Bird numbers have been monitored for more than 26 years and yellow-crowned parakeet numbers have tripled on last year.
Department of Conservation (Doc) principal scientist Colin O’Donnell, who has been involved since the start of monitoring, said bird life had flourished, with counts of most native species steadily increasing.
"All native birds were predicted to decline without intervention but regular use of aerial 1080, combined with extensive trapping, has turned their fortunes around," he said in a statement this week.
"Mohua/yellowhead were heading towards extinction at this site but since 2018 have been the most commonly counted bird."
Mohua have increased from a low of 14 in 1991 to 479 counted in the 350ha study area in 2023.
"The Landsborough is now a stronghold for this threatened species."
The spike in yellow-crowned kākāriki was due to the beech forest seeding (a mast) fuelling a prolific breeding season in 2023, Dr O’Donnell said.
"When food is plentiful, kākāriki can keep breeding from late summer right through the winter and have up to three nests with an average of five chicks per nest.
"However, as tree hole-nesters and with noisy nestlings, kākāriki are also a target for stoats and rats."
Beech masts are also a bounty for rats, mice, and stoats which feed on the rodents.
Rising predator numbers in the Landsborough Valley last year triggered the start of an aerial 1080 predator poisoning operation in January this year.
It reduced rats to undetectable levels and would have knocked down stoats and possums.
The outcome for native birds will not be known until the next bird count this coming spring.
Predator control began in the valley in 1994 and has since expanded to include extensive trapping and aerial applications of 1080.
The Landsborough bird count is Doc’s longest dataset monitoring bird populations through repeated aerial 1080 applications. Since monitoring began native bird numbers have more than doubled, while introduced birds have halved, most probably due to increased competition from native birds.
The Doc team spends several days in early summer each year, doing five-minute bird counts at 112 stations in the Landsborough Valley.
Upward trends were recorded for nine native bird species.
Counts for tomtit, kea, New Zealand falcon, kererū and shining cuckoo have remained more or less stable or are increasing at a very slow rate.
Two species — silvereye/tautou and long-tailed cuckoo/koekoeā — have declined.
