Makarora Braided River – an under estimated biodiversity hotspot

Makarora braided river approaching the head of Lake Wanaka. BRaid (2017).

From the headwaters of the Makarora on the eastern flanks of the Southern Alps near the Haast Pass in Mt Aspiring National Park. The Makarora River flows south west and is joined by the Blue and the Young Rivers, then