A Massey University post-mortem has found six kea in the Matukituki Valley of the Aspiring National Park ''are likely'' to have died from 1080 toxin.
The birds were among the 12 kea monitored by the Kea Conservation Trust after the Department of Conservation's aerial 1080 predator control operation on February 11.
DoC threats director Amber Bill said in a statement today it was ''regretful'' to lose any kea to 1080.
''But overall, aerial predator control is proven to benefit kea populations.
''It's upsetting and disappointing to lose six kea but we are confident with effective control of rats and stoats we will significantly boost nesting success and the number of young birds entering the population.
''We are concerned the tracked kea may have learnt to eat human food around the tramping huts, making them more likely to try 1080 cereal bait.
''DoC's extensive research of kea through aerial 1080 operations show the risk of 1080 to kea in remote areas is very low but increases markedly with birds that have learnt to scrounge for human food."
Bill said the Matukituki operation followed DoC's best practice to mitigate risks to kea from 1080 and ensure they benefited from stoat control after last year's extreme forest mast or seeding.
''We are constantly working to improve our risk mitigation standards for kea, which are informed by our ongoing research programme.
''In light of this incident, we will be investing more to explore potential additional measures that DoC can take to reduce the risk to kea in future 1080 predator control operations."
Bill said DoC was considering a campaign to discourage people from feeding kea and prevent kea from learning to scrounge.
"Kea are super smart and present unique conservation challenges.
''We need to continue to learn and assess all options to protect this national taonga from predators and other threats."
Recent rodent monitoring results from the Matukituki showed rats had been reduced from damaging levels - present in 47 per cent of tracking tunnels - to being undetectable - 0 per cent of tracking tunnels -, following the 1080 operation.
Stoat monitoring was underway.
The Matukituki programme was designed to protect rock wren, kea and whio, as well as kākāriki, kākā, and South Island robin following a beech mast-fueled rat and stoat plague.
Bill said DoC was monitoring whio and rock wren to track how these species were doing.
The dead birds were three adult males, one adult female, one juvenile male and one juvenile female.