Braided river bird surveys and the challanges of nature

The fourth annual braided river bird walkover survey was a touch more challanging this year due to unsettled weather conditions with strong winds, sandstorms, downpoors and subsequent rising river and lake levels. This highlights the necessary considerations involved such as timing and weather monitoring before undertaking this important work.

A gusty second day on the river with water levels rising after a night of rain. Image Karthic

The Aspiring Biodiversity Trust team were determined to complete the length of the river walkover from Boiler Flat down to the river delta and with the additional help of a new volunteer Karthic (to the left below), a wildlife and conservation film maker with Natural History New Zealand (NHNZ) from Dunedin. Karthic found the experience “quite an eye opener” and savoured the remoteness of the location throughout his stay. He hopes to return when conditions are more suitable for wildlife filming!

Walkover sections being divided up to help maximise cover of braided river bird habitat by surveyors

The ABT bird surveyors in action (above) planning survey route sections and safe river crossings. All key braided river bird bird species were present however in generally lower numbers with more dispersed distribution in comparison to previous years. Total counts will be analysed and compared with national trends for key braided river bird species. This was the first wrybill pair of the year recorded foraging along the waters edge.

Female wrybill with a more slendar neck collar
Male wrybill with a wider neck collar and black patch to the forehead

The male and the female are very similar, with subtle differences in colouration and markings. Nick Beckwith a regular ABT volunteer captured this pair nicely on the first survey day.

A nest site was later found (below) the pale grey eggs and nest site highlight the incredible cryptic adaptations of these species enabling them to breed in such a harsh environment with considerable threats.

The female had briefly left this nest site (below) to forage on aquatic invertebrates along the nearby waters edge which enabled this image.

A wrybill nest site on the Makarora River

Thanks to Wilkin River Jets who facilitated the lower Makarora River section of the survey and the upper Wilkin River section. Image below shows the view up the Wilkin Valley from the jet boat, with snow capped Mt Aeolus in the background. There was certainly a crisp chill in the wind that day despite the blue, blue sky.

The team were fortunate to be able to stay at Makarora during the surveys especially during the busy production of a new top secret film (due out in March 2021).

As the day came to an end for the wonder that is Makarora, the stars appeared and the familar call of a pair of morepork/ ruru could be heard from the forest alongside the soothing flow of the river. Morepork presence is a positive indication of ecosystem health and this species appearers to be increasing in the valley.

The night sky – looking west over the Makarora River towards the Young Valley. Image Nick Beckwith.

*Thanks to all involved and those who helped enable this work. Including Sarah Forder, Nick Beckwith, Karthic SS, Danyel and Alex at Wilkin River Jets, Mt Albert Station and Dan and Carol Orbell.

Funding support provided by (LINZ) Land Information New Zealand.

 

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 🙂

Makarora Braided River Bird Restoration

wrybillchickjpg
Wrybill chick Dec 2017

The implementation of ABT’s Makarora Braided River Bird Invasive Predator Control Strategy commenced this weekend (7-8 April). A team of amazing volunteers helped deploy a number of invasive mammal traps along 15 km of the Makarora River. Trap locations and deployment was informed by previous braided river bird monitoring undertaken during the 2017/2018 survey season and existing information on the movement of invasive mammalian predators (capable of decimating indigenous bird life) such as stoat, rat and hedgehog.

Makarora shallow river crossing – linking arm technique

Volunteers keen to help indigenous wildlife included local Makarora residents, members of Makarora School and nearby residents of Lake Hawea.

Sunday with a little rain and wind…
Makarora river ABT
The beginning of the weekend at Wharf Creek, Makarora River

The day began with loading up of traps on two boats, one a jet boat with an experienced captain Rod Elliott and partner Jos Mclean. Following a jet boat ride to the far side of the river, volunteers were loaded up with traps for particular designated areas and equipped with a GPS. Traps were then securely staked, marked with coloured triangles and numbered to aid future maintenance.

Makarora River
Makarora delta adjoining Lake Wanaka
Makarora School pupil marking invasive mammal trap numbers

Following a trap setting demonstration and health and safety talk, traps were baited and sett according to recognised best practice.

The installation and maintenance of the Makarora braided river trapping network aims to help control invasive mammalian predator numbers so that endangered braided river birds such as wrybill, black-fronted tern, banded dotterel and black-billed gull can nest and successfully raise their chicks without being predated. In the longer term a noticeable increase in braided river bird restoration is desired.

Further traps are to be deployed and monthly trap maintenance will be ongoing during the non-breeding season with more frequent checks during the bird nesting season (spring/summer). Volunteers welcome!

Acknowledgements

Thanks go to all our volunteers. ORC. Also, BRaid for DoC 200 trap supply and production, bait donations from Hawea Flat egg suppliers, discounted radios from Hunting and Fishing Central Otago, waratahs from DoC Wanaka and support from Wilkin River Jets and  Mt Albert Station.

Captain Rod, Makarora River