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New Zealand's Giant Eagle Showed Rapid Size Gain

Huge eagles 'dominated NZ skies'

One of the largest birds of prey ever recorded, an extinct giant eagle,
was once New Zealand's chief predator, DNA evidence from fossil bones
The researchers, led by Professor Alan Cooper from Oxford's Ancient
Biomolecules Centre, extracted DNA from fossil eagle bones dating back
about 2,000 years.

Dr Michael Bunce, who carried out the research, said: "When we began the
project it was to prove the relationship of the Haast's eagle with the
large Australian wedge-tailed eagle.

"But the DNA results were so radical that, at first, we questioned their

What they showed was that the New Zealand bird was in fact related to one
of the world's smallest eagles - the little eagle from Australia and New
Guinea, which typically weighs less than 1kg (two pounds).

Yet the Haast's eagle weighed between 10kg (1st 8lb) and 14kg (2st 3lb) -
between 30% and 40% heavier than the largest living bird of prey alive
today, the harpy eagle of Latin America, and was approaching the upper
weight limit for powered flight. 

 Dr Bunce said: "Even more striking was how closely related genetically
the two species were. We estimate that their common ancestor lived less
than a million years ago.

"It means that an eagle arrived in New Zealand and increased in weight by
10 to 15 times over this period, which is very fast in evolutionary terms.
Such rapid size change is unprecedented in birds and animals."

Dr Richard Holdaway, a palaeobiologist at the University of Canterbury,
said: "The size of available prey and the absence of other predators are,
we think, the key factors driving the size increase. The eagles would have
been able to feed unhindered on their kill."

No other predators allowed this dinosaur - er bird to reach large size?
Interesting relationship. How general is that?