Humans are to blame for the extinction of many hundreds of bird species over the last 20,000 to 50,000 years, according to a new study from Tel Aviv University.
In collaboration with researchers at the Weizmann Institute, the team has investigated a major extinction event that ultimately led to the disappearance of about 10 to 20 percent of all avian species.
The experts report that the vast majority of the extinct bird species shared several features: they were large, lived on islands, and many of them were flightless.
Study lead author Shai Meiri is a professor in the School of Zoology at the George S. Wise Faculty of Life Sciences and the Steinhardt Museum of Natural History at Tel Aviv University.
“We conducted a comprehensive review of scientific literature, and for the first time collected quantitative data on the numbers and traits of extinct species of birds worldwide. Those that became extinct in the last 300 years or so are relatively well known, while earlier species are known to science from remains found in archaeological and paleontological sites worldwide,” explained Professor Meiri.
“Altogether we were able to list 469 avian species that became extinct over the last 50,000 years, but we believe that the real number is much higher.”
The researchers believe the widespread extinction of birds was primarily driven by humans, who hunted the birds for food. Humans also introduced new animals to islands – such as pigs, rats, monkeys, and cats – that preyed on the birds and their eggs.
The experts’ theory is based on two main facts – the majority of the bird remains were found on human sites, and most of the extinctions occurred a short time after the arrival of humans.
Furthermore, the extinctions were not random, as most of the victims had three major features in common. Approximately 90 percent of the extinct birds lived on islands where they were hunted.
In addition, most of the lost bird species were large, making them an ideal target for hunters. According to the researchers, the body mass of extinct birds was up to 10 times larger than that of surviving birds.
Furthermore, a large portion of the extinct bird species were flightless, which means they would have struggled to evade hunters. The experts found that the number of flightless bird species that became extinct is double the number of flightless species still existing today.
Overall, 68 percent of all known flightless bird species became extinct. The moa bird in New Zealand is one of the best known examples. Within 300 years, 11 moa species fell victim to hunting by humans.
“Our study indicates that before the major extinction event of the past millennia, many more large, even giant, as well as flightless avian lived on our globe, and the diversity of birds living on islands was much greater than today,” said Professor Meiri.
“We hope that our findings can serve as warning signals regarding bird species currently threatened with extinction, and it is therefore important to check whether they have similar features. It must be noted, however, that conditions have changed considerably, and today the main cause for extinction of species by humans is not hunting but rather the destruction of natural habitats.”
The study is published in the Journal of Biogeography.