London, May 25 (IANS): The asteroid that killed dinosaurs 66 million years ago, also led to the extinction of the first tree-dwelling birds, finds a study.

The asteroid that crashed to Earth with a force one million times more than the largest atomic bomb decimated the planet's forests as well as its canopies.

With no more perches, the perching birds went extinct. The ones that are alive today are descendants of a handful of ground-dwelling species, like modern ground birds such as kiwis and emus, the researchers said.

"The temporary elimination of forests in the aftermath of the asteroid impact explains why arboreal birds failed to survive across this extinction event," said lead author Daniel Field, from the Milner Centre for Evolution at the University of Bath, UK.

"The ancestors of modern arboreal birds did not move into the trees until forests had recovered from the extinction-causing asteroid.

"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," Field added.

The study, appearing in the journal Current Biology, determined the destruction of the world's forests, by looking at microscopic fossils of pollen and spores.

The fossil record immediately after the asteroid hit shows the charcoal remains of burnt trees, and then, tons of fern spores, the researchers said.

"Our study examined the fossil record from New Zealand, Japan, Europe and North America, which showed there was a mass deforestation across the globe at the end of the Cretaceous period," said Antoine Bercovici, pollen expert at the Smithsonian Institution and the Denver Museum of Nature and Science.

With no more trees, the tree-dwelling birds went extinct. The birds that did manage to survive were ground-dwellers -- birds whose fossilised remains show longer, sturdier legs like we see in modern ground birds like kiwis and emus.

Though the dinosaurs and their perching bird neighbours died 66 million years ago, their plight is relevant today, the researchers noted.

"The end-Cretaceous event is the fifth mass extinction -- we're in the sixth," Dunn said.

"It's important for us to understand what happens when you destroy an ecosystem, like with deforestation and climate change -- so we can know how our actions will affect what comes after us," Dunn noted.