Ostriches And Emus Once Flew? Study Reveals Their Ancestors Crossed Oceans By Air

Last Updated:September 17, 2025, 19:00 IST

The big mystery scientists have faced for years is how these birds, all of which cannot fly today, ended up on continents separated by oceans

Earlier theories suggested their ancestors were spread across the world when the ancient supercontinent Gondwana broke apart 160 million years ago. (AI-generated image)

A new study has found that the ancestors of modern-day flightless birds like ostriches, emus, and kiwis were once capable of flying, and may have crossed oceans by air to spread across different continents.

The research, published in the journal Biology Letters by the Royal Society, was led by Klara Widrig from the Smithsonian Museum of Natural History in the United States.

The team studied a fossil from a bird known as Lithornis promiscuus, believed to be one of the oldest ancestors in the palaeognath family—a group that includes ostriches in Africa, emus and cassowaries in Australia, rheas in South America, and kiwis in New Zealand.

The big mystery scientists have faced for years is how these birds, all of which cannot fly today, ended up on continents separated by oceans. Earlier theories suggested their ancestors were spread across the world when the ancient supercontinent Gondwana broke apart 160 million years ago. However, newer genetic studies revealed that these bird species split from each other long after the continents had already separated.

To solve this puzzle, Widrig and her team analysed the Lithornis promiscuus fossil, which was found in Wyoming, US, but had been stored in the Smithsonian’s collection. Unlike many bird fossils, this one was well-preserved and had not been crushed, allowing scientists to scan and study the breastbone—where flight muscles attach.

Their analysis confirmed that this ancient bird was indeed capable of flight, likely either by steady wing-flapping or by gliding.

But why did they stop flying?

According to the study, the shift towards flightlessness likely began after the extinction of the dinosaurs around 65 million years ago.

With no major predators left on land, birds no longer needed to fly to escape danger and could get all their food from the ground. Over time, evolving flightlessness saved energy and allowed some species to become fast runners, like ostriches and emus, or even intimidating creatures like the cassowary.

“With all the major predators gone, ground-feeding birds would have been free to become flightless, which would have saved them a lot of energy," Widrig said.

The researcher also pointed out that these findings offer key insight into how and why today’s large, flightless birds evolved as they did.

(With inputs from AFP)

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