Flightless Birds: 15 Species That Cannot Fly and Why

Why do some birds lose the ability to fly?

Flying is expensive. A flying bird needs huge breast muscles, a deep keel on its breastbone to anchor them, and a light body. All of that costs energy to build and run. When a bird can find enough food on the ground and has no reason to escape into the air, natural selection can favor bigger legs and smaller wings instead.

That is why so many flightless birds evolved on remote islands such as New Zealand, Mauritius and the Galápagos, where there were no native cats, rats or other ground predators. Rails, a family of marsh birds, are especially quick to lose flight after reaching islands. Other birds gave up flying for different reasons: ostriches and emus became too heavy and rely on running, while penguins traded aerial flight for diving.

Flightlessness has evolved many separate times. DNA studies published in 2014 showed that the closest relatives of New Zealand’s kiwis were the extinct elephant birds of Madagascar, not the moas that lived alongside them. This suggests that the ancestors of the big ratites (the ostrich, emu, rheas, cassowaries and kiwis) could still fly when they spread around the world and lost flight independently later.

Flightless birds at a glance

1. Common ostrich

The common ostrich (Struthio camelus) of Africa is the largest and heaviest living bird. Males stand 2.1–2.75 m (6 ft 11 in–9 ft) tall, and their thick, two-toed legs carry them at about 70 km/h (43 mph) in short sprints, the fastest speed of any two-legged animal. Its wings are useless for flight but help it balance and turn while running, and males flash them in courtship. Learn more in our ostrich profile and in Can ostriches fly?.

2. Somali ostrich

The Somali ostrich (Struthio molybdophanes) of the Horn of Africa was recognized as a separate species in 2014. It is about the same size as the common ostrich, but the bare skin on its neck and thighs is blue-gray rather than pink, turning bright blue in breeding males. It is listed as Vulnerable, mainly because of hunting and egg collecting.

3. Emu

The emu (Dromaius novaehollandiae) is Australia’s tallest native bird and the third tallest bird on Earth after the two ostriches, reaching 1.5–1.9 m (4 ft 11 in–6 ft 3 in). Emus are strong long-distance walkers and can sprint at about 48 km/h (30 mph). Their wings are tiny, only about 20 cm (8 in) long, and hidden under shaggy, hair-like feathers. The male alone incubates the eggs for around eight weeks, barely eating or drinking.

4. Southern cassowary

The southern cassowary (Casuarius casuarius) of New Guinea and northeastern Australia is one of the heaviest living birds, outweighed only by the ostriches. Females, which are larger than males, weigh roughly 47–76 kg (103–168 lb). A bony casque tops its head, and the inner toe carries a dagger-like claw up to 12 cm (4.7 in) long. It eats mostly fallen fruit and spreads the seeds of many rainforest trees.

5. Greater rhea

The greater rhea (Rhea americana) of the grasslands of eastern South America is the largest native bird in the Americas, weighing 20–27 kg (44–60 lb). Like the emu, the male builds the nest and raises the chicks, often from eggs laid by several females. A small wild population, descended from escaped birds, now lives in northern Germany.

6. Lesser rhea

The lesser rhea (Rhea pennata), also called Darwin’s rhea, lives in Patagonia and the high Andes. It stands about 90–100 cm (35–39 in) tall and weighs 15–29 kg (33–63 lb). It has relatively large wings for a ratite, which help it balance and turn sharply while running at up to about 60 km/h (37 mph).

7. Kiwis

The five kiwi species of New Zealand, including the North Island brown kiwi (Apteryx mantelli), are the smallest ratites, about the size of a chicken. They are nocturnal, sniff out worms with nostrils at the tip of the bill, and have wings so small that they cannot be seen under the feathers. A female’s egg can weigh up to 20% of her body weight. Four kiwi species are listed as Vulnerable and one as Near Threatened.

8. Kakapo

The kakapo (Strigops habroptilus) of New Zealand is the world’s only flightless parrot and also the heaviest, with males weighing 1.5–3 kg (3.3–6.6 lb). This green, owl-faced bird is nocturnal and climbs trees, using its wings to parachute down. Introduced cats, rats and stoats nearly wiped it out. It is Critically Endangered, with only a few hundred birds alive, each one known by name.

9. Takahe

The South Island takahe (Porphyrio hochstetteri) is the largest living rail, a stocky blue-green bird with a heavy red bill. It was thought extinct after 1898 but was rediscovered in 1948 in a remote valley of the Murchison Mountains. Careful management has raised the population to around 500 birds, but the species is still listed as Endangered.

10. Weka

The weka (Gallirallus australis) is a chicken-sized brown rail found only in New Zealand. It is a bold, curious omnivore that eats insects, worms, fruit, lizards and eggs, and it often searches camps and houses for scraps, sometimes carrying off shiny objects. Weka can run fast and swim well but cannot fly. The species is listed as Vulnerable.

11. Emperor penguin

All penguins are flightless, and the emperor penguin (Aptenodytes forsteri) is the largest, weighing 22–45 kg (49–99 lb). Its wings have become stiff, narrow flippers that power it through the water, and one bird was recorded diving to 564 m (1,850 ft). For the full story of how penguins swapped air for water, read Why can’t penguins fly?

12. Galápagos penguin

The Galápagos penguin (Spheniscus mendiculus) is the only penguin that lives on the equator, with some birds found just north of it. Cool, nutrient-rich ocean currents make its tropical home possible. It is one of the rarest penguins and is listed as Endangered, as warm El Niño years cut its food supply.

13. Galápagos cormorant

The flightless cormorant (Nannopterum harrisi), shown in the photo above, lives only on Fernandina and Isabela in the Galápagos. It is the only cormorant in the world that cannot fly. Its wings are about one third of the size needed to lift its 2.5–5 kg (5.5–11 lb) body, and it chases fish and octopuses underwater with powerful kicks of its webbed feet. It is listed as Vulnerable.

14. Falkland steamer duck

Three of the four steamer duck species of southern South America are flightless, including the Falkland steamer duck (Tachyeres brachypterus). These heavy sea ducks get their name from the way they escape: they splash across the water, flapping their wings and paddling their feet like an old paddle steamer. They are also famously aggressive toward other waterbirds.

15. Inaccessible Island rail

The Inaccessible Island rail (Laterallus rogersi) is the smallest flightless bird alive, about 12.5 cm (5 in) long and weighing roughly 35 g (1.2 oz). It lives only on Inaccessible Island in the Tristan da Cunha group, which has never had rats or cats. That lucky isolation is why it survives when many other island rails have vanished, but it is Vulnerable because a single accidental introduction of predators could wipe it out.

Extinct flightless birds: dodo, moas, elephant birds and great auk

Many flightless birds disappeared soon after people reached their homes. The dodo, a giant ground pigeon of Mauritius, was first recorded by Dutch sailors in 1598 and was last reliably seen in 1662, wiped out by hunting, habitat loss and introduced animals.

New Zealand’s nine species of moa were the only birds with no wings at all. The largest stood about 3.6 m (12 ft) tall with the neck stretched up and weighed around 230 kg (510 lb). All were hunted to extinction within about a century of people settling New Zealand around 1300 AD. Madagascar’s elephant birds, which laid the largest known eggs of any land animal, died out around 1000 AD.

In the North Atlantic, the great auk, a flightless seabird about 75 cm (30 in) tall, was hunted for its meat, eggs and down. The last two confirmed birds were killed off Iceland in 1844. Today, the main threats to the survivors are introduced predators, habitat loss and, for penguins, warming seas.