Why Can’t Some Birds Fly?…… Though the common ancestor of all modern birds could fly, many different bird species have independently lost their flight.
The cassowary is one of approximately 60 living species of flightless birds. They include some species of duck and all species of penguin, secretive swamp dwellers and speedy ostriches, giant emus, and tiny kiwis.
Flight can have incredible benefits, especially for escaping predators, hunting, and traveling long distances. But it also has high costs: it consumes huge amounts of energy and limits body size and weight. A bird that doesn’t fly conserves energy so it may be able to survive on a scarcer or less nutrient-rich food source than one that flies.
When a bird species don’t face specific pressures to fly, it can stop flying in as quickly as a few generations. Then, over thousands or millions of years, the birds’ bodies change to match this new behavior. Their bones, once hollow to minimize weight, become dense. Their sturdy feathers turn to fluff. Their wings shrink, and in some cases disappear entirely.
Most often, flightlessness evolves after a bird species flies to an island where there are no predators. As long as these predator-free circumstances last, the birds thrive, but they are vulnerable to changes in their environment.
Most of these birds, like emus and ostriches, ballooned in size, weighing hundreds of pounds more than wings can lift. Their legs grew thick, their feet sturdy, and newly developed thigh muscles turned them into formidable runners.
Though they no longer use them to fly, many of these birds repurpose their wings for other means. They may be flightless, but they’re still winging it.
Enjoy the video for further understanding:
Categories: Plants & Animals.