Nevertheless, the biggest bird you’ve never seen is the closest cousin to the wee, flightless kiwi, according to new DNA evidence. Surprised? So was study co-author Alan Cooper.
“Geographically, it didn’t make any sense. Morphologically, it didn’t make sense. Ecologically, it didn’t make any sense,” Cooper told Ed Yong.
But data doesn’t lie. Cue the collective sigh of relief from New Zealanders, who for the past two decades have been under the false impression that their national bird was an immigrant from—heaven forbid—Australia.
But if the kiwi didn’t descend from Australia’s emus, how did they get to New Zealand? The kiwi and elephant bird are both part of a group of flightless birds called ratites, which are scattered around the world’s southern continents. (Also in the club: African ostriches and South American rheas.) Up until now, scientists assumed the ratites were already flightless by the time their ancient super-continent broke apart 130 million years ago, leaving them isolated on their respective landmasses.
But the close genetic link between the kiwi and Madagascar elephant bird suggests a different narrative. As researcher Kieren Mitchell explains,
"If the common ancestor of kiwi and elephant birds lived on Madagascar, then kiwis must have flown to New Zealand. If this ancestor lived on New Zealand, then elephant birds must have flown to Madagascar," Mitchell said. "Or perhaps the common ancestor of both elephant birds and kiwis flew to their final locations from somewhere else entirely."
But this seemingly solved mystery leaves more unanswered questions in its place. For instance, if the kiwi’s diminutive stature is closer to its original partridge-sized flighty ancestor, rather than the result of gradual shrinking, why does it lay such disproportionately large eggs?