Asteroids impacts, which have taken place time and again on earth, scarred the surface of the blue planet, leaving behind giant craters. One of the biggest and most famous asteroid impact events is the one that took place some 66 million years ago, which is the end of the Cretaceous period and the beginning of the Paleogene period (Cretaceous-Palaeogene). Measuring about 10 to 15 kilometers in diameter, the asteroid or the Chicxulub impactor, hit the earth leading to several environmental changes. It caused wildfires, acid rain, protracted darkness, and a global cooling (as low as 14 to 18 degrees Fahrenheit) that made the earth an inhospitable place to live in. The impact also led to the extinction of numerous plant and animal species, including non-avian dinosaurs.
The Cretaceous-Palaeogene or K-Pg event is an important one because it marks the period of creation as well as destruction. Much of Earth’s biodiversity that exists today including birds, mammals, marine fishes, and frogs arose rapidly following this event. According to recent research, the ground-dwelling birds made it through the planet-altering catastrophe, going on to be the ancestors of all the birds that exist today.
“Today, birds are the most diverse and globally widespread group of terrestrial vertebrate animals – there are nearly 11,000 living species,” said Daniel Field, lead study author and evolutionary paleontologist at the University of Bath’s Milner Centre for Evolution. “Only a handful of ancestral bird lineages succeeded in surviving the mass extinction event 66 million years ago, and all of today’s amazing living bird diversity can be traced to these ancient survivors.”
So, how did the birds manage to survive this difficult phase of Earth’s history? Well, we know that smaller animals tend to be better at surviving mass extinctions. This is because they are more in number and need less food. Hence, smaller birds had an evolutionary advantage. Scientists performed a statistical study of the ecological habits of birds existing at present to find out if their ancestors were more likely to live in trees than on the ground, a process known as ancestral ecological reconstruction. The study showed that the birds that survived the K-Pg mass extinction event, were certainly ground-dwelling and thus the ancestors of all birds living today.
A prominent avian casualty of the Cretaceous-Palaeogene event was a group known as the opposite birds, the most abundant bird-like creatures existing prior to the devastating K-Pg event. Though they were large in numbers during the age of dinosaurs, opposite birds went extinct altogether following the K-Pg event, probably because they tended to live in trees.
Following a study of the hind limbs of bird fossils left after the K-Pg event, it was found that several bird groups that today are known as tree dwellers probably had ground-dwelling ancestors that didn’t have the perching abilities of their descendants. This supports the fact that several groups of birds from this time evolved to move into the trees repeatedly and independently.
The study tells us that even if many modern birds make their homes in the trees, the ancestors of all tree-dwelling bird groups moved there from the ground up.
Researchers shared these new findings in a study published in the journal, Current Biology.