and floating aquatic vegetation, open water, and at least 10 acres of surface area with most of the area less than three feet deep. Shrubs and aquatic vegetation should dominate more than 50 percent of the wetland while open water should comprise less than 50 percent. A collection of smaller wetlands can serve this function if their combined area exceeds 10 acres and they are joined by water channels, or separated by less than 50 yards of land. It is best that such wetlands not have many bass larger than one pound because bass eat small ducklings.
The best location to place wood duck nest boxes is in such wetlands. Placing nest boxes in subpar habitat probably harms wood ducks more than it benefits them, even when they successfully hatch broods. Wood duck hatchlings climb to the nest entrance, jump out of the nest, and begin following the hen within the first 24 hours after hatching. Wood ducks sometimes use nest boxes erected some distance from water, but then have to walk the ducklings to an appropriate wetland. Duckling mortality increases as the distance increases that they travel over land.
A good design for wood duck nest boxes is shown in figure 3. Bald cypress wood or three-quarter-inch exterior plywood probably are the best choices for nest box materials. Although less durable, nest boxes can also be made of pine, cedar, or spruce. The most durable material probably is metal, such as galvanized steel. Wood or plastic nest boxes can be purchased from commercial sources. Initially, wood boxes are more readily accepted by wood ducks than metal or plastic nest boxes, but after artificial nest boxes have been used well by wood ducks for a while at a site, all should be accepted. Metal and plastic nest boxes should be placed in locations that are shaded during the afternoon to prevent excessive temperatures in the boxes. Hardware cloth should be attached to the inside of metal, plastic, and smooth wood boxes between the floor and entrance hole so the ducklings can climb out of the boxes.
Wood duck nest boxes should be erected prior to March 1. Nest boxes should be placed at least four feet above flood level. Entrance holes should be oriented toward an open area providing an unobstructed flight path. About three to four inches of nesting material, such as wood chips or sawdust, should be placed in the bottoms of the boxes. The boxes should not be placed close to or under overhanging limbs, which could provide easy access for predators. Metal cone predator guards (figure 2) should be placed on the supporting pole under the boxes to prevent rat snakes, raccoons, and squirrels from eating the eggs (a February 1997 NF Ag News and Views article addressed such predator guards). Nest boxes should be checked each winter, and, if necessary, repaired. If European starlings (a non-native urban and agricultural pest that is a nest competitor) try to nest in the boxes, nest boxes should be checked weekly during April through July to remove starling and paper wasp nests. It is a good idea anyway to check the boxes weekly to monitor wood duck utilization and nesting success. Other desirable native birds sometimes nest in the boxes such as screech owl, great-crested flycatcher, and hooded merganser.