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NMSU researchers seek to solve mysteries surrounding the extinct Carolina parakeet

The Carolina parakeet was once common across the eastern United States, but about 100 years ago it rapidly went extinct, leaving behind many mysteries. Using genetic evidence from specimens held in museums, researchers at New Mexico State University have discovered that this unique North American species is most closely related to a group of tropical parakeets in the genus Aratinga. They also found that some of the other species in that genus belonged in different genetic groups. Their findings have been published in the April edition of the ornithological journal, The Auk.

Timothy Wright sitting at the lab bench with some tools of his scientific trade
Timothy Wright, a biology professor at NMSU, works with genetic samples used in a study of evolutionary relationships among living species of parrots and the extinct Carolina Parakeet. (NMSU photo by Tonya Suther)

A Michael Rothman painting illustrates Carolina parakeets in one of their favored habitats, the bald cypress swamps of the southeastern United States. (Copyright ACE coinage)

A detail of a painting by Michael Rothman reconstructs the flight of the extinct Carolina parakeet (Copyright Michael Rothman)

"These data provide the first accurate picture of who were the Carolina parakeet's closest relatives," said Timothy Wright, associate professor of biology at NMSU. "They also show that that Aratinga is not a 'good' taxonomic name. Experts in taxonomy will want to reclassify these groups, so that each different group carries its own name. Some species currently in Aratinga will keep that name, while others will be renamed."

Wright studies the genetic relationship of parrots, work that has taken him into the fields of Costa Rica and Mexico. At NMSU, his research involves building a family tree of parrots for a better understanding of their abilities to learn vocalization.

Researchers were publishing the familial data when Jeremy Kirchman, the curator of birds at the New York State Museum, contacted Wright with questions about where the Carolina parakeet fit in.

"Some big mysteries remain about this Carolina parakeet," Wright said. "We don't know why it went extinct, and we don't know how it got to North America in the first place. What are the adaptations that really allowed it to live in an area and climate where no other parrot lives?"

Historically, the Carolina parakeet, with its bright yellow head and green body, was the only parrot ever found in North America. The last captive one died in 1918 at the Cincinnati Zoo, and the last reports of wild population came up until the 1930s, where they could be seen in South Carolina and the Florida swamplands.

Since the bird's demise came before ornithology, scientists have limited knowledge about the bird's diet and nesting habits. They only know that the parakeet looked similar to parrots from the genus Aratinga, which have narrow bills and slender bodies with long wings and tails. Wright said its putative relatives could be found in the Caribbean Islands and into Central and South America.

To solve the mysteries, researchers set out to find its closest relative. For that, they used DNA, the standard tool for explaining evolutionary relationships.

"Typically, DNA is easy to get from a blood sample or even a feather sample or a tissue sample, from living birds or recently living birds, but it's much trickier to get it from birds that have been dead for a while," Wright said. "There is DNA in museum specimens, but it's fairly degraded and it's hard to get out."

Wright and Erin Schirtzinger, a former doctoral student in his lab, collaborated with Kirchman, who is an expert at ancient DNA extraction and amplification, and compared the DNA of museum specimens with modern-day parrots.

To avoid contamination of the samples, Kirchman extracted DNA from four different Carolina parakeet museum specimens in New York, while Wright and Schirtzinger, sequenced modern-day parrots at NMSU. Kirchman came up with two samples for comparison that resulted in answers for researchers.

"So, the answers made some sense," Wright said. "We found that the closest relatives were birds that did look like the Carolina parakeet, with bright yellow and orange plumage. We also found that some of the other species that had been classified in this genus Aratinga were in very different genetic groups, suggesting that the whole genus Aratinga needs to be reclassified."

With the genetic mystery solved, questions still remained about how and when the bird arrived in the United States. Wright's current hypothesis is that its ancestors flew from South America and over the Isthmus of Panama as it was forming some three million years ago.

"The timing is about right," he said. "It's possible that those parrots were flying over while the volcanoes were coming up and the land bridge was being formed."

The findings have provided additional insight into the behavior of the parakeet as well as what it might have sounded like according to Wright.

"When I look at the vocalizations of all of the species of parrots that are still living that are found in that group, they're very similar to each other, that suggests we can actually recreate the sound of the Carolina parakeet or our best guess of what it sound like as it was flying around North America 100 years ago before it went extinct," Wright said.

He also hypothesized about why the bird went extinct. Known to be a crop pest, one of the possible reasons is that farmers had killed them.

"When some members of the flock were shot and fell to the ground, they may have been only wounded and calling out," Wright said. "The flock mates would continue circling around and come right back to the area, and be shot at again rather than flying away."

Other possibilities include disease and predators as well as too few nesting sites. Wright said a further understanding of why the parakeet went extinct would help prevent extinctions in the future.

"We're still left with what I find as an interesting puzzle that is worthy of more examination, and as a scientist, that pleases me," Wright said. "I always like to think about what the next question is that I can ask."

For more information, visit The Wright Lab at http://biology-web.nmsu.edu/twright/index.html.