Every park has at least one weird duck. It’s the wrong colors—all white, or patchy white; its bill bright storybook orange or its face weirdly red and lumpy. Next to the other ducks it looks oversized and bulky, like a linebacker in a crowd of quarterbacks.
How new species form, and what determines whether they last, is one of the major topics in evolutionary biology; and much of this topic is embodied by that one weird duck.
Nothing better demonstrates the axiom “familiarity breeds contempt” than the pigeon. Pigeons have remarkable navigation skills and are extremely powerful fliers. They perform courtship dances and mate for life (as much as any bird does, anyway). Both parents care for the chicks. They have an adaptation—”crop milk,” a substance that they produce and feed to their chicks, similar in concept (if not physiology) to how we mammals produce milk for our babies—that allows them to breed in habitats most birds could never hope to raise a family in. They thrive in urban environments, making them probably the first and most-often seen wild animal of many city-dwellers. They recognize each other as individuals. They are smarter than you think.
Concerning their usefulness to humans, pigeons are easily raised in captivity and edible. They have been bred into many domestic varieties with strange attributes, such as the propensity to roll over in mid-air. Charles Darwin studied domestic pigeons extensively, and they contributed to the formation of his theory of evolution by natural selection. They have been important message carriers in wartime; pigeons have received the Dickin Medal—like the Medal of Honor, but for animals—32 times, more than any other species (dogs are closing in with 31 medals).
And they come in sparkly colors with crazy eyes.
“Rats with wings,” people say—patently untrue: you can’t get plague from pigeons. “Dirty,” people call them; as if it isn’t our dirt they are wearing, and yet thriving anyhow.
More than fifty years ago, Russian scientists began an experiment in domestication. At that time, silver foxes had been raised for fur for about 100 years already, so their care and breeding was well known. The scientists began their project like this: they would approach the cage of a silver fox and note its response. The fox would crouch, ears flattened, snarling in fear, or else back away as far as it could until its body was vertical against the back wall of the cage. All of the foxes were frightened of the humans—but some less than others. The scientists chose the foxes that showed the least fear of humans, and bred them. Then they did the same with the pups, raising up and breeding the least-frightened of them; and so on and so on.
Young wild silver fox. Photo by Matt Knoth*
The original foxes were as close to wild animals as anything can be after being bred for fur for a century. Their descendants, after many generations of selection for just one thing—tameness, a liking of humans—look and act like dogs. They seek out humans, they whine and lick your face, they wag their tails. They even look like dogs—mostly, like border collies.
Fox kit showing the white markings characteristic of domestication. Photo by Luz Rovira*
Tough Little Birds 