Date:  28 August 2020

DOC has been monitoring birds in the lower Heaphy valley in Kahurangi National Park since 2015 to assess whether management is making a difference for wildlife.

Results show a trend of increasing numbers of nine native species — korimako/bellbird, pīwakawaka/fantail, riroriro/grey warbler, kākāriki/parakeet, toutouwai/robin, tauhou/silvereye, miromiro/tomtit, tūī and weka.

Rarer birds such as kārearea/New Zealand falcon, fernbird, kākā, and kea were only occasionally observed although there was a promising increase in kākā seen in 2019.

DOC Operations Manager Suvi Van Smit says the results are encouraging as intensive predator management in the Heaphy valley appears to be benefitting the local bird populations.

“It’s early days in this long-term biodiversity enhancement project but we are already seeing some native birds becoming more plentiful, confirming anecdotal reports from visitors to the Heaphy Track.

“We’ve increased the frequency of predator control in an area centered on the Heaphy valley since 2013 and have undertaken annual aerial 1080 predator control to suppress rats since 2016.

“Further monitoring is needed to be confident that increased predator control is causing the upswing in birdlife, but so far this appears to be the case.”

Korimako/bellbird was the most frequently detected bird. In 2015, 354 bellbirds were observed during five-minute bird counts at monitoring sites, increasing to 432 in 2019. Toutouwai/robin (26 to 63), kākāriki/parakeet (6 to 38), tūī (15 to 213) and weka (3 to 63) also showed notable increases over that time. A second survey method, distance sampling, produced similar results.

The 35-year project to enhance native wildlife in the Heaphy valley is funded from Bathurst Resources Limited’s 2014 compensation for the loss of biodiversity values from the Escarpment Mine operation on the Denniston Plateau.

The management area is about 29,000 ha with a core area of 13,000 ha including the mid-lower Heaphy valley and Iwituaroa Range, which is the focus of intense predator management. 

Due to the warm conditions in the lower Heaphy, rats breed and rebound more quickly than in upland areas. DOC monitors the effectiveness of rat control after each operation and results for this site have varied.

Last year’s results were disappointing with more rats surviving the operation than was desirable. This may have been due to the massive forest mast and very high rat numbers. DOC is doing research into these and other results as part of work to improve predator control regimes.

Localised possum control began in the Heaphy valley in the mid-1990s and was ramped up in 2007 with the first largescale aerial 1080 predator control operation over the management area. Subsequent operations occurred in 2012 and 2014 and annually since 2016. Further predator control is planned for 2021 as part of DOC’s Tiakina Ngā Manu programme.

Background

The Heaphy area of Kahurangi National Park has mixed beech, podocarp and broadleaf forest and is home to a wide range of native birds, roroa/great spotted kiwi, bats and threatened Powelliphanta land snails. Overall, 31 bird species were seen during five years of bird surveys, just eight of these introduced species.

Two different methods were used to monitor forest birds — five-minute bird counts and distance sampling. Birds were surveyed within six monitoring grids each with up to 25 sample points. The five-minute bird counts are used to record all birds heard in five minutes, while the distance sampling is a snapshot of birds’ presence and location, also within a five-minute period.

Read the bird survey report.

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