31 August 2022
The world was a very different place during the Oligocene 35 million years ago. For one thing there was a big gap between Australia and Asia and songbirds’ ancestors could not leave Australia.
Then about 25 million years ago a land bridge formed when tectonic activity forced a patch of islands called Wallacea to the ocean’s surface. Wallacea, now part of Indonesia, bridged the gap and was the first step on the songbirds’ journey. (Ancient Wallacea in yellow below.)
They made the journey in flying steps, reaching the Western Hemisphere before Eurasia:
- Australia (label C below)
- Wallacea, an island group in Indonesia (label D)
- Southeast Asia and India (label E)
- Sub-Saharan Africa (label F)
- The Americas (label G)
Some songbirds were so successful that their DNA is found at each stop in living species across the world. Corvids are one such group.
Others, like waxwings (Bombycillidae), have few DNA traces to show the path they took. Waxwings’ living DNA relatives are found only in Wallacea, North America and northern Eurasia.
Learn more about songbirds’ amazing journey in these articles:
- How songbirds island-hopped their way from Australia to colonise the world and
- The original study: Tectonic collision and uplift of Wallacea triggered the global songbird radiation.
(blank world map from Wikimedia Commons. photo and remaining maps are credited in the captions, click on the links to see the originals)