By J. Brian Davis, Ph.D.
The sight of a brood of day-old ducklings in spring is guaranteed to raise a smile on anyone's face. The downy little puffballs seem the epitome of innocence, and their daily routine appears endearingly simple: scamper after a few insects and, above all, keep up with the rest of the brood. But the lives of ducklings and goslings are not as easy and carefree as a casual observer might think. Young waterfowl face many obstacles early in life. The timing of hatch, local abundance and quality of wetlands, weather, predation and other factors impact the survival of ducklings and goslings.
The mating strategies of ducks and geese are an important influence on how many young are produced. Geese have longer life spans than ducks and establish long-term pair bonds. Both parents look after the young, and survival rates for goslings are higher than those for ducklings. Ducks have shorter life spans, and most species select new mates each year. Among most North American duck species, only females look after the young (whistling ducks and, to a lesser extent, ruddy ducks are exceptions). For these and other reasons, geese generally hatch fewer offspring than ducks—two to seven goslings compared to seven to 12 ducklings, but additional parental care results in higher survival of individual young.
That young ducklings and goslings are self-feeding is another important factor contributing to their survival rate. Everyone has seen baby songbirds in the nest with eyes closed and mouths open. The adults of common backyard birds have to feed their young. Ducklings and goslings, on the other hand, hatch with their eyes open and already have feathers because they will soon have to feed themselves. Remarkably, young waterfowl spend only about a day in the nest. This is why the yolk of waterfowl eggs is so rich—it is a crucial energy source for the little birds during the first few days of life.
Waterfowl and other birds nest in spring because great quantities of food are available when their young hatch. Insects like midges and damselflies swarm the prairie skies, while beetles, fairy shrimp, water fleas and snails abound in the water. Young waterfowl gorge themselves on larvae or adult insects by rapidly skimming the surface of the water or by plucking the tiny morsels from wetland plants. Goslings in the Arctic forage on grasses and sedges, and also capture bugs on dry ground. Some waterfowl often nest more than a mile from water, so sometimes the little birds have to waddle a long way across dry ground before reaching wetlands. Adult waterfowl commonly lead their broods to many different wetlands, sometimes separated by hundreds of yards, or even miles, to find food and cover.
Why do young waterfowl select certain foods? Insects and some plants are loaded with protein. For the first two weeks of life, young waterfowl feed aggressively on such items because large amounts of protein are needed to grow animal tissue and feathers, which are at least 85 percent protein. Ducklings may spend 60 percent or more of each day feeding, especially during early morning and evening. Very shallow and weedy seasonal wetlands as well as deeper cattail marshes are important to broods for food and escape cover. During drought years, waterfowl are mostly dependent on the larger, deeper wetlands to fulfill their needs. Thus, dynamic wetlands, like those in the Prairie Pothole Region, are crucial for waterfowl and other wildlife. Young waterfowl lucky enough to survive gain flight in about 55 days, but this varies by species and other factors.
To maintain healthy waterfowl populations, two factors are especially important—nest success and survival of the young. Nest success and duckling or gosling survival strongly influence recruitment, which is the number of young that survive to breed the following spring.
Waterfowl recruitment is usually very good in wet years on the prairies like the 1970s and mid-1990s, and often decreases during drought years like the 1980s and early 2000s. When weather and habitat conditions are excellent, hens may renest several times if their earlier nesting attempts are unsuccessful because ideal wetland conditions assure excellent food supplies for ducklings. In dry years, wetlands are much less productive. As a result, hens nest less aggressively and produce fewer young. During these years, even ducklings that successfully hatch have lower survival because of reduced food supplies and more frequent movements between wetlands in search of food.
Likewise, duckling survival is highly variable and may be as low as 10 percent or higher than 70 percent. It seems that virtually any animal that is slightly larger than a duckling will eat it. In my research in the rivers and swamps of Mississippi and Alabama, I attached radio transmitters to nesting wood duck hens and their ducklings. I found that red-shouldered hawks, owls, fish, cottonmouths, snapping turtles, great blue herons and other predators ate about 300 of 435 radio-marked ducklings that I studied.
Besides predators, young waterfowl are sometimes exposed to harsh environmental conditions such as cold, rain and wind. Heavy rain, especially when accompanied by cold temperatures, can temporarily decrease the amount of insects available to ducklings. Inclement weather also compels the hen to increase brooding time to try to prevent the young birds from dying from hypothermia. For ducklings and goslings, more time spent brooding may mean less time available for feeding. Researchers in North Dakota have found that total loss of mallard broods may be five times more likely on days when it is raining than on days when it is dry.
Clearly, high-quality grasslands and wetlands are critical for nesting waterfowl and their broods. We cannot control droughts, but policies and management practices that promote large tracts of grassland and that prevent wetland drainage are vital for nesting success. Conserving these essential waterfowl breeding habitats is also the best way to ensure that the downy little birds hatched in spring will survive to wing their way south each autumn.
Dr. Brian Davis is a DU regional biologist based in Little Rock, Ark.