The Department of Conservation has released video footage of a possum killing and eating a young kea.
Researchers using nest-cameras have for the first time recorded attacks on defenceless kea nests invaded by stoats and possums in South Westland. Possums were known to kill adult kaka but for the first time have been filmed attacking the threatened species of native parrot, which only lives in forest and alpine areas of the South Island.
A large numbers of kea nests were failing in the wild, said DOC's Brent Barrett.
"We are just midway through the breeding season and of eleven nests we've had under surveillance three have been devastated by stoats and possums. That's a loss of six chicks.
"It was a grisly surprise to see photos of a possum eating a nearly fledged kea and video showing the prolonged and tormented death of chicks attacked by stoats," Mr Barrett said.
Nearly all the monitored nests were visited by possums, which meant there was a huge risk to the lowland populations of kea.
Mr Barrett said was distressing to discover that just how long it takes chicks to die during a prolonged attack by stoats.
One attack on two chicks lasted two and a half hours. One chick died at the end of the torment but the other lived for 40-hours with its injuries before disappearing.
The stoat predation footage was captured at a nest south of Fox Glacier and the possum was photographed in Okarito Forest.
Mr Barrett said photos and videos have been posted on YouTube under the key words "possums eat parrots" so that people could see exactly what was going on in kea nests.
Researchers are also monitoring trees for signs of excessive fruiting which would trigger a chain of events starting with a rat plague and ending with a plague of stoats.
"We are still in the process of gathering this information, but at the moment it looks like we may have a moderate rimu fruiting coming up," Mr Barrett said.