Ichthyornis dispar was a primitive seabird with teeth that lived during the late Cretaceous Period – from 100 million to 66 million years ago – in North America. Courtesy of Michael Hanson and Bhart-Anjan S. Bhullar.

After the asteroid struck Earth long ago, all birds with teeth went extinct. But many of the toothless ones kept living. Some scientists think not having teeth is what allowed these birds to survive^[8].

Fossils of early toothless birds show they were able to eat more plant-based food^[9] – specifically nuts, fruits and seeds. This meant they relied less on eating other animals than birds with teeth did. Some scientists think this difference in diet became a big advantage after the asteroid impact.

When the asteroid struck Earth, it immediately caused massive tsunamis and earthquakes^[10]. A giant pulse of heat from the impact caused enormous wildfires near where the asteroid hit. In the months that followed, huge amounts of dust filled the layer of air that surrounds Earth. It blocked the sun, making less light available for plants to grow^[11].

For animals that ate plants, there was much less food. Many went extinct, which spelled trouble for the animals that ate them.

Since so many animal species died – and plants were struggling to get enough sunlight – food would have been hard to find if you were a bird. But if you could peck the ground and find buried seeds or nuts to eat, that might have made all the difference in your ability to survive as a species^[12].

How science works

Of course, it’s possible other factors caused toothless birds to survive while their toothy cousins perished – including luck.

For now, it’s a mystery with no definite answer. This is how science works. Scientists formulate ideas or hypotheses using existing knowledge and information. Then they test their ideas – either by conducting experiments or by gathering more evidence. This information either supports or disproves their ideas.

So the scientists who study bird evolution are ready to revise the story of how birds made it and dinosaurs didn’t as they collect more information from rocks, fossils and ancient DNA^[13].

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com^[14]. Please tell us your name, age and the city where you live.

Authors: Chris Lituma, Assistant Professor of Wildlife and Fisheries Resources, West Virginia University

Read more https://theconversation.com/how-did-birds-survive-while-dinosaurs-went-extinct-197185

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