Songbirds are so-named because they represent some of nature's greatest vocalists. Perhaps because of their superb communication skills, these birds have swept across the world, and are now found on every continent except Antarctica. They are, by far, the largest group of birds in the world today, with more than 5,000 species. That's nearly half of all avian species on Earth.
Now an extensive genetic survey of these diverse avian songsters has definitively pinpointed the place where they all first evolved: Australia. The research also describes in unprecedented detail how the first songbirds radiated out of Australia to eventually colonize the world, reports Phys.org.
"One of the challenges with deciphering songbird evolutionary history is that they diversified so rapidly that previous studies had a difficult time estimating the branching pattern of the songbird family tree," explained lead author Rob Moyle. "With advances in DNA sequencing technology, we were able to collect an unprecedented amount of DNA sequence data that helped clarify songbird relationships."
Understanding timeframes in the branching pattern of the songbird family tree also helps to explain their geographical distribution, because the Earth's geography has changed dramatically since songbirds first appeared. Tens of millions of years ago, the continents were in different places and sea levels exposed or submerged different landmasses that could have acted as stepping stones for the birds to travel between continents.
For instance, previous theories have suggested that songbirds first traveled beyond Australia via islands in the Indian Ocean, until they reached Africa and, eventually, the rest of the world from there. But the new research presents a different take. It suggests that the age of songbirds is actually "about half" of what previous theories assumed, which means those Indian Ocean islands would have been submerged at the time of songbird radiation out of Australia.
The new model therefore proposes that songbirds first radiated out of Australia via the proto-islands that eventually became the modern island of New Guinea and the Indonesian archipelago, and spread to the rest of world via Southeast Asia.
Even so, many of the major branches of songbird lineages began their diversification in Australia, before they moved elsewhere, the research suggests.
Biologically, Australia is already a fascinating place, home to the vast majority of the world's marsupials and, even, egg-laying mammals. Now it seems that nearly half of all modern species of birds hail from the continent as well.
Next time you're romanced by the melodic tweet of a songbird, consider it a reminder of just how evolutionarily powerful that simple ability to sing is. It's an ability that has propelled a small group of charming birds from Australia to nearly every corner of the world.