The ostrich is one of the largest birds in the world – that’s something we all know quite well. Yet when it comes to understanding why ostriches can’t fly, that’s a bit less understood. In this post, we’ll tell you what you need to know about these large flightless birds.
What You'll Learn Today
How Did Ostriches Evolve to Not Fly?
The ostrich is the largest living bird on Earth and is one of several species in a group of birds known as ratites. All ratites, including emus, rheas, cassowaries, and kiwis, are flightless. There is only one exception to this group in the tiny species.
Ostriches cannot fly because, like all ratites, they do not have the keel portion of the sternum (also known as the breastbone). The keel attaches to the stronger pectoral muscles that are typically used for flight.
This might seem obvious to you when glancing at an ostrich – after all, it has teeny tiny wings and a huge body! But what is the evolutionary purpose of this?
Scientists aren’t exactly sure why ostriches evolved to become flightless. However, one theory is that the largest ancestors of the ratites, including the massive elephant bird, evolved after the dinosaurs went extinct but before most mammals came about.
Because of that, these large ratite birds would have had no real predators. With very few threats to contend with, they could more or less do as they pleased, existing as large, flightless birds.
Of course, there are plenty of mammals (such as lions) who consider an ostrich a tasty meal now – the days of having no predators have unfortunately come to an end for the flightless ostrich.
However, they have evolved the ability to run very quickly with powerful leg muscles, helping them to compensate for their inability to fly.
This is all done through the ability of regulatory DNA. Regulatory DNA is involved in regulating when and where genes are turned on and off. Major evolutionary changes, according to some researchers, occur because mutations to protein-making genes were tied to this trait or because there were tweaks to more mysterious regulatory DNA.
Did Ostriches Use to Fly?
Technically, no – the ostrich as we know it has always been a large, flightless bird.
However, this concept of regulatory DNA as well as basic evolutionary science suggests that ostriches may have close relatives that could fly.
In the past, scientists believed that all ostriches, along with other ratites, shared one flightless ancestor that lived on a supercontinent called Gondwana back in the Cretaceous period. As the supercontinent broke up, the ratites were separated out to various continents and then later evolved into all the flightless birds we know about today (ostriches, emus, kiwis, etc).
However, recent discoveries have rendered this theory incorrect. After DNA was extracted from a bird that lived on the island of Madagascar – a bird named the “elephant bird” – it was closely linked to birds in the ratite bird. In fact, its closest relative was the kiwi.
There’s no way to get from New Zealand, where the kiwi is found, to Madagascar without flying – so the current theory is that all ratites had flying ancestors like the elephant bird.
And isn’t that a scary thought – the ostrich or a bird even larger than the ostrich taking to the skies!
The Ostrich DNA Story
Scientists still aren’t totally clear on the story behind ostrich flight and the DNA of this species, along with the evolutionary story of all ratites.
Why are they all flightless, with the exception of the teeny-tiny tinamous?
One speculation is that a common ancestor lost the ability to fly, but again, this has been mostly disproven with the discovery of the elephant bird. Instead, it is now more widely believed that the changes to regulatory DNA simply turned off the ability for the bird to fly – it’s somewhat of a “use it or lose it” hypothesis.
Ostriches, kiwis, emus, and other flightless birds weren’t using their ability to fly – so they lost it over time.
There are no known examples of a bird species regaining the ability to fly once it’s been lost, so don’t worry – you aren’t likely to see ostriches suddenly learning how to fly once again.
Which Birds Cannot Fly and Why?
As we’ve mentioned in this article, ostriches can’t fly – plain and simple. But what about other birds?
In the flightless group of ratites, you will also find rheas, cassowaries, kiwis, and emus. All of these birds have flat breast bones with no keel to anchor to the strong pectoral muscles they need to fly.
Plus, in the case of large birds like emus and ostriches, their large bodies would be far too heavy for their tiny wings to lift off the ground, anyway.
However, there are other birds outside of the ratite family that can’t fly, either. These include penguins, steamer ducks, takahes, kakapos (also known as owl parrots), and several others.
The penguin, perhaps the most ubiquitous of all these birds, cannot fly because of its body composition. These birds are short and stocky, better built for swimming and diving than for flying – which is fine, because that’s what they spend most of their time doing, anyway!
Three out of four species of steamer duck are flightless – mostly because they’re too heavy to achieve liftoff. They don’t need to fly, since they run quickly and are extremely aggressive (in fact, some aggressive steamer ducks have been known to get in epic, bloody battles and to kill birds twice their size in these fights!).
Can Ostriches Glide?
Ostriches can’t fly – we know this.
However, if you’ve ever seen an ostrich run, you might be wondering what other capabilities these elegant, massive birds might have. Just check out this video for proof:
Although it can run at top speeds of close to 50 miles per hour, making it seem as though it’s flying by, it’s not actually taking to the air. It has a long, elegant stride that helps it to make quick, efficient work of any distance.
Once an ostrich gets going, it can run fast and may appear as though it is gliding through the air as it flaps its wings. However, real ostriches cannot fly, and despite what it looks like, it’s not really gliding, either. It’s simply running and flapping its wings!
Ostriches can’t fly, and for good reason. However, with everything else that these birds have going for them, do they really need to?