A female kakapo has been found dead on Whenua Hou or Codfish Island, west of Stewart Island.
The death of the young bird, named Ellie, reduces the total population of the critically endangered bird down to 125.
Kakapo Recovery rangers, who found her body last week, said there was no obvious sign of illness or injury.
A Conservation Services manager, Deidre Vercoe, said kakapo could live to be 60 so Ellie's death at 16 was a tragedy.
She said the loss was softened by the likelihood of a bumper breeding season ahead.
More than 25 chicks may be born because of rimu and beech masts due on Codfish and Anchor islands during the season, she said.