Why Do Flightless Birds Go Extinct So Often?

Flightless birds go extinct so often because most evolved on predator-free islands and never developed a way to escape danger. When humans (and the rats, cats and pigs they brought) arrived, these birds were hunted out or lost their habitats. Of 581 bird species lost in the last 126,000 years, 166 were flightless.

When you think of birds, you probably peg them as masters of flight, but when we rewind to the age when dinosaurs went extinct, the birds that existed back then didn’t soar quite so high. Instead, they kept their heads down, grazing and running free on the land.

Grounded birds were not as rare as they appear to be today. In fact, flightless ibises, geese, owls and rails, along with many more, were a common part of the landscape. They were well and truly alive, but are now sadly gone. One of the last giants to survive was the elephant bird. True to its name, the largest species (Aepyornis maximus) weighed in at roughly 450 to 650 kilograms (1,000 to 1,400 pounds), making it the heaviest bird known to science.

It’s surprising to think that size and strength wasn’t enough to keep these flightless birds alive. From large behemoths like elephant birds to small, odd-looking birds like dodos, they all faced the same unfortunate end.

Although natural events like infamous ice ages and volcanic outbursts cannot be entirely ruled out, it seems like more than a coincidence that these species disappeared shortly after humans encroached on their homes. It’s very likely that our ancestors exterminated them, either to fill their bellies, clothe their bodies or decorate their homes.

Could The Skies Be A Safety Net?

In the case of birds, it definitely can. Research suggests that flightless birds, having lost their ability to fly, have been and remain far more prone to going extinct than volant (flying) birds. (A quick note on terminology: "ratite" refers only to a specific lineage of flightless birds such as ostriches, emus, rheas, kiwis and the extinct moa and elephant bird. Penguins, rails, the dodo and the great auk are flightless too, but they are not ratites, because flightlessness evolved separately in each of these groups.)

Humans are likely to blame for the long list of 581 bird species that have vanished over the past 126,000 years. Of these, 166 possessed wings that were too weak to fly. Flightlessness was once widespread, so if those birds hadn’t been decimated by humans, we’d still share this world with more than 150 independently evolved flightless bird groups. Unfortunately, as it stands, only about 60 flightless species remain, including ostriches, rheas, kiwis, emus and penguins.

Not-so-safe Islanders

The same study found that the rate of extinction for volant birds was comparatively much lower than that of their flightless cousins. The danger was sharpest on islands: roughly 80% of all the bird species lost in this period were island dwellers, and flightless island birds were among the first to disappear. Living on an island, far from any natural predator, turned out to be exactly the wrong place to be once humans showed up.

Many islands worldwide had a good number of flightless birds. Ecologically speaking, they occupied a place in the ecosystem that would normally be filled by mammals. However, this dynamic changed when human settlements appeared. These flightless and naïve birds, who knew nothing about fearing mammals, stood no chance against humans and their non-native pets.

Some island hotspots where flightless birds were prevalent include New Zealand, with 26 species, and Hawaii, with 23 species, all of which are now extinct.

Lacking a crucial defense strategy, such as flight, these grounded birds died out due to easy and opportunistic predation. Human hunters, along with rats, cats, dogs and pigs, led to a severe decline in their population. Some birds that were able to evolve into better runners used that skill to flee from predators and managed to survive.

How Did Different Flightless Birds Go Extinct?

Dodos

These stocky little birds have long been reputed as quite dumb, but that reputation is unfair. Studies of dodo skulls show that its brain was roughly the same size, relative to its body, as that of a modern pigeon, so it was probably no less clever than its surviving relatives. What looked like stupidity was actually fearlessness: having evolved on a predator-free island, the dodo had no instinct to flee, so hunting them was a piece of cake. Now extinct, dodos once thrived in the forests of Mauritius. But when Portuguese and then Dutch sailors arrived on this island in the 1500s and 1600s, it was a death knell for these birds. The pigs and rats that the humans brought ate the dodo’s eggs, making reproduction almost impossible.

Ecosystems quickly declined due to deforestation and habitat loss. Thus, the dodo went extinct within a century of being discovered, wiped from the face of the earth by around 1681.

Moas

The moas were among the last of the giant species to vanish. A group of people known as the Māori were the first settlers of New Zealand. Within roughly a century of their arrival around 1300, the Māori hunted all nine known moa species to extinction. They used the eggshells as water carriers, while the bird’s meat and eggs would feed the village. Additionally, spears, hooks and ornaments were made from the moa’s bones. When a species is hunted during all of its life stages, it has almost no chance of survival.

The elephant bird held on even longer. Aepyornis hildebrandti lasted in Madagascar until roughly 1,500 years ago, making it the longest-surviving of these giant flightless birds. It finally fell victim to deforestation and hunting, despite laying eggs so enormous that a single elephant bird egg held about as much as 160 chicken eggs.

Great Auk (Pinguinus impennis)

This flightless seabird’s defenselessness led to it going extinct in 1844. Having nested on rocky islands along the North Atlantic coasts for thousands of years, the birds were captured in large numbers and slaughtered for food, bait and feathers, especially during the early 1800s. The last known pair was killed on the Icelandic island of Eldey in June 1844.

On a side note, about 80 great auk skins, along with a similar number of eggs, line the shelves of museums today.

Will Present-day Flightless Birds Face The Same Fate As Their Ancestors?

Time seems to be catching up to flightless birds, namely penguins, rheas, ostriches and cassowaries. In addition to those that have already gone extinct, around half of the flightless species still alive today have been listed as threatened or vulnerable. Some of the warning signs are recent: in April 2026, the IUCN moved the emperor penguin up to Endangered as Antarctic sea ice retreats, while the African penguin was uplisted to Critically Endangered in 2024 after its population collapsed. New Zealand’s flightless kākāpō parrot remains Critically Endangered, with only around 250 birds left despite decades of intensive conservation. Humans could seek redemption by investing in measures to save these dwindling populations, but that requires a will we too often lack.

A Final Word

It’s ironic that the evolution of flightlessness, which developed in response to an environment without predators, became the very reason these birds were so easily targeted.

Flightless birds, in particular, are more vulnerable to extinction, as they lack an essential defense to escape predators. Especially for those thriving endemically on remote islands, extinction seemed like a distant threat. Little did they know that foreigners like humans, rats and pigs would rapidly lead to their absolute destruction.