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Nature or Nurture

Both instinct and learning play important roles in shaping waterfowl behavior
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By Tina Yerkes, Ph.D.

The apple doesn’t fall far from the tree. Unfortunately, I hear this all too often when my kids are misbehaving in public. Of course, I immediately attempt to blame their behavior on my husband’s side of the family.

In general, behavior develops because of the interaction between genetic and environmental influences, often referred to as the nature versus nurture debate. Genetically programmed, or instinctive, behavior is often associated with survival. For example, sucking is an instinctive behavior for a newborn baby and necessary for the child to survive.

On the other hand, some behaviors are learned, such as typing on a computer keyboard. Much research into the nature versus nurture debate has been conducted, including studies involving human twins, and scientists now accept that nature and nurture interact, which ruins my ability to blame my kids’ behavior on my husband’s family.

Imprinting is a good example of how both nature and nurture influence waterfowl behavior. Upon hatching, many waterfowl are genetically programmed to recognize and follow movement of any kind. During a short window of time, they are also capable of learning to recognize the first moving object they see and will become socially attached to it. This object is usually their mother. However, geese hatched in captivity will imprint on humans, dogs, or other animals they first encounter. Researchers who raise goslings from the time they hatch often find themselves courted by the males when they become adults—an unfortunate side effect of imprinting.

Knowledge of the imprinting process has come in handy by allowing conservation organizations to teach migratory patterns to endangered birds. Whooping cranes were reintroduced to Wisconsin by imprinting captive-reared chicks on an ultralight aircraft made to look and sound like an adult crane. The whooping cranes flew behind the aircraft to establish a pathway between their wintering grounds in Florida and their breeding grounds in Wisconsin, thus reestablishing an eastern migratory population of whooping cranes.

Imprinting also serves an important reproductive function. In some cases, early imprinting determines preference for future pairing. This specialized form of imprinting, called sexual imprinting, enables birds to learn the characteristics of their siblings, which later influences their mating preferences as adults. Experiments with mallards and black ducks have demonstrated that females preferred males of the type they were raised with, even when ducklings were raised by parents of another species.

Lesser snow geese, which have both blue and white color phases, choose mates based on their experience with siblings and parents. Therefore, a blue-phase gosling raised with blue-phase siblings and parents will later choose a blue-phase partner most of the time. Ultimately, female choice is an interaction of “like-self” learning and the existence of the appropriate male courtship displays for that species.

Luckily, “like-self” pairing does not occur in waterfowl species that exhibit parasitic nesting behavior. One clear case of genetic hard-wiring occurs in waterfowl species that lay their eggs in the nests of other species. In North America, hen redheads often lay eggs in canvasback nests, and subsequently the redhead ducklings are raised by canvasbacks. But being a redhead is hard-wired, because redheads do not pair with canvasbacks later in life.

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