Oz import grew huge in NZ
Extinct Haast’s eagle linked to far smaller relative across ditch
Alost native species that was the world’s largest eagle — a massive bird that was big enough to prey upon 200kg moa in New Zealand’s prehistoric wilderness — actually had its roots in Australia, scientists say.
But it was only after it arrived here and underwent two million years of evolution that the Haast’s eagle, which boasted a 3m wingspan and claws the size of a tiger’s, became a global giant.
Scientists have long viewed New Zealand as a “Moa’s Ark”, a land mass that had been isolated since the age of the dinosaurs, protecting its unique fauna and flora from the rest of the world.
While that paradigm has been shown to be incorrect, the giant birds of prey, Haast’s eagle and Eyles’ harrier that called New Zealand home prior to their extinction shortly after human arrival, certainly helped to establish the picture of a primeval archipelago, lost in time.
At the top of the food chain in New Zealand, Haast’s eagle, the largest eagle in the world with a weight of up to 15kg, and Eyles’ harrier, the largest harrier in the world, had filled ecological niches that are on other land masses occupied by animals such as large cats or canines.
Until now, the evolutionary and biogeographic history of these island giants had long been a mystery.
The first molecular data from Haast’s eagle, which was published more than a decade ago, gave a first indication that things may be a bit more complex than they seemed.
“This molecular data suggested that Haast’s eagle was not closely related to other large eagles . . . but was in fact a close relative of the comparatively tiny, 1kg Australian little eagle, one of the smallest eagles in world,” explained Dr Michael Knapp, a researcher in the University of Otago’s Department of Anatomy and the lead author of a new study.
To add to the surprise, the molecular dataset indicated that genetically, at least for the very small subset of the genome that was analysed, Haast’s eagle was not very different from the little eagle.
In fact, they seemed to share a common ancestor sometime during the ice ages, a period of alternating cold and warm times which started about 2.5 million years ago and which we are likely still in today.
“The initial estimate for a common ancestor of Haast’s eagle and little eagle was about a million years ago,” Knapp said.
“On an evolutionary time scale, that is essentially yesterday.”
The new study analysed a significantly larger part of Haast’s eagle’s genome and is also the very first molecular analysis of Eyles’ harrier.
For Haast’s eagle, the study essentially confirms the earlier work, although the bigger dataset puts the age of the common ancestor of the Australian dwarf and the New Zealand giant closer to 2.3-2.5 million
years ago, at the start of the ice ages.
Curiously, the study found exactly the same story for Eyles’ harrier.
Its closest relative, as it turned out, is the small to medium-sized Australian spotted harrier, and they share a common ancestor at almost exactly the same time as the eagles.
Canterbury Museum natural history senior curator Dr Paul Scofield said these giant birds of prey went through some dramatic changes in a relatively short time.
“We’re increasingly finding [what] we see as iconic New Zealand species actually haven’t been here that long.”
The spectacular size increase of New Zealand’s birds of prey is likely a result of them essentially “climbing up” the food chain after arriving in New Zealand.