Ducks are not usually the first birds considered when thinking about bird houses, but there are many cavity-nesting ducks that appreciate duck boxes. By providing appropriate boxes in the right habitat, birders can help increase duck nesting territories, and backyard birders who have a suitable pond may even be able to attract nesting ducks to a good box.

Ducks That Use Houses

Not all ducks will nest in boxes, but a surprising number of duck species are cavity-nesters and will use old woodpecker holes, large decayed snags and other nesting sites, as well as boxes.

Ducks that readily nest in suitable boxes include:

• Barrow's goldeneye
• Black-bellied whistling-duck
• Bufflehead
• Common goldeneye
• Common merganser
• Hooded merganser
• Mandarin duck
• Muscovy duck
• Wood duck

While the exact type of house each duck prefers will vary, they are quite adaptable to different house styles and sizes, particularly if other natural cavities are less widely available. In many cases, ducks will nest more frequently in boxes as ongoing development destroys more habitat and nesting sites become scarce.

Duck Box Dimensions

Because ducks are much larger than typical birds that use houses, the best boxes for ducks are also noticeably larger. Larger boxes can also accommodate larger broods, since female ducks will often lay eggs in nests other than their own, and the brooding female will adopt those foster ducklings. A safe, comfortable box will be able to house all those chicks without difficulty.

• Entrance Hole: Entrance holes for duck boxes are often oval-shaped to accommodate ducks' larger size and longer bills, and proper entrance hole sizes range from 3-3.5 inches tall by 4-4.5 inches wide. Rectangular holes are also common on duck nesting boxes. Many times such large entrances are protected with small tunnels to discourage predators.
   

• Entrance Height: While the height above the floor will vary depending on the overall height of a duck box, the entrance is usually positioned 3-6 inches below the top of the house. A slight overhang from the roof will help protect the entrance from excessive moisture and sunlight. A ramp might lead to the entrance to help ducks enter and leave, but it is not necessary.
   
• Interior Floor Space: The interior floor of a duck box must be sizeable enough to accommodate a large brood, yet small enough to keep them cozy since many cavity-nesting ducks use little or no nesting material to protect and cushion their chicks. Floors on duck boxes are usually 7x9 inches or 8x10 inches. No matter what size, the floor should have appropriate drainage.
   
• Total House Height: Because ducks are larger birds, a taller house can help keep them safe. Depending on the species, a box may range from 18-25 inches tall, with the rear wall generally 2-3 inches taller than the front to allow water to easily shed off a slanted roof. Inside the box, the walls should have thin grooves or have hardware cloth or mesh attached so ducklings can climb out when they are ready to leave.

Duck Box Placement

Proper placement is critical for a duck box to appeal to interested residents. Ideally, the box should be placed on a sturdy pole over the water, well above the highest reach of the water – this will prevent predators from easily accessing the house, and provides a soft landing for altricial ducklings when they leave the nest. If a water placement is not possible, positioning the house no more than 150-200 yards from a good water source such as a marsh, lake or pond is suitable. The entrance should face the water but be protected from prevailing winds, and if necessary, nearby limbs or branches can be slightly trimmed to allow adult ducks an easy flight path into the house. The box should be placed 4-15 feet above the ground, and baffles, cones or other deterrents should be in place to protect the house from predators.

Tips for Duck Boxes

It can take ducks several seasons to discover an appropriate house and feel comfortable using it. To keep the house suitable each year…

• Check the house regularly for necessary repairs or adjustments.
• Add a thick layer of wood chips, straw or sawdust to serve as nesting material.
• Clean boxes in late fall or early winter and again in spring so they are ready for residents.
• Monitor boxes if necessary and investigate the possibility of banding ducklings.

Ducks aren't the first birds most birders think of when they think of bird houses, but duck boxes can be welcome additions for many nesting ducks, and when ducks do use a house, birders can enjoy the experience of being landlords and monitors for these wonderful waterfowl.

Photo – Mandarin Ducks at a Nest Box © Gidzy