The Waipapa South kōkako survey, carried out in May 2023 by a team of 5 surveyors, covered 1250 hectares across 48 surveyor days.
The survey is the focus of a new report which has revealed 124 pairs of kōkako over the survey area – up from 87 pairs in the same area in 2015.
Comparisons between the two surveys reveal an average annual growth rate of 4% in the Waipapa South kōkako population over eight years.
The survey estimated 238 kōkako pairs in the wider Waipapa area, which brings the estimated number of kōkako pairs in pest control areas in Northern Pureora to 672 pairs.
DOC's Kōkako Recovery Group leader Rhys Burns says the increase in the birds' population is further evidence of the value of ongoing pest control over 30 years.
"DOC carries out ground pest control operations at Waipapa, targeting rats, one of the primary nest predators of kōkako," Rhys says.
"This is complemented by ground control operations in other parts of Northern Pureora undertaken by Howick Tramping Club, Auckland Tramping Club and Pirongia te Aroaro-o-Kahu Restoration Society.
"Together these pest control operations cover approximately 5730 ha of the forest – protecting the habitat the kōkako thrive in."
Ground-based predator control is complemented by DOC's National Predator Control Programme which delivers aerial 1080 operations - every three to six years - to target rats, possums and stoats over the wider 30,000ha Northern Pureora Forest.
Rhys says the combination of predator control efforts means the Northern Pureora Forest is now home to an estimated 25% of New Zealand's total kōkako population.
"The latest population estimate at Northern Pureora is the largest population recorded nationally since the kōkako recovery programme was started in the 1990s."
"The increasing Pureora population now also makes it more likely to be resilient to other more random factors such as major storms or a disease outbreak," Rhys says.
Continued pest control will ensure the kōkako population continues to increase, with numbers starting to get towards densities that were probably last present at this site in the 1950s or 1960s.
"The recovery of kōkako is a glimpse of what these forests used to be like before introduced mammalian predators arrived, and what it could be again in other forests if New Zealand can achieve widespread suppression or even eradication of mammalian pests in coming decades," Rhys says.
Graham Kimber, DOC's Maniapoto Operations Manager, says recovery of the kōkako population in Pureora is an important conservation success story for the area.
"Our team, working alongside mana whenua and our supporters, has put in a long-term effort to support kōkako in our district.
"There has been a lot of hard work on the ground to deliver this result.
"Hearing kōkako in the Pureora Forest is a really special experience and long-term recovery work means more people can enjoy the bird's song."
The 2023 Waipapa South block survey was undertaken by a team of between three and five surveyors, whose work involved walking grid transects between dawn and noon. Kōkako recordings were played at 200-metre intervals to illicit responses from the birds.
Kōkako are classed as "Threatened – Nationally Increasing", a classification that reflects their decline in extinction risk compared to previous decades, due to the combined effects of minimising habitat loss and controlling predators over their current 26 known populations.
