The kea population in Nelson Lakes National Park appears to be under serious threat from possum predation, with the latest surveys suggesting that numbers of the alpine parrot have declined significantly in the past 10 years.
Last month, 50 researchers and volunteers from the Kea Conservation Trust and the Department of Conservation surveyed kea numbers at 90 sites in Nelson Lakes National Park, Arthur's Pass in Canterbury and the Borland Range in Fiordland.
Although the three-year study is being conducted mainly to compare populations between the three locations, kea numbers at Nelson Lakes appear to be much lower than those recorded in an earlier survey.
DOC researchers Josh Kemp and Graeme Elliott found that there had been a high level of kea nesting success at Nelson Lakes from 1993 to 1999. They identified 36 nesting sites, and also found that predation of the birds was low during the study period.
In contrast, only 12 kea were caught and banded at Nelson Lakes during last month's survey.
The researchers said it was also a concern that only three fledglings were seen during the 10-day observation period.
Mr Kemp said the main reason for the apparent decline in numbers was predation of kea eggs and chicks.
Possums were thought to be the main predator, because they lived in the same types of holes and crevices kea used for nesting, although stoats and rats also preyed on the parrots.
"There were possums in the vicinity of all the nest sites we surveyed this summer, and we saw possum sign and dead possums in some of the kea nests.
"The requirements for possums and kea nest sites are very similar, so we think the possums go in there to live and find the eggs and eat them -- they aren't actively seeking out the eggs."
The decline in kea numbers was consistent with an increase in the number of possums at Nelson Lakes, although more surveys were needed to reach a definitive conclusion, he said.
Tamsin Orr-Walker, of the Kea Conservation Trust, said lead poisoning of kea ingesting nailheads and flashings on buildings might also be a problem closer to settlements.
Although kea in other areas had been inadvertently poisoned by 1080 baits laid for pests, this wasn't a problem at Nelson Lakes, where 1080 poisoning in areas inhabited by kea was minimal, she said.
She said researchers were hoping to gain an insight into the reasons for the decline after fitting a satellite transmitter to a one-year-old kea and a fledgling at Nelson Lakes. Two adult females were also fitted with VHF transmitters to enable their progress during the next breeding season to be tracked.
She said researchers were also trying to develop a bird repellent for 1080 baits.
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