by John Coluccy, Ph.D.
Those of us who are parents have mixed memories of changing diapers and being awakened in the middle of the night by a screaming baby. But imagine yourself trying to look after four, eight or even a dozen babies all at once, and in a predator-filled environment. This is exactly the situation adult waterfowl face every year. As you can imagine, brood care among waterfowl is a daunting yet critical task.
Adult waterfowl provide their young with many types of care, and the investment in this care varies by species and even individuals. When they hatch, for example, most waterfowl are unable to thermoregulate (keep warm by automatically regulating their body temperature) for several days and periodically require a parent (the hen, in most duck species; both parents in the case of geese and swans) to cover them with their body and wings to help maintain normal body temperature. This behavior, known as brooding, also protects young waterfowl from extreme precipitation (including rain, hail and snow), sunlight, wind and from predators.
Another critical form of care is protection from predators. Most waterfowl utter alarm calls at the first sign of approaching danger. Alarm calls will either cause young birds to scatter, move closer to their parent(s), or freeze in place. Females of many duck species will also feign injury by acting like their wing is broken to draw predators away from their broods. Adult geese may actually attack intruders (including humans) who come too close to their offspring.
Another important role parent birds play is ensuring undisturbed access to feeding and loafing areas. After the young birds hatch, the parent(s) assist their young in finding suitable habitat with adequate food supplies. Sometimes, several broods will use the same wetland, however, and although females tend to avoid one another, contact among broods frequently occurs. In these instances, parents will aggressively defend the area immediately around their brood and attack individuals that come too close.
The majority of male ducks usually invest little or no energy in rearing offspring. In swans and geese, however, both parents are active participants in brood-rearing activities and may remain with their young until the following breeding season. Female geese and swans are typically emaciated following incubation because they feed infrequently during this period and, if left alone to care for offspring, they may be unable to provide sufficient care for young and meet their own requirements. By helping with brood care, males actually enhance the survival of their offspring and mates. The presence of both parents in swans and geese also helps fend off predators because most species of swans and geese nest in areas with little cover for concealment. A pair of adult swans or geese defending a brood is a formidable opponent for most predators.
In most northern-nesting ducks, on the other hand, males play little to no role in brood care. In fact, most male ducks abandon the female when she begins incubation or shortly after her eggs hatch. The bright plumage of the drakes may attract predators, so the male ducks rarely attend broods. Most female ducks usually remain with their broods until they are nearly on the wing. However, female ruddy ducks, diving ducks and sea ducks may remain with their broods for only a few days or weeks. Ducklings in these groups are well insulated and adapted to deep-water habitats; thus, they can avoid predators by swimming to open-water areas or by diving, and need little parental care.
Pair bonds of some southern-nesting ducks—mottled ducks and fulvous whistling ducks, in particular—are maintained throughout the year, and males of these species often attend females and broods. Long-term pair bonds may be beneficial because breeding and brood-rearing habitats are often favorable at irregular times of the year. The plumage of males resembles that of females in these species, so the presence of the male does not attract attention from predators.
Trying to successfully raise offspring in this world is a struggle for any parent. Considering the obstacles waterfowl face, I am extremely thankful for my only child and my wife. I hope, too, that my wife appreciates my sticking around to help in brood rearing.