Birds are synonymous with flight, soaring high above the ground on outstretched wings. But did you know that some remarkable bird species actually have no legs? If you’ve ever wondered how these unique birds manage to get around, you’re not alone.
We’ll explore everything you want to know about these fascinating feathered creatures in this comprehensive guide.
If you’re short on time, here’s a quick answer to your question: While uncommon, there are a few flightless birds like kiwis and cassowaries that have extremely reduced or completely absent legs. They survive by adapting with different techniques like sliding on their bellies, using their wings for balance, and living in dense habitats near food sources.
Flightless Birds With Vestigial or Absent Legs
Kiwis
Kiwis are unique flightless birds found only in New Zealand. They belong to the genus Apteryx and are closely related to the extinct moa birds. There are five species of kiwis alive today, the largest being the Great Spotted Kiwi (Apteryx haastii) which can grow up to 18 inches tall and weigh up to 7 lbs.
Kiwis have tiny vestigial wings and no tail. Their legs are very short but powerfully built. They use their strong legs and claws to tunnel through soil and leaf litter looking for insects, worms, and other small prey.
Since kiwis rely on smell and touch more than sight to find food, they have highly developed nostrils and whiskers at the end of their long beak which they sweep back and forth across the ground as they probe the earth.
Once widespread across New Zealand, habitat destruction and predation by invasive mammals brought kiwis to the brink of extinction. But thanks to intensive conservation efforts, all five species have been brought back from the edge.
The total kiwi population is now over 68,000 birds and growing, up from an all-time low of fewer than 25,000 in the 1990s (per Kiwis for Kiwi). But they still face an uphill battle for survival and remain endangered.
Cassowaries
Cassowaries are large flightless birds most closely related to emus that inhabit the dense forests of New Guinea, northeastern Australia, and nearby islands. There are three living species of cassowary: the Southern Cassowary (Casuarius casuarius), Northern Cassowary (Casuarius unappendiculatus), and Dwarf Cassowary (Casuarius bennetti).
These birds stand up to 6 feet tall and weigh up to 165 lbs, making them the third heaviest bird behind only ostriches and emus. Cassowaries have black plumage, a blue face and neck, a helmet-like crest or “casque” on top of their head, and sharp claws on their toes that can grow up to 4 inches long.
Their small wings have claws at the ends as well.
Cassowaries are mainly frugivorous, feeding on fruits and berries that fall to the forest floor. But they also eat fungi, snails, insects, small vertebrates, and the occasional dead animal (per BES Group).
These big birds play an important ecological role by dispersing large seeds through the forest in their scat.
All three cassowary species are threatened in the wild by habitat loss and fragmentation. Cassowaries are solitary, territorial birds that require large home ranges. Breaking up their forest habitat squeezes populations and increases conflicts with humans.
Only about 1,500 Southern Cassowaries remain in Australia today.
Kagu
The Kagu (Rhynochetos jubatus) is a rare and unusual bird found only in the mountainous forests of New Caledonia. It is the sole living member of the family Rhynochetidae and has no close living relatives.
Kagus have powdery white plumage on their body, wings, and crest. Their head and neck are pale gray, and they have bright orange legs and a long reddish-orange bill. Kagus are about the size of a chicken, standing 20-25 inches tall and weighing 1.5 to 2.5 lbs.
These birds are completely flightless, though their wings are not as reduced as other flightless island birds. Kagus use their wings for balance and signaling more than flying. They have a very unique way of walking and running, bobbing their heads back and forth as they go.
Kagus fill an ecological niche similar to pheasants, foraging on the forest floor for insects, snails, fruits, seeds, frogs, and small reptiles. They are most active at dawn and dusk. During the day, they typically perch motionless on a tree branch where their cryptic plumage hides them from view.
Kagu numbers have dwindled to only about 700 adults remaining today due to predation by invasive mammals and loss of habitat (per IUCN). But kagus still play an important cultural role for the indigenous Kanak people of New Caledonia, who consider the kagu their national bird and feature it on their flag.
Intensive conservation efforts are underway to protect the remaining kagu population and its forest habitat.
Evolutionary Adaptations
Reduced Need to Move Quickly
Birds without legs, such as penguins, do not need to move quickly on land to catch prey or escape predators. Their wings have adapted for swimming and diving, providing them with excellent mobility in the water to pursue fish, krill and other marine creatures (1).
On land, their stout bodies and short legs limit their walking speed, but this is not problematic since they spend most of their time in the sea. Penguins can torpedo through the water at up to 15-20 mph to hunt, far faster than they could ever waddle on land (2).
Wing Structures for Balance
Wings play an important role in balance for flightless birds. Penguins have short, stiff wings that act as flippers underwater. On land, their wings help them maintain stability when navigating rugged, icy terrain (3).
The structure of their wing bones and shoulder joints allow the wings to act as props and counterbalance the weight of their bodies as they walk or toboggan across land (4). This allows penguins to precisely control their body position and navigate effectively on land despite their ungainly waddling gait.
Special Feather Tracts
Feathers are essential for maintaining body heat and waterproofing in cold environments. Flightless seabirds have evolved special feather structures for these functions. Penguins have short, stiff, overlapping feathers that are highly waterproof and help insulate them in frigid Antarctic waters (5).
