Wood ducks depend on two things people were removing at once: mature trees with cavities, and freedom from year-round shooting. Logging of bottomland hardwood forest destroyed nest sites while unregulated market hunting took adults, and by the turn of the twentieth century the species had vanished from much of its former range.
The Migratory Bird Treaty Act of 1918 closed the hunting season, and the population began to recover. From the 1930s onward, wildlife agencies and volunteers added nest boxes by the hundreds of thousands, giving the birds cavities where old trees had gone. The wood duck is now among the most common breeding ducks in eastern North America and again supports a regulated hunting season.
One complication of the box programme is dump nesting, where several females lay in the same cavity. Clutches of dozens of eggs can result, and hatching success falls. Box designs and spacing are adjusted to reduce it, but how much boxes rather than habitat recovery drove the rebound is still argued.