In centuries past, large flocks of noisy, brightly colored parrots squawked their way across the United States—from New England, to Florida, to eastern Colorado. The Carolina parakeet, or Conuropsis carolinensis, was the only parrot native to the eastern part of the country. But by the beginning of the 20th century, it had disappeared.
Experts believe that humans played a prominent role in the species’ extinction. The clearing of forests to make way for agricultural land destroyed the birds’ habitat and may have contributed to their loss. They were hunted for their vibrant feathers of green, yellow and red, which made a popular addition to ladies’ hats. Farmers considered them pests and killed them in large numbers; the parrots were easy targets, due to their unfortunate tendency to congregate around wounded flockmates.
But as Liz Langley reports for National Geographic, some experts have speculated that causes not directly driven by humans—like diseases spread by poultry and natural disasters that fragmented the Carolina parakeet’s habitat—may have contributed to the species’ decline. Hoping to shed new light on the issue, a team of researchers sequenced the Carolina parakeet’s genome—and found that human causes were likely the sole driver of the bird’s abrupt extinction.
To conduct their analysis, the team looked at the tibia bone and toe pads of a preserved parakeet specimen held in a private collection in Spain. Because its DNA was fragmented, the researchers also sequenced the genome of the Carolina parakeet’s closest living relative, the sun parakeet, which gave them a more complete picture of the extinct bird’s genetic profile.
The researchers were specifically looking for signs of a drawn-out decline that might have started before humans began hunting the birds extensively—signs like inbreeding. They found that after the Last Glacial Period around 110,000 years ago, Carolina parakeets began experiencing a population decline that continued until recent times—but the still-extant sun parakeet’s decline was stronger, according to the study.
Crucially, the researchers didn’t discover evidence of inbreeding that you might expect to see in a species that has been endangered for some time, which suggests the parakeet “suffered a very quick extinction process that left no traces in the genomes of the last specimens,” the researchers write in Current Biology. And when extinction happens at a rapid pace, “human action is common,” study co-author Carles Lalueza tells Ryan F. Mandelbaum of Gizmodo.
What’s more, the study authors did not find a significant presence of bird viruses in the Carolina parakeet’s DNA, though they acknowledge that further research is needed to rule out poultry disease as a driver of the bird’s extinction. For now, however, they conclude that the parakeet’s extinction was an “abrupt process and thus likely solely attributable to human causes.”
Earlier this month, a separate team of researchers came to the same conclusion about the disappearance of the great auk, a large, flightless bird that appears to have been wiped out by rapacious hunters. These cases offer sobering insight into how quickly humans are capable of decimating a species; the Carolina parakeet, Lalueza tells Mandelbaum, likely went extinct within “the order of [a] few decades.”