Flightlessness of a bird evolved twice

Birds on an island in the Indian Ocean evolved flightlessness twice “The flightless rail is descendent from a species of flying bird known as the white-throated rail (Dryolimnas cuvieri).

In the layers of rock immediately after the last inundation event, Julian found some more fossil bones. 'We found the leg bone of a rail in these deposits,' he says. 'But from that one bone we can see that it is already becoming more robust when compared to the flying rail, showing that the bird is getting heavier and so losing its ability to fly.'

This suggests that once the sea levels dropped again and Aldabra reappeared, the white-throated rail once again recolonised the islands and became flightless, giving rise to the modern birds we see today.

'There is no other case that I can find of this happening,' explains Julian, 'where you have a record of the same species of bird becoming flightless twice. It wasn't as if it were two different species colonising and becoming flightless. This was the very same ancestral bird.'”