Caribbean Bird Fossils Reveal Human-Caused Mass Extinction Event

About 6,000 years ago, the first people arrived on the Caribbean island of Haiti. Birds were plentiful at the time, inhabiting the trees and forests of the nation. Yet suddenly, these species began to die off, perishing during a mass extinction event that scientists had previously attributed to the arrival of people. Now, though, a study of Haiti bird fossils has indicated that the first human encounter didn't cause the island's birds to die simultaneously. Instead, some species were more resilient than others.

The researchers used comparisons with modern bird bones in order to identify 23 species from the 4,857 bird fossils that were excavated from a cave in southeast Haiti. The most common bird that they found were the Zenaida Dove, the Black Swift, the Least Pauraque, the Hispaniolan woodpecker and a newly discovered extinct woodcock. The researchers estimated that while the woodcock survived the initial arrival of humans 6,000 years ago, it was subsequently killed off after the arrival of Europeans in 1492.

Why so many species in one cave? The researchers believe that the location was probably a roost where owls deposited boney pellets of their prey. In addition to the bird bones, they also found remains from frogs, lizards, snakes, bats and rodents.

By using radiocarbon dating, the researchers were able to determine the site's age and, consequently, the age of the birds' bones. It allowed them to gather a clear picture of what species were still present during a period when humans were having a large impact on the surrounding ecosystem.

The fossils showed much greater diversity than there is today. Of the present-day species found at the site, about one-third are considered threatened, and four of the 23 species are no longer found in the area.

"When you take a look at what could've caused this, it really does just keep pointing to humans," said lead author David Steadman in a press release. "I just think it's habitat loss from people and introduction of non-native, invasive plants and animals. It's the same thing we're dealing with in Florida now--who knows what the pythons are going to wipe out in the Everglades."

Yet while there's no doubt that humans killed off some species, others were able to hang in a bit longer. The radiocarbon dating uncovered a much later time period than the arrival of the first people to the island, which reveals that the mass extinction didn't occur suddenly, as previously thought.

This study isn't only relevant to finding out the history of Haiti, though. It also may help future conservation efforts. It could allow researchers to predict future ecological impacts--such as habitat loss and the introduction of invasive species. This could lead to better preservation of species that still thrive in the area.

The findings are published online in the journal The Holocene.