In one of DOC’s longest studies, native birds were found to have doubled in number after 20 years of sustained predator control in the Landsborough valley in South Westland.
Predator control began in the Landsborough valley in 1998 after the impact of predators on birdlife was observed. Since then DOC has done valley-wide trapping and six aerial-1080 operations timed with increasing rodent levels, with the most recent two, in 2014 and 2016, covering the entire valley.
To measure the effects of pest control DOC scientists have tracked the birdlife in the valley. This research involves a team of bird call experts doing 175 ‘five-minute bird counts’ each spring at fixed points in the valley, providing an index of relative bird numbers.
The results show that native bird numbers have doubled since pest control began. Most of the 13 different native bird species increased but some remained stable or decreased as outlined below.
Mohua up from 14 to 338 birds
Mohua (yellowhead) are now thriving in the Landsborough valley
Image: Sabine Bernert
One of the most threatened birds in the monitoring area, mohua (yellowhead), has increased in number 24-fold since the predator control began.
Total native bird numbers doubled over the 20-year study.
These species showed a steady increase:
- Mohua (yellowhead)
- Tūī (parson brid)
- Korimako (bellbird)
- Pīpipi (brown creeper)
- Tītitipounamu (rifleman)
- Riroriro (grey warbler)
- Kākāriki (yellow-crowned parakeet)
These were stable when they would have otherwise declined:
- Kākā (bush parrot)
- Pīwakawaka (fantail)
- Ngirungiru (tomtit)
- Kererū (wood pigeon)
These species are competing with species that are now recovering.
These species declined:
- Tauhou (silvereye)
- Koekoeā (migratory long-tailed cuckoo)
Koekoeā rely on mohua to raise their chicks, so will take longer to recover, while tautou are being outcompeted – for example by the much larger and more aggressive tuī.
Comments from Conservation Minister Eugenie Sage
“These results highlight that where we control pests over whole valleys and forests, we can turn around the fortunes of our native birds and help address our biodiversity crisis where 82 per cent of our birds are threatened or at risk of extinction.”
“The $181.6 million over four years of new funding in Budget 2018 will enable DOC to do more of this work and achieve great results for our birds.”