By ANNE BESTON environment reporter
Reaching adulthood might be a struggle against the odds for our national bird, but given half a chance, kiwi are big winners in the longevity stakes.
The birds are one of the longest-living feathered species in the world. New research shows average life expectancy for adult kiwi
is around 50 years, with an upper limit of 100.
"Before we started our research people thought they lived 20 to 30 years, but without predators they have an exceptionally long life," said Department of Conservation scientist and BNZ Kiwi Recovery Programme co-ordinator Dr Hugh Robertson.
The age statistics are provided by long-running research projects at Westland's Okarito Forest and at Kapiti Island, havens free of dogs and ferrets that kill adult kiwi.
The rare rowi kiwi at Okarito, numbering around 200 adults, and little spotted kiwi at Kapiti Island, population more than 1000, have a life expectancy of around 39 years.
Each bird is tracked and age estimates are revised upwards or downwards according to how many are still alive.
Proving how long kiwi live is difficult because no one is sure of the age of the birds that were first banded 25 years ago. But estimates will become more accurate within the next decade.
"Just in the last year or two it's become obvious some of these populations like Okarito are pretty amazing and it's not just that some individuals are getting a good run, it's that kiwi are much-longer lived than we first imagined," said Dr Robertson.
But in places such as Northland, where dogs and ferrets kill kiwi in the wild, the average adult life expectancy is just 12 years.
Bird life
Average life expectancy for:
House sparrow - one to two years.
Bellbird - eight-plus.
Takahe - 14 to 20 years.
NZ's oldest banded mallard is 26 years.
Conservation and Environment
Herald Feature: Conservation and Environment
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