The shy, nocturnal kiwi may have once strutted around in daylight before being forced to take the night shift by bigger rivals, according to scientists who have mapped the bird's DNA.
A study by researchers in Australia and Germany, has found the kiwi picked up many of its unusual traits - nocturnality, a strong sense of smell and colour-blindness - shortly after arriving in New Zealand about 35 million years ago.
They said it is believed the moa monopolised food sources during the day, forcing the kiwi to adopt an alternative nocturnal lifestyle.
In mapping the kiwi genome, the scientists also found the bird's unusual nostrils, at the tip of its beak - something more common on mammals - developed to give the kiwi an unusually strong sense of smell which lets it forage for food at night.
Other adaptations the kiwi picked up to survive at night include colour-blindness and the lowest metabolic rate among all birds.
University of Canterbury senior lecturer Tammy Steeves said although it was worrying the study had to be done outside of New Zealand, it would be useful in understanding the lifestyle of the kiwi.
"It should be helpful to those involved in conservation to know the underlying reasons for the special nature of the kiwi in that it has lost genes for colour vision and gained new abilities in smell," she said.
Te Papa genetics researcher Lara Shepherd said while the research was positive, protecting kiwi was the priority.
"This extensive new genetic data set won't stop the decline of kiwi in the wild - currently at 2 per cent per year - which is largely from predation by introduced mammals. New funding for kiwi predator control announced in this year's budget will hopefully halt this decline," she said.
The work is published in Genome Biology and was conducted by staff at the Max Planck Institute for Evolutionary Anthropology in Germany and Griffith University.
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