About 66-million years ago, a giant asteroid hit the Earth without mercy.
The ground-dwelling birds that survived would not have had an easy existence.
Ground-dwelling bird ancestors managed to survive, eventually taking to the trees when the flora recovered.
"Perching birds went extinct because there were no more perches", said Dunn.
"Only a handful of ancestral bird lineages succeeded in surviving the mass extinction event 66 million years ago, and all of today's wonderful living bird diversity can be traced to these ancient survivors", Field added.
If it hadn't struck our planet all those centuries ago, maybe we would have gotten to live out our Flintstones fantasies and would be flying giant birds instead of riding in killer automated cars. Lots of small-bodied birds today consume pests, and this quality can be traced to the enduring birds 66 million years earlier. Spores are much smaller than seeds, and they can easily grow in a damp area.
How birds survived asteroid strike wipe-out
A team of scientists found this by examining fossil plant remains and the ecological makeup of ancient and modern birds and they think it is due to the impact of the asteroid that decimated the forests all over the world that lasted hundreds and even thousands of years to be restored.
"This fern spike represents evidence of 'disaster flora, ' where pioneer species are rapidly recolonizing open ground, such as seen today when ferns recolonize lava flows in Hawaii or landslides after volcanic eruptions", Bercovici says.
The project's pollen expert, Antoine Bercovici of the Smithsonian Institution and the Denver Museum of Nature and Science, helped determine that the world's forests were destroyed by looking at microscopic fossils of pollen and spores.
So the length of time would it take the ferns to prosper? "To date, there's really been no good empirical estimates on what temperature is doing following the impact, in terms of hundreds of thousands of years", says Page Quinton, a geologist at the State University of NY at Potsdam.
The researchers painstakingly searched for them in pounds of rock from El Kef, Tunisia, a site that is famous for having well-preserved rock layers that span the time periods both before and after the asteroid impact.
Studying whole paleoecosystems shows how life on Earth has evolved through all the trials and tribulations of the past, Dunn said in an email. Jingmai O'Connor, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology in China said, "Forest loss was only one of several factors working in combination that determined which bird lineages survived". "It's possible that, if this sort of logging continues unabated, it will leave an enduring signature on the advancement of birdlife". "They're these millimeter or half-millimeter long little teeth, and under the microscope they are gorgeous", says MacLeod, adding that they also find tiny fish scales or bits of bone. "We need to take these lessons to heart and act now to preserve today's profound biodiversity".