Rock wren numbers better than expected
New Zealand’s only true alpine bird is more widely spread in the Mackenzie Basin than previously thought according to the most extensive survey programme in decades.
A group of 18 people surveyed nine sites looking for the ‘‘cryptic’’ and endangered rock wren in the Mackenzie Basin area as part of the Te Manahuna Aoraki project, a multi-agency predator control initiative which seeks to turn the area into a predator-free zone in 20 years.
Tracking the rock wren wasn’t an easy task according to Te Manahuna Aoraki spokesperson Robyn Janes.
‘‘They climbed over mountain tops, rocky cliffs and boulder basins searching for the endangered bird.
‘‘Rock wren are cryptic and hard to spot as they hide in big boulder fields. Males are more vibrant, while the females are a paler brown.
‘‘The survey team made two trips, they would walk into an area, listen for the birds and then play calls to attract them.
‘‘It’s unknown how the tiny birds survive the harsh climate above the tree line all year round. It is likely they continue to forage on rocky bluffs where snow has not collected and among large boulder fields.’’
Te Manahuna Aoraki project manager and DOC biodiversity ranger Simone Cleland said there was a big information vacuum about rock wren populations and their current range and the survey has provided a current snapshot in time.
‘‘The teams were delighted to find the birds are still persisting at seven of the nine survey sites.
‘‘The reality was we were prepared not to find any rock wren so it was really exciting to see them across a range of sites,’’ Cleland said.
‘‘This is great news as rock wren can become extinct quite quickly, site by site as they are poor fliers and nest in holes on the ground, makes them easy prey for stoats.’’
This is the most comprehensive rock wren survey undertaken in the project area since the 1980s.
While the Department of Conservation have surveyed for rock wren/ tuke at Aoraki/Mt Cook in two recent years, this search also involved the Ben Ohau range, Beetham and Godley Valleys, and Whale Stream areas.’’
Cleland said rock wren were still in low numbers, with approximately 50 seen in the survey.
‘‘What was positive was we saw family groups with fledged juveniles.
‘‘In summer, when the avalanche risk has lessened, Te Manahuna Aoraki are planning to extend trapping networks into areas of rock wren habitat.
‘‘The information from the survey will help us decide where best to put the new trap lines.
‘‘Rock wren respond extremely well to predator control so we hope the new trap networks will have a positive impact on rock wren survival quite quickly. They’re such a hardy little bird.’’
DOC Science Advisor Kerry Weston said prior to the 1980s, Aoraki/Mount Cook National Park was considered a stronghold for the birds, with rock wrens commonly seen around the parks more popular walking tracks.