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 tonga.

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 🙂

Updating Whio/ blue duck records for the upper river catchments of the Makarora

One of ABT’s core purpose is the collation and updating of threatened species records within the Makarora Catchment to help facilitate and inform appropriate application of invasive predator control.

ABT have been updating records for whio/ blue duck Hymenolaimus malacorhynchos to help ascertain the current status of this ancient endemic waterfowl species within the upper reaches of the Makarora Catchment. No formal inventory has been completed for this species since the work of the late Peter Child during 1970’s/1980’s.

To date a specialist contractor Paul van Klink and his protected species survey dog (Hoki) has been commissioned to undertake walkover surveys for the upper Wilkin, the Siberia and the Young Valley.

Whio surveyor with protected species survey dog in the North Wilkin Valley

From the results of these walkover surveys and the addition of recent incidental records it is promising to see that there remains a remnant population. Numbers are low and in some cases are limited to just male individuals, a high prevalence of unpaired males on rivers without predator control is often common as nesting females are more vulnerable to mammalian predation. However, evidence of breeding success has been recorded with observations of pair bonds and a fledgling bird.

Adult male whio

This valuable survey work continues to expand for the region with the future aim of restoring viable, sustainable populations of whio/ blue duck within the upper river catchments of the Makarora for future generations.

Down stream of Lake Lucidus, North branch of the Wilkin with Hoki
Whio survey dog in action (Hoki). Image credit P van Klink

Reference

Child P, (1981). Birdlife of Mount Aspiring National Park. Scientific Services No.4. Department of Lands and Survey. Head Office, Wellington, New Zealand.