Saving a Species by Splitting It: The Case of the Ruddy-headed Goose

From the Autumn 2016 issue of Living Bird magazine. Subscribe now.

The Ruddy-headed Goose is a beautiful, plump, russet bird that historically nested by the thousands in Tierra del Fuego and southern Patagonia. But the Argentine government declared it and two related species an “agricultural plague” in the 1930s, because the birds spent winters foraging in Buenos Aires crop fields. As many as 250,000 eggs were destroyed each year through the 1970s, and hunters were given open season on the birds until 1998.

Now only about 1,000 Ruddy-headed Geese remain in all of Argentina and Chile. But oddly, it’s still listed as Least Concern by the International Union for the Conservation of Nature—the same designation applied to Red-winged Blackbirds and Downy Woodpeckers.

The reason for this low ranking lies about 270 miles east of Argentina, on the low rocky expanses of the Falkland Islands, where up to 81,000 more Ruddy-headed Geese live. According to the IUCN, the total population size for the Ruddy-headed Goose does not approach the thresholds for Vulnerable status, let alone Endangered.

But those island geese are subtly smaller than the ones on the mainland, and they have lost the instinct to migrate. Perhaps they aren’t the same species at all.

It was this hunch that led a group of evolutionary biologists to embark on a conservation study of sorts. They gathered DNA samples from 46 geese, including Ruddy-headed Geese from the mainland and the Falklands, as well as two other species from the Chloephaga genus (Upland and Ashy-headed). In a four-day sequencing binge back at the Cornell Lab of Ornithology in upstate New York, they compared the three species at more than 1,000 individual points in their DNA. In April, they published their results online in the Journal of Biogeography: Ruddy-headed Geese from the Falklands have been separated from their mainland relatives for as long as 200,000 years. Genetically, they are as different from each other as an entirely distinct species, the Ashy-headed Goose.

Coauthor Leonardo Campagna, an Argentine native and Cornell Lab research associate, is hopeful that the study will improve the prospects of the imperiled mainland form.

“If you draw attention to it, it turns from this random red goose into ‘the Ruddy-headed Goose,’” he says. “And that would allow people to notice the problem” and provide a political impetus to fix it. “That’s my hope,” he says.

Given enough time, islands have a habit of doing mischievous things with evolution. Species find their way to islands and then, in isolation, begin to survive, adapt, and drift into new forms. It’s how a small flock of finches that found their way to Hawaii became some 30 species of honeycreepers, and how an unassuming dove that once landed on Mauritius became the waddling, earthbound Dodo. Even just a little isolation can work its effects. The Falklands (known to Argentinians as the Islas Malvinas) are only a few hundred miles off South America, little more than a hop, skip, and a jump for a goose. The mainland Ruddy-headed Goose migrates nearly twice that distance to its wintering grounds in Buenos Aires province each year.

If the Falklands and continental populations were to be split into separate species, the mainland’s population of about 1,000 individuals would immediately meet IUCN endangered criteria—drawing international recognition to the bird and its plight. That attention could arrive in the nick of time, as one of the main recent threats to the species is also international: illegal hunting by foreign tourists visiting boutique hunting lodges.

Argentina’s reversed seasons and relatively permissive regulations make it attractive to Northern Hemisphere hunters, who can book a weeklong stay at a grand Argentine lodge, and—according to outfitters’ promotional materials—expect to shoot hundreds or even thousands of doves, quail, ducks, and other birds in a matter of days. Argentina banned the hunting of Ruddy-headed Geese in 1998, but Upland and Ashy-headed geese remained legal.

Through 2010, “you could go every day of the year to Argentina, to Buenos Aires, with hunting companies, and they will have no bag limits,” said Mariana Bulgarella, who was a study coauthor as a postdoctoral researcher at the University of Minnesota. “You can collect all the Chloephaga you find. And it’s almost impossible to distinguish Ruddy-headed Goose from female Upland Goose. Basically, [Ruddy-headed Geese] were killed off on their wintering grounds.”

Finally in 2011, the Argentine government banned hunting Upland and Ashy-headed geese as well, but a 2013 report identified illegal hunting as a significant continuing problem.

“Maybe European hunters don’t know it’s forbidden,” said Cecilia Kopuchian of the Center for Applied Ecology of Argentina’s National Research Council, the study’s lead author. “With this study we can make the alert that this is something different from the Malvinas population, so it must be conserved.”

The mainland Ruddy-headed Goose may yet recover. Efforts are underway to curb predation by introduced gray foxes and mink in Tierra del Fuego, and in parts of Argentina signs inform people that the geese are no longer legal to hunt. In Chile, a small captive-breeding program is underway, informed by the study’s finding that there has been essentially no gene flow recently between the Falklands and the mainland.

“If the results of our study had been different and all the genetics were similar, we would have proposed to reinforce the population with Malvinas birds,” Kopuchian said. “But they are not adapted to the Patagonian landscape. They have different evolutionary histories.” As such, the program will only use geese from the mainland population.

The study also found, surprisingly, that the mainland form has about double the genetic diversity of the Falklands form. In essence, the mainland birds are far less inbred than the Falklands birds, despite having far lower numbers. The finding leaves hope that there’s enough genetic diversity to keep the population resilient as it recovers.