The Landsborough valley
Image: Neil Sloan | ©


Thanks to more than 20 years of trapping and aerial 1080 treatment, native birds are flourishing in the remote South Westland valley.

In one of DOC’s longest studies, native birds were found to have more than doubled in number after more than over 20 years of sustained predator control in the Landsborough valley in South Westland. 

Predator control began in the Landsborough valley in 1994 after the impact of predators on birdlife was observed. Since then DOC has done valley-wide trapping and seven aerial-1080 operations timed with increasing rodent levels.

The most recent three 1080 operations covering the entire valley were in:

  • 2014
  • 2016, and
  • 2019.

Bird counts

Watch our video to discover how we monitored these native birds

To measure the effects of pest control DOC scientists have tracked the birdlife in the valley since 1998. This research involves a team of bird call experts doing approximately 175 ‘five-minute bird counts’. Each spring at fixed points in the valley, the team complete and record their counts which provide an index of relative bird numbers.

Learn about bird monitoring in the Landsborough valley on our blog

The results show that native bird numbers have more than doubled since pest control began. Most of the 13 different native bird species monitored increased but some remained stable or decreased as outlined below.

Mohua up from 14 to 485 birds

One of the most threatened birds in the monitoring area, mohua (yellowhead) numbers have increased more than 35-fold since predator control began. 

Species populations

Total native bird numbers doubled over the more than 20-year study.

These species showed a steady increase:

  • Yellowhead/mohua 
  • Tūī
  • Bellbird/korimako
  • Brown creeper/pīpipi
  • rifleman/tītitipounamu
  • Grey warbler/riroriro
  • Yellow-crowned parakeet/kākāriki 

These were stable when they would have otherwise declined:

  • Kākā
  • Fantail/pīwakawaka
  • Tomtit/ngirungiru
  • Wood pigeon/kererū

These species are competing with species that are now recovering.

These species declined:

  • Silvereye/tauhou
  • Long-tailed cuckoo/koekoeā

Silvereye are being outcompeted for food by more aggressive nectar-eaters such as tuī. Long-tailed cuckoo migrate to the Pacific islands each winter and may be affected by conditions there. They also rely on mohua and brown creeper to raise their chicks.

Numbers of introduced birds have also decreased. This is probably due to greater competition from more native birds.

View the 2012 published scientific paper (showing trends up to 2009)

Media releases

Back to top