Human Colonization Triggered Massive Prehistoric Bird Extinction: Study

By Staff Reporter on April 3, 2013 3:23 AM EDT

Birds
Zebra finches (representational image) (Photo: Reed Hutchinson/UCLA)

A new study has revealed that about 1,000 prehistoric birds became extinct after human colonization in the Pacific Islands.

A team of international researchers studied the extinction rates of non-perching land birds in the Pacific Islands from 700 to 3,500 years ago. They found that human colonization of the Pacific Islands most likely caused the extinction of ancient birds.

Scientists have already known that extinction rates of birds were high in the Pacific Islands, but they were not sure as to how many of them died as the fossil records were incomplete. Previous estimates of bird extinction varied from 800 to 2,000 species.

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For their new study, the research team analyzed 41 Pacific islands such as Hawaii and Fiji and collected fossil records of extinct birds. Using a mathematical model, they determined the extinction rates of birds on each of the Pacific Islands.

They found that nearly 983, or two-thirds, of land bird populations became extinct between the years of the first human arrival and European colonization. The disappearance of these birds has been linked to deforestation, overhunting and introduction of new species.

"We calculate that human colonization of remote Pacific islands caused the global extinction of close to a thousand species of nonperching land birds alone," Alison Boyer, a research assistant professor from University of Tennessee at Knoxville, said in a statement. "However, it is likely there are more species that were affected by human presence. Sea bird and perching bird extinctions will add to this total."

Boyer and his colleagues also found that the extinction rates of birds differed depending on the island as well as species traits. Larger islands had lower extinction rates as the population of birds was larger in such islands. Islands experiencing more rainfall too had lower extinction rates because there was less deforestation by settlers.

Flightless, large-bodied birds had higher rate of extinction as they were easier to hunt. Moreover, their lower growth rate made it harder for them to recover from overhunting or habitat loss.

The findings of the study are published in the journal of the Proceedings of the National Academy of Sciences.

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