Birds are widely recognized for their ability to soar through the skies. However, some birds have lost the ability to fly through evolutionary processes. These flightless birds have developed characteristics that allow them to thrive in terrestrial or aquatic environments.
Meet the Flightless Birds
The ostrich, the largest living bird, is native to African grasslands and savannas. Standing up to 9 feet tall and weighing over 300 pounds, ostriches have long, powerful legs with two toes, allowing them to run at speeds. Australia’s emu, the second largest living bird, can reach heights of 5.7 feet and weigh over 100 pounds. Emus have three toes on each foot and shaggy, grey-brown feathers.
New Zealand’s kiwi is a pear-shaped bird with loose, hair-like feathers, strong legs, and no visible tail. Primarily nocturnal, kiwis possess an exceptional sense of smell, with nostrils located at the tip of their long bills. Another distinctive New Zealand native is the kakapo, the world’s only flightless and nocturnal parrot. This large parrot can weigh up to 9 pounds and has moss-green plumage that provides excellent camouflage in its forest habitat, along with an owl-like facial disc.
Penguins are aquatic flightless birds predominantly found in the Southern Hemisphere, from Antarctica’s icy coasts to warmer regions like the Galapagos Islands. They vary significantly in size, from the 4-foot tall, 88-pound Emperor penguin to the small Little Blue penguin, which stands just over one foot tall and weighs 2-3 pounds. Their flipper-like wings are adapted for swimming rather than flying.
Why Some Birds Don’t Fly
The inability to fly in these birds stems from physical adaptations and environmental pressures. A primary biological change is the reduction or complete absence of a keeled sternum, or breastbone. In flying birds, the keel provides a large surface for powerful flight muscles, so its absence means a lack of necessary muscle support for sustained flight.
The wings of flightless birds are typically smaller and less developed than those of their flying counterparts, often appearing vestigial. Their bones are also denser and filled with marrow, rather than being hollow, which adds weight and makes flight mechanically unfeasible. These physical changes reflect a trade-off where energy and resources are redirected from flight capabilities.
Environmental factors have played a role in flightlessness. On isolated islands, where many flightless species evolved, there was often an absence of terrestrial predators. Without the need to escape threats by air, the metabolically demanding cost of flight became a disadvantage. Losing the ability to fly allowed these birds to conserve energy for other survival functions like reproduction or foraging for abundant ground food sources.
Life on the Ground
Flightless birds have developed alternative strategies to thrive in their environments. Ostriches and emus rely on their legs, enabling them to run at speeds up to 45 miles per hour and 30 miles per hour, respectively. This speed is their primary defense against predators and allows them to cover vast distances across open landscapes.
Penguins have become specialized marine birds. Their wings have transformed into paddle-like flippers, allowing them to swim with agility and dive to considerable depths. They spend a large portion of their lives in the ocean, hunting fish and other marine life.
Nocturnal kiwis use their acute sense of smell and long bills to forage for underground invertebrates. They also dig burrow systems for shelter and have strong legs for navigating their forest habitats.
The kakapo, a ground-dwelling parrot, uses its legs for climbing trees and its small wings for balance or to “parachute” gently to the ground. Its moss-green plumage provides camouflage, blending seamlessly into the dense New Zealand forests. These adaptations demonstrate how flightless birds successfully occupy ecological niches without leaving the ground or water.