The biggest bird in history might have been blind as a bat

The giant elephant bird foraged at night in the forests of Madagascar, despite the fact that likely could barely see
The extinct giant elephant bird of Madagascar was flightless, blind and nocturnal. (John Maisano, University of Texas at Austin)
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Researchers studying the massive elephant bird of Madagascar have concluded that the part of its brain that was devoted to sight was tiny, and so it likely had terrible vision.

New research by Christopher Torres, a PhD candidate in the Department of Integrative Biology at the University of Texas, Austin suggests that this means the extinct elephant bird was likely nocturnal.

The largest bird known to science

The elephant bird lived on Madagascar up to about 500 years ago before it went extinct. It was the largest bird known to science. It was up to 4 metres tall and weighed anywhere between 300 and 600 kilograms. It is part of the same family of birds as the emu, ostrich, cassowary, and kiwi, its closest living relative today. The chicken sized kiwi is a flightless and nocturnal bird found only in New Zealand. 

New Zealand's kiwi bird is the closest living relative to the extinct elephant bird. (Markanderson72, Creative Commons Attribution-Share Alike 4.0)

What it could and couldn't do

Naturalists assumed that the elephant bird shared similar lifestyle traits to the birds it closely resembled, the emu and ostrich for example. They are flightless like the elephant bird, active during the day and have good eyesight, as many birds do.

But when Torres and his team digitally recreated the elephant bird brain, they found that comparisons to the kiwi were the most accurate despite the vast difference in size. In both the kiwi and elephant bird the the optic lobe - the bundle of brain nerves that control vision - is very small. From this they concluded that the elephant bird had rudimentary vision, just like the kiwi.

They also hypothesized that because the kiwi and elephant bird both had weak vision and were flightless and have similar brain construction, the elephant bird was also likely to have been nocturnal. Researchers say they did not expect to find that 500 years ago this giant bird was crashing around the forests of Madagascar with little or no vision at night.