Ostriches are flightless today but their ancestors were ocean-crossing fliers, says new study

Ancient Flighted Birds May Hold Clues to Modern Flightless Species (Image: Canva)

Birds are usually praised for their capability to glide along the skies, but it has been found that the predecessors of today's flightless giants once engaged in skilled flight and covered long distances.

How did flightless birds end up on far-off continents?
Scientists have long been mystified about how huge, flying-capable birds such as ostriches, emus and kiwis wound up on far-flung continents like Africa, Australia, and South America. Long-held beliefs had their ancestors split apart by continental drift when the ancient supercontinent Gondwana began to fragment over 150 million years ago. However, fresh genetic data paint a different picture, postulating that these birds developed flightlessness much more recently.

What does the fossil evidence reveal about their past?
A group of scientists studied a relatively well-preserved fossil breastbone of one of the earliest flightless bird ancestors. In their research, as presented in Biology Letters, they found that these ancestral birds were capable of flying long distances, akin to contemporary pigeons and parrots. After reaching new continents, they gradually expanded in size and lost flight capabilities. This finding enlightens us about early bird dispersal over oceans prior to commencing terrestrial life.

Why did certain species abandon flight?
Specialists believe that two key reasons led to the loss of flight. When these birds were able to get enough food on the ground and had no serious predators, there was no evolutionary pressure to remain airborne. The extinction of large predators, such as dinosaurs, millions of years ago made them able to live without flight. They evolved special characteristics to survive over time, like strong legs for running or powerful kicks for defence.

What is still a mystery to scientists?
Although the research makes explicit the way flightless birds dispersed globally, it opens up fresh questions about their survival. Co-author and zoologist Helen James pointed out the enigma of how they survived given their reduced dispersal ability today. Most are now part of the clade Paleognathae, comprising ostriches, emus, cassowaries, and extinct giants moas and elephant birds.

Scientists think that learning how ancient birds learned to adapt to shifting ecosystems might shed more light on the process of evolution and survival. Their tale explains how flight, a once-unique characteristic, was ultimately exchanged for power, speed, and toughness on land.