A couple days ago CBS Evening News aired the story of a little girl who plays mom to a pet duck. The duck lives in her house (wearing a custom-made duck diaper), sleeps in her bed, and follows her wherever she goes–whether it’s to the pond at the park or trick-or-treating or a sleepover party. It’s the story of a beautiful friendship, and a heartwarming illustration of an avian instinct called filial imprinting. (Watch the video at the bottom!)
To be precise, we’re not talking about all birds–just precocial, nidifugous (“nest-fleeing”) birds. These are fancy terms for birds that were born ready: fully feathered, able to bust out of the nest at the first opportunity. The most common examples are waterfowl–ducks, geese and the like. Contrast this with our stock mental image of bare-fleshed, open-beaked nestlings waiting helplessly for mama bird to deposit regurgitated worms into their mouths. Nidifugous birds would call them candy-asses.
So precocial, nidifugous birds have this natural drive to venture out. But if they didn’t have a mechanism that impelled them to follow a leader, they might waddle off in all directions, including into the hungry jaws of their predators–turtles, raccoons, foxes, big fish, and the list goes on. In these species’ distant evolutionary past, such mavericks and heedless wanderers were weeded out; they bumbled into danger and didn’t live to reproduce. Those that played it safe by velcro-ing themselves to mom were more likely to survive to adulthood, and produce offspring that shared their mother-following tendencies.
Over time, filial imprinting–the instinct to attach to their mother and follow her everywhere–became deeply ingrained in nidifugous birds. This survival imperative is so strong that, if their biological mother is absent at the time imprinting would naturally occur, chicks will imprint on the first moving object they see. Konrad Lorenz, one of the most influential animal behavior scholars in history, identified this phenomenon and then manipulated it to amusing (and enlightening) effect. He found he could get chicks to imprint on him, his boots, other animals, and even a box traveling atop a model train. In each case the birds toddled after these surrogate “imprintees” as devotedly as they’d’ve trailed their own mother.
Manipulating the process of filial imprinting hasn’t just been done for scientific discovery, or laughs. It’s also been an effective tool in wildlife conservation. When the U.S. Fish and Wildlife Service was attempting to establish a second migrating population of endangered whooping cranes, they induced chicks to imprint on an ultralight plane, and then had them fly behind the plane to their designated wintering grounds. Having learned the route this way, the cranes returned to their breeding grounds unassisted. If you’ve seen the movie “Fly Away Home”, based on a true story, this approach will sound delightfully familiar.
A whimsical look at imprinting can be found within the pages of a favorite childhood classic, Are You My Mother? A baby bird hatches while his mom is off searching for food. Finding himself alone, he naively strikes out on quest to find her. But he doesn’t know what she looks like; he hasn’t imprinted on her yet. To him, it’s equally plausible that a cow, an airplane, and a snorting piece of heavy construction equipment might answer affirmatively to his pleading question, “Are you my mother?” It’s probably a good thing all those non-mother entities were sitting still; if they’d sprung into motion, he’d probably have followed. Then the baby bird might’ve ended up imprinting on, say, the cat. And the story would’ve had a far different ending indeed.