The Department of Conservation says the campaign to restore kakapo numbers has been held up by a shortage of rimu fruit.
Since 1995, under the Kakapo Recovery Programme, the population of the critically endangered nocturnal ground parrot - found only in New Zealand - has increased from 51 to 124.
Programme manager Deidre Vercoe says that the lack of rimu fruit on Codfish Island, off Stewart Island, and Anchor Island, in Fiordland, signals a non-breeding summer for the world's rarest parrot.
But in a way that's a relief, she says, because 2009 was the biggest breeding season ever, with 33 kakapo being born: "We're all quite exhausted from that," she says. "We had to hand-rear 26 of them."
Ms Vercoe hopes kakapo will breed again in 2011.