Dr. Tim Blackburn, University of Birmingham – Human Migration and Bird Extinctions
In today’s Academic Minute, Dr. Tim Blackburn of the University of Birmingham reveals the connection between human migration and the extinction of tropical birds.
Tim Blackburn is an honorary professor of macroecology at the University of Birmingham and Director of the Institute of Zoology in London, England. His recent research has addressed the ecology and evolution of invasions, especially the causes of establishment success, and how invasions by exotic organisms (including humans) relate to extinction of native bird species on oceanic islands.
Dr. Tim Blackburn – Human Migration and Bird Extinction
The remote islands of the eastern Pacific were the last habitable region on Earth to be colonized by humans. Fossils show that there was a major extinction of bird species soon after the first people arrived, but just how many species were actually lost is unknown. This is because the fossil record is imperfect, and a large number of species would have vanished without leaving any trace.
In fact, we can estimate this number by seeing how well fossils preserve bird species that survived the arrival of people. If there are lots of extant species missing from the fossil record, then lots of extinct species will be missing too. We can use the mismatch to estimate how many. Here we run into further complications, however. Features of islands and species that affect the quality of the fossil record are also likely to have affected how many species went extinct, and this may bias our estimates.
Our research used new statistical techniques that allow us to model extinction rates while at the same time accounting for uncertainties in the fossil record, and for variation in extinction rates among species and islands. These models suggest that around two-thirds of Pacific bird species went extinct soon after the first humans arrived, and that two-thirds of these are missing from the fossil record. More species were lost from smaller, drier islands, as these suffered more habitat destruction and have fewer refuges from hunters. Flightless and large-bodied species are the preferred targets of these hunters, and were more likely to have gone extinct.
Our results imply that thirteen hundred bird species were lost from tropical Pacific islands following the arrival of the first humans. To put that in perspective, it equates the loss of around one in every 10 bird species that existed at the time.
Production support for the Academic Minute comes from Newman’s Own, giving all profits to charity and pursuing the common good for over 30 years, and from Mount Holyoke College.