By Johann Walker, Ph.D.
One of the most crucial times in a duck's life is the period between hatching and fledging. Research tells us that duckling survival is a close second to nesting success as the most important factor influencing the size of duck populations. Although brood ecology is not as well studied as nesting success or adult survival, we've learned that ducklings rely on a combination of camouflage, clever behavior, quality habitat, their mother's vigilant care, and a little luck to survive a multitude of dangers before fledging in mid- to late summer.
A duck's life story actually begins before it hatches from the egg. A nesting hen lays about one egg per day until her clutch is complete, and she will incubate her eggs for about a month after the last egg is laid. Despite differences in the ages of her eggs, which can vary by as much as 10 days or more depending on the size of the clutch, all of them typically hatch within a 12-hour period. Remarkably, ducklings know when it's time to hatch by communicating with each other while still inside the egg. Toward the end of incubation, developing ducklings begin making a range of subtle sounds, called "pipping."
This ensures that the ducklings will hatch at approximately the same time, and that none of them will get left behind.
Ducklings use a pointed bump on the end of their bill, known as an "egg tooth," to crack open their shells. The ducklings hatch with a full set of feathers and open eyes. The hen keeps her brood warm and dry by covering them with her body and wings. Once the ducklings' fuzzy down has dried they are ready to leave the nest. Unlike songbird hatchlings, which remain in the nest while they are fed by their parents, ducklings can feed on their own. They can also swim and dive. Within 24 to 48 hours after the ducklings hatch, the hen leads them to a nearby wetland to feed.
Duckling mortality is highest during the first two weeks after hatching, when the tiny down-covered birds are most vulnerable. During this time, ducklings are extremely secretive, relying on the natural camouflage of their down feathers and on wetland vegetation to conceal them from predators. They also depend on their mother to keep them warm in inclement weather, to lead them to good hiding places, and to distract predators that threaten them. Despite the best efforts of attentive hens, many ducklings die from exposure in cold, wet weather or are claimed by a variety of predators, including raptors such as great-horned owls and small mammals like mink.
Research indicates that brood habitat quality plays an important role in how many ducklings survive to fledge. In the Prairie Pothole Region, landscapes with numerous small, shallow wetlands are associated with increased duckling survival. These seasonally flooded ponds teem with high-protein aquatic invertebrates, which provide ducklings with the nutrients they need to grow quickly, and contain thick emergent vegetation that helps protect broods from predators and inclement weather. Throughout the brood-rearing period, hens and their ducklings often move several times overland between neighboring wetlands in search of ideal habitat for feeding and growth.
If ducklings make it through the first two weeks of life, they have much better odds of surviving to become full-fledged members of the fall flight. During weeks three through six, they lose their fuzzy down, and their contour feathers begin to develop. As ducklings grow, they are better able to maintain their body temperature and escape predators by diving and skittering away. Older ducklings are less secretive and can occasionally be seen in open water, especially during the morning and evening hours. They spend most of their time feeding, chasing low-flying insects, and tipping and diving for submerged aquatic invertebrates.
By the time ducklings are seven to eight weeks old, typically in late August or early September, they are almost full grown and look very similar to adult birds in eclipse plumage. Their wing feathers are fully developed, and the ducklings are capable of making short flights around the marsh. As the days grow shorter and the nights colder, the young ducks become restless and begin making longer exploratory flights away from their natal wetlands. During these forays, broods mix with other ducks in the area and join larger flocks as they prepare for migration. On the prairies, mallards and pintails gather in impressive flocks as young-of-the-year and adult birds begin feeding together in harvested grainfields. At this point, the young birds that began life only a few months before as tiny fuzzballs are ready to begin their long journey south to their wintering grounds. With luck, many first-year hens will return to the breeding grounds the next spring with mates and will raise broods of their own.
As in all stages of the annual cycle of waterfowl, the key to the well-being and survival of duck broods is healthy and abundant wetland habitat. Even in the best of circumstances, ducklings live in a dangerous world, but on significantly altered landscapes where brood-rearing habitat is limited, duckling mortality increases dramatically. In the Prairie Pothole Region, the most productive landscapes for broods are those with high densities of shallow, seasonally flooded wetlands. Without these habitats, few ducklings would survive to fledge. Tragically, seasonal wetlands continue to be drained and degraded at a staggering rate across the prairies. Ducks Unlimited is working hard to save these threatened habitats—and sustain healthy waterfowl populations—through the Preserve Our Prairies Initiative. To learn more about how you can help conserve wetlands and other crucial waterfowl breeding habitat on the prairies and in other high-priority areas, visit the DU website at ducks.org/DUinitiatives.
Dr. Johann Walker is DU's director of conservation programs in North Dakota, South Dakota, and Montana.