Monitoring the endangered rock wren within the alpine basins of the Makarora catchment

Focused on two alpine study sites; the Crucible Basin within the Siberia Valley and the Upper Lucidus/Castalia Basin within the north branch of the Wilkin Valley with extension into adjacent basins. Rock wren monitoring transects defined and surveyed initially for both sites during 2017/2018. The results of this survey work guided deployment of alpine invasive mammal traps and subsequent installation of Celium remote trap monitoring technology to improve predator control trap servicing efficiency and provide additional information on predator movements (first image above shows a male rock wren in moult, note abraided wing and tail feathers).

Following ABT’s initial rock wren monitoring transect surveys undertaken during summer 2017/2018 and observations during 2018/2019 breeding season ABT have now commenced colour banding of individual birds.

A newly colour banded rock wren at Lake Crucible

This bird monitoring method helps to identify individual birds, confirm rock wren territories and provide information on dispersal and survival of post-breeding juveniles whilst providing an indicator of predator control success. We can also learn about moult strategies for this unique alpine passerine.

Ornithologist Rachel Hufton taking morphological measurements during rock wren colour banding

Specialist mist nets are errected within know breeding territories and a audible lure is used to encourage individuals into the net. The mist net shelves are kept low as rock wren flight is limited and birds often forage close to the ground on terrestrial insects (spiders, moths, beetles and flies) and berries from low growing plants such as Muehlenbeckia axillaris (below).

Succulent fruits of Muehlenbeckia axillaris. Several rock wren have been noted foraging from this plant during February within the Crucible basin.

All birds are carefully extracted from mist nets by a NZNBBS certified bird bander. Three colour bands (two on the right leg, one on the left) are carefuly applied, biometric measurements taken and any observations on moult or body condition are recorded.

A mist net (9m) located within suitable rock wren habitat.

A combination of adult and juvenile birds have been banded during the 2019/2020 season. Images below show an adult male with a prominant supercilium and a weight of 14.6g. This bird appears to have gone through post-breeding moult (moulting is the periodic replacement of feathers by shedding old ones whilst producing new ones).

Male rock wren post- breeding moult (March 2020).
Rear of male rock wren showing new primaries and tail feathers.

 

 

 

 

 

 

 

 

This monitoring work provides addition information on rock wren in an area which has not previously been investigated at this level, complementary to existing study sites such as in Fiordland, and Haast, contributing to overall knowledge to promote effective future conservation management for this nationally endangered species. We look forward to further progressing rock wren monitoring during the next breeding season 2020/2021.

Rachel Hufton
The Crucible basin, one of the Makarora catchment alpine study site for the endangered rock wren. During December a haze of ash and dust from the Australian bush fires could be seen on the top of the lake.

ABT’s rock wren protection and restoration programme forms part of a broader threatened species project for the Makarora Catchment from “ridge to river” and is complementary to the Department of Conservation Predator Control Plan for Makarora as referenced within ABT’s Community Agreement and in accordance with NZ Biodiversity Strategy i.e. to maintain and restore viable populations of all indigenous species across their natural range and maintainance of their genetic diversity.

With thanks to: Otago Regional Council, Perpetual Guardians Ltd, DOC Community Fund, Otago Community Trust, Backcountry Helicopters, Southern Alps Air and all amazing volunteers.

References:

Aspiring Biodiversity Trust (2018). Rock wren protection and enhancement programme. Helping protect and restore Makarora catchment threatened species.

Heath, S M 1989 The breeding biology of the rock wren, Xenicus gilviventris in the Murchison Mountains,
Fiordland National Park, South Island, New Zealand Otago University

Melville, D S (2013 reprint). Moult in birds. British Trust for Ornithology. Guide 19.

Melville, D S (2011). NZNBBS Bird Banders Manual. DOC, Wellington.

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.

McNab, B K, Weston, KA (2020). The energetics of the New Zealand rockwren (Xenicus gilviventris): could a passerine hibernate? Journal of Experimental Biology 2020.

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.