Of the many species of ducks in the world, only two have been successfully domesticated: the mallard and Muscovy ducks. If you have mallard ducks, they tend to nest on the ground and so won't need much help building nests. Mallards will use nest boxes if they are specifically designed and placed, or if they were raised in one. Muscovy ducks are known as cavity nesters, meaning they nest in holes and do not know how to build nests for themselves. If you have a Muscovy duck or ducks, you will need to build a box for them to adopt as their home.
Using a measuring tape, straight edge and pencil, measure and number your wood into six pieces according to the following measurements and cut with a handsaw or tablesaw:
One piece measuring 31 by 9.25 inches, numbered "1." This will be the back of the box.
Three pieces measuring 23.5 by 9.25 inches, numbered "2," "4" and "5." These pieces make up the side (2), front (4) and door (5).
One piece measuring 7.75 by 9.25 inches, numbered "3." This is the floor.
One piece measuring 14 by 9.25 inches, numbered "6." This is the roof.
Attach the side piece (piece 2) to the left side of the back (piece 1), flush with the edge and leaving an equal amount of space above and below the side piece. Use four screws and fasten them from the back of the box (piece 1) in a vertical line down the edge of the side (piece 2).
Drill five evenly spaced holes in the floor (piece 3) using a 1/2 inch drill bit. Attach this piece using four screws. Fasten two through the back (piece 1) and two through the side (piece 2)
Draw an entry hole on the front of the front piece (piece 4). Place the hole 3.25 inches from the top edge of the piece and centre it carefully. Be sure to make the hole and oval shape large enough for your particular breed of duck to fit through. Drill a pilot hole and then cut out the hole using a jigsaw.
One the inside face of the front piece (piece 4), use a saw to make horizontal lines from just below the entry hole to the bottom. These will provide toeholds so that any ducklings can climb out. Attach the piece using six screws, four down the left edge attaching to side (piece 2), and two across the bottom attaching to the floor (piece 3).
Round off the top, outside edge of the door (piece 5) using sandpaper. Since this is the door, it will hinge open so bedding can be added and removed. Attach the door (piece 5) using one screw from the front (piece 4) and one from the back (piece 1). These screws form the hinge so don't fasten them too tightly, or the door won't open.
Attach the roof (piece 6) using seven screws. Fasten three screws from the back (piece 1), two screws into the side (piece 2) and two screws into the front (piece 4).
Fill the nest box with a 4-inch to 6-inch inch layer of wood shavings and attach it to a wooden post or tree stump -- whatever you are using to mount the box. Attach the box by fastening screws through the extra space at the top and bottom of the back piece.
Always mount the nest box so that it faces the water. Boxes should be placed above seasonal high water levels, usually four to six feet above the ground, though you can place them lower if the water level in your duck's living area does not get that high. If your ducks have their wings clipped, you can build a ramp up to the nest box. If you do this, make sure their living area is safe from predators who might use it to get into the box.
If building more than one nest box, never mount them back to back. Place the boxes a good distance apart so ducks won't compete for nesting space. Avoid using straw or hay as bedding as it can get damp and develop mould, which will cause disease. Do not use sawdust for bedding as young duckling can suffocate in it. Do not use finished wood, and do not apply finish to the inside of the box as the chemicals are toxic to ducks.