The kiwi does not fly despite its wings because it is a bird incapable of flying. The kiwi's wings have evolved to become small vestigial structures, mainly used to maintain balance during its terrestrial movements.
The kiwi has a stocky, compact body, with tiny wings that are practically invisible beneath its thick plumage. These atrophied wings are too small to provide the lift necessary for flight. Its sternum, unlike that of most birds, lacks a developed bony crest (the keel), which normally serves as an anchor for powerful flight muscles. As a result, these muscles are greatly reduced in the kiwi. In contrast, it has thick, muscular, and robust legs that are perfect for running, digging, and effectively walking on the ground. Its morphology is clearly that of a specialized ground bird, far removed from what is needed to soar through the air.
The kiwi has developed particular adaptations to live close to the ground. For example, its greatly reduced wings release energy that allows it to strengthen other useful functions: like its powerful legs with sturdy claws, perfectly suited for walking and digging. Its highly developed sense of smell partially replaces its vision, which is rather poor, allowing it to detect its prey beneath the plant litter or soil. Even its feathers, resembling thick down, are more effective for blending into the forest environment rather than for flying. This terrestrial lifestyle has pushed it to become discreet, robust, and well-equipped to stay quietly on the ground throughout its life.
New Zealand, an isolated island for millions of years, was devoid of large land predators: no carnivorous mammals, no snakes. As a result, the kiwi did not need to fly to stay safe. It could comfortably stay on the ground, digging in the soil for its food. The result: its wings gradually reduced and became useless, as saving energy by avoiding the maintenance of muscles and bones intended for flight was all beneficial. Unfortunately, when predators like rats, cats, or dogs eventually arrived on the island, this peaceful evolution made the kiwi particularly vulnerable.
Like the kiwi, the ostrich, the emu, and the cassowary, they have very small wings that are useless for flying. Their massive bodies and sturdy legs are sufficient for moving quickly on the ground. In the case of the ostrich, its long, muscular legs more than compensate for its inability to fly. The same idea applies to the emu and the cassowary: tiny wings, but remarkable power in their legs for running or defending themselves. The penguin, also equipped with wings that cannot fly, has opted for an aquatic specialization: its wings act as true flippers. The kiwi, on the other hand, does not run fast and is not an exceptional swimmer, but its reduced wings also clearly illustrate how evolution sometimes eliminates a capability that has become unnecessary. All these birds demonstrate the same principle: when a species no longer uses a capability (in this case, flight), it eventually discards it to adapt to its way of life.
The kiwi is a national symbol of New Zealand, so much so that the country's residents often refer to themselves as 'Kiwis,' in reference to this emblematic bird.
The kiwi has feathers similar to fur. Unlike the feathers of flying birds, they do not have the rigid structures necessary to support flight.
The kiwi's egg is one of the largest relative to its body size among all birds. A single egg can represent up to 20% of the female's weight, making laying quite taxing.
The kiwi's tiny and hidden wings are often invisible beneath its thick feathers, so much so that many are unaware that this bird has wings, even though they are non-functional.
The kiwi indeed shares a common ancestor with flying birds. However, due to geographical isolation, the absence of natural predators, and abundant ground food resources, its species gradually lost the ability to fly, rendering its wings unused.
No, the kiwi is not the only one. Other notable examples include the ostrich, the emu, the cassowary, and the rhea. All of these birds have evolved to have a sturdy body adapted to life on the ground and have lost the ability to fly due to similarly reduced wings.
Although they do not reach the speed of ostriches, kiwis have strong legs that allow them to run effectively over short distances. This serves as their main defense against potential predators.
Yes, the kiwi does indeed have wings, but they are extremely small and atrophied, hidden under its dense and fluffy plumage. They do not allow it to take off or fly at all.
In kiwis, the wings no longer have a function related to flight. They have become almost vestigial over the course of evolution. Today, they may play a minor role in body balance or simply remain unused as they do not provide any particular advantage.
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