Spring in the Makarora Catchment – From Ridge to River

Coffee break at Jumboland airstrip (the Coru Lounge)

With this seasons work programme in full swing, spring 2019 marks the installation of ABT’s upper river predator control for whio or blue duck (Hymenolaimus malacorhynchos) protection within the Siberia Valley and the Wilkin Valley. This follows previous walkover survey work with the aid of a protected species dog specifically trained in the detection of whio; New Zealand’s ancient waterfowl species, an important part of Makarora’s indigenous taonga.

A whio pair (also known as blue duck) recorded within the Wilkin Valley Feb 2019

Here remnant populations of whio still remain however numbers are low and fledgling survival is limited by the presence of invasive predators such as stoat and rat. This can often lead to a sex ratio imbalance as females tend to be more vulnerable when nesting and during moult. The new trapping networks join up with alpine trap lines to help extend invasive predator coverage for this globally endangered species.

Predator control traps delivered by Backcountry Helicopters into mid-Siberia Valley. Photo credit Pilot Blair

Spring is also the time to resume alpine predator control operations for rock wren and kea protection. New traps added and a number of stoats, and rodents had been caught over the winter months despite not all traps being accessible at higher levels due to the amount of snow still present (these traps will be serviced next visit).

Invasive mammal trap exposed from the snow at Upper Lucidus (September 2019).
A mummified stoat caught at altitude during the winter months

Rock wren pairs were active at the Crucible Basin but all was quite in the upper Wilkin Valley (where snow cover heavier) suggesting that this population may not of yet stired from their winter torpor. Kea were heard calling above the Siberia Valley  and one in the upper Wilkin.

Crucible Basin trap drop off with Backcountry Helicopters and logistical planning for the day ahead
Snow cover along the ridge of Lake Crucible looking towards Gillespie Saddle (Oct 2019). The characteristic call of the rock wren is often heard here.

Back in the lower river valleys of the Makarora and Wilkin, braided river birds have returned and are starting to nest again. ABT braided river invasive mammal predator control continues on a monthly basis throughout the year with the help of regular volunteers. Stoats, rats, hedgehogs and feral cats are being reduced to help improve fledgling success of endangered birds such as black-fronted tern, wrybill and black-billed gull. The Southern black-backed gull is a avian predator of endangered braided river birds and their chicks. Adaptive management of this species is due to progress this season also.

Makarora braided river habitat showing the Wilkin confluence and the head of Lake Wanaka

Acknowledgements

With thanks to all our volunteers, funders, partners and supporters 🙂

Alpine predator control progress – winter activity indicated

Since the installation of ABT’s alpine predator control programme for the protection of rock wren Xenicus gilviventri, stoats have been recorded in traps at 1200 m elevation (refer to spatial distribution map below) in areas of rock wren habitat and they are still being caught during the winter months.

Adult male stoat caught at 1200 m by DOC 150 (kea proof) trap.

During this winter, Celium remote monitoring technology has shows that invasive mammalian predators are still on the move during the winter and are being caught within the alpine environment where indicative rock wren territories have been identified.

Snap shot of ABT trapping data Feb – April 2019 for Castallia/ Lucidus

The real time data shows current available trap coverage at Lucidus/ Castalia on 8 August 2019 is mostly reduced at lower altitudes and representing a threat to rock wren territory (southern scree area above Lake Lucidus). The red symbols display trap triggers and the green symbols identify the remaining trap coverage available to passing predators. The data illustrate that there is currently no imperative to replace bait (probably due to low temperatures in the alpine environment or lack of predator food source), and that servicing requirements are only determined by available un-sprung trap coverage at this stage (potentially effective rock wren protection).

Real time data provided by Celium remote monitoring technology.

The Celium remote technology provides additional information on alpine predators such as commuting activity and time of capture. Most trap triggers appear to occur at dawn between 06:00 – 08:00 h at 1000 to 1200 metres.

Time and altitude of invasive mammal trap triggers and previous trap servicing occasions

Climate conditions are recorded showing decreasing daily temperatures towards winter at all three Hub Stations. Overall winter conditions are cooler at Castallia/ Lucidus relative to the Crucible Basin.

Celium Hub Station daily temperatures at three alpine locations.

We look forward to servicing alpine traps and resuming rock wren monitoring this coming season, once baseline temperatures have warmed up and the rock wren are out of their winter torpor. Hope to see this juvenile from last year!

Last years (2018/2019) rock wren fledgling

Acknowledgements

With thanks to all our volunteers, partners and the following funders; WWF, the Tindall Foundation, Otago Regional Council, Oceana Gold and the Otago Community Trust.

References

O’Donnell, C F J, Weston K A, Monks J A. (2017). Impacts of introduced mammalian predators on New Zealand alpine fauna. New Zealand Journal of Ecology 41: 01-22.

Weston, K A, O’Donnell C F J, van Dam-Bates P, Monks J M (2018). Control of invasive predators improves breeding success of an endangered alpine passerine. International Journal of Avian Science. Vol 160, Issue 4.