Flightless birds would be four times as diverse if not for humans

If not for human-driven extinctions, there would be at least four times as many flightless bird species today, according to a new study from University College London. The experts found that flightlessness evolved in birds much more often than what would be expected by looking at only living birds.

According to the researchers, the study shows how human-driven extinctions have biased our understanding of evolution.

“Human impacts have substantially altered most ecosystems worldwide, and caused the extinction of hundreds of animal species,” said study lead author Dr. Ferran Sayol.

“This can distort evolutionary patterns, especially if the characteristics being studied, such as flightlessness in birds, make species more vulnerable to extinction. We get a biased picture of how evolution really happens.”

The experts compiled a comprehensive list of all the bird species that are known to have gone extinct since humans emerged. They identified 581 bird species that were wiped out from the Late Pleistocene 126,000 years ago to the present day. The researchers believe that nearly all of the extinctions were caused by human influences.

The analysis revealed that 166 of the extinct bird species were flightless. Today, there are only 60 bird species that lack the ability to fly. 

The study also showed that flightless birds were much more diverse than what was previously assumed. Furthermore, the findings confirm that flightless species were much more likely to go extinct than species that could fly.

“Many bird species can become flightless in environments without their usual predators, for example on islands. Flying expends a lot of energy that birds can use for other purposes if they don’t need to take to the air. Unfortunately, though, this makes them easier prey if humans – and their associated rats and cats – suddenly turn up,” said study co-author Professor Tim Blackburn.

“Extinction has all too often been the result, and is likely to continue as flightless birds are overrepresented, compared to avian species, on global lists of animals under threat.”

The researchers discovered that most island groups worldwide had flightless birds before humans arrived, and some of these regions were hotspots. New Zealand once had 26 flightless bird species such as the extinct moa, while Hawaii had 23 species – all of which are now extinct.

“Our study shows that the evolution of flightlessness in birds is a widespread phenomenon,” said Dr. Sayol. “Today, most flightless species are penguins, rails or ostriches and their relatives. Now, only 12 bird families have flightless species, but before humans caused extinctions, the number was at least 40. Without those extinctions we would be sharing the planet with flightless owls, woodpeckers and ibises, but all of these have now sadly disappeared.”

The study is published in the journal Science Advances.

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By Chrissy Sexton, Earth.com Staff Writer