They also have a thick layer of down feathers for warmth. Other adaptations include bare skin patches on their face and feet that allow for heat exchange (6). The dense, interlocked feathers on a penguin’s body lock in air and repel water, providing excellent insulation even when diving for long periods in icy seas.
References:
- https://seaworld.org/animals/all-about/penguins/adaptations/
- https://www.penguins-world.com/what-speed-can-penguins-swim/
- https://www.sciencelearn.org.nz/resources/1913-adaptations-for-living-in-water
- https://www.amnh.org/exhibitions/penguins/anatomy
- https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/penguin
- https://www.britannica.com/animal/penguin
Behaviors and Habitats
Sliding on Bellies
Birds without legs like penguins and puffins have evolved to slide on their bellies to move around. Their wings have adapted into flippers allowing them to propel themselves forward as they slide across ice, snow or rocks (Audubon).
This helps them conserve energy as they search for food in frigid environments.
Living Near Food
These unique birds nest close to abundant food sources near the ocean. Puffins create burrows on cliffs and islands with access to schools of small fish, while emperor penguins huddle for warmth on ice near open water with krill and fish (All About Birds).
Living next to reliable food allows flightless birds to reduce the energy spent hunting.
Nesting Close to Ground
To keep eggs and chicks safe, puffins dig burrows and crevices in dirt or grass, while penguins cradle a single egg on their feet, warmly tucked under a belly brood flap. Their ground-level nests protect developing offspring from harsh winds and cold.
Survival rates increase significantly thanks to this ingenious, energy-efficient nesting strategy passed down over generations.
Threats and Conservation
Habitat Loss
Habitat loss is one of the greatest threats facing birds without legs today. As natural areas are cleared for agriculture, logging, and urban development, these unique birds are losing the wetlands and forests they depend on.
According to the International Union for Conservation of Nature (IUCN), over 85% of wetlands have been lost worldwide since the 1800s. This has devastating effects on populations of flightless birds that nest and feed in these habitats.
Wetland drainage, dredging, and filling associated with development directly destroys nesting sites and food sources. Forest-dwelling legless birds suffer when logging decimates old growth stands and fragments their habitat.
With less space to roam and fewer places to nest, survivors are more vulnerable to predators and face increased competition for resources.
Conservation efforts are urgently needed to preserve remaining wilderness areas and restore degraded wetlands. Creating protected reserves with buffer zones around key habitat and working with developers to minimize ecological impacts could help safeguard populations.
Ecotourism initiatives focused on these unique birds also have potential to drive conservation, if responsibly managed. Still,habitat loss remains an existential crisis for many flightless species teetering on the brink.
Predators
Flightless birds face heavy predation pressure, as their inability to fly makes them easy targets. Ground predators like foxes, coyotes, wild cats, and pet cats take a heavy toll on species that nest on the ground.
Aerial predators including eagles, hawks, and gulls swoop down on defenseless chicks and eggs. Even fish, snakes, and crocodiles prey on aquatic species.
Adult birds rely on camouflage, hiding, and distraction displays to survive. But eggs and chicks are vulnerable, especially when habitats degrade and nests are more exposed. Studies on kiwis show predators destroy up to 95% of eggs and chicks annually.
Predators also disproportionately target adults during breeding season when birds are more conspicuous.[1] This can quickly devastate populations.
Controlling invasive predators like rats, cats, and foxes through trapping, baiting, and exclusion fencing has proven effective. Captive breeding and hatching eggs in predator-proof enclosures also improves survival.
Ultimately, restoring habitat connectivity and integrity may help flightless birds coexist with native predators as they evolved to do.
Climate Change
Climate change presents a major threat intensifying the challenges legless birds already face. Rising temperatures directly threaten populations adapted to cool climates like penguins. Emperor penguins decline 97% at colony sites that become warmer and rainier.[2] Increased flooding and erosion of coastal nesting areas also endangers beach-nesting seabirds.
Changing rainfall patterns and increased drought alter wetland hydrology, degrading habitat for aquatic species. More frequent extreme weather like tropical storms and marine heatwaves can directly kill birds or destroy nests.
Altered seasons confuse migration and breeding cycles, reducing reproductive success.
Rising seas may shrink coastal habitat and low-lying breeding grounds. Ocean acidification and warming degrade food supplies like fish and krill. Increased competition from expanding warm-climate species also disrupts delicate ecological balances.
Protecting large connected habitat areas and reducing other stressors may help build resilience. But steep ongoing cuts in greenhouse gas emissions are needed to limit changes. Scientists warn that projections for 3-4°C warming this century would exceed the survival thresholds of most penguins, waterfowl, and other flightless birds.
Conclusion
While legless birds are unusual, their unique adaptations allow them to thrive in the right environments. By sliding around dense forests near plentiful food sources, using their wings for balance, and nesting close to the ground, these tenacious avians continue to inspire awe in nature lovers around the world.
Next time you gaze up at birds overhead, remember the diversity of the avian world – including some remarkable species making their way across the earth without ever taking flight.