Visit any of the world’s cites and you will almost certainly encounter hordes of the world’s most ubiquitous and well-adapted avian urban dwellers.
The humble rock dove, or pigeon, is derided as a flying rat, spreader of disease and graceless depositor of mounds of guano. But it is also a prized domestic species that has been bred for nearly 5,000 years as a food source, message deliverer, racer, and show bird boasting a startling array of plumages and physiques.
It is this very popularity that has seen the species transported around the world, where captive and racing birds have escaped into the wild to establish vast feral populations amid the same irritated humans who were responsible for its spread.
Cities suit rock doves superbly. Before they were domesticated, the birds nested along cliffs in Europe, North Africa and parts of Asia. Today, buildings in cities provide plentiful cliff-like environments for their nests; humanity’s wont to waste grants them plenty of grain and other food; and the hostile nature of cities for most large animals protects them from predation, although raptors are increasingly moving into cities to feast on their meat.
Feral rock dove populations are virtually immune to human-led efforts to snuff them out. And new research suggests that pigeon racers could be constantly fueling the wild populations with physical prowess-imbuing genes, helping to spawn today’s urban super-pigeons.
University of Utah researchers studied the genes of hundreds of domestic and free-living pigeons in the United States in an effort to map their family tree. What they discovered, and reported in February in the journal Current Biology, was a free flow of genes from specially bred racing pigeons into the wild.
Anywhere from five to 20 percent of racing pigeons fail to complete any given race. Some fall prey to predators. But others may simply get lost, or choose to not return home, and then blend into wild populations, where they coo and carry on and breed with feral lovers.
“[Racing homers] are bred for speed, endurance and navigation ability,” researcher Mike Shapiro told me. “They’re great flyers, unlike many of the ornamented or other exhibition breeds, so it’s not too surprising that they do well in the wild.”
All free-living rock pigeons in North America are feral, having first arrived some 400 years ago, with modern racing pigeons appearing a couple of centuries ago, Shapiro said, meaning that all of the continent’s populations must have been established by domestic breeds at some point.
“We hypothesized that they probably had major genetic contributions from racing homers because the breed is so popular and they, perhaps more than any other breed, have ample opportunities to fly free and escape,” Shapiro said. “This hypothesis is supported by our genetic data.”
Next time you see a broken-legged pigeon plunging its filthy face into trash strewn by the side of a busy street, spare a moment to give thanks to pigeon racers for potentially growing the species’ vigor. After all, these dumpster divers help push our wasted French fries and other food scraps up a nascent food chain and into the stomachs of the awe-inspiring hawks and Peregrine falcons that also inhabit our cities. That seems better than leaving the food to rot – and belch out its hydrocarbons as climate-changing methane.