The death of six kea in the Aspiring National Park last month is being attributed to 1080 predator poison.

The birds were being monitored by the Kea Conservation Trust in the Matukituki valley and were initially confirmed alive after the aerial 1080 predator control operation last month.

Massey University suggests 1080 caused their death after conducting post mortems.

The Department of Conservation says the deaths were regretful, but aerial predator control has a proven track record benefiting kea populations.

Threats director Amber Bill said the risk to kea from poison is very low in remote areas, but it increases where birds have learnt to scrounge for human food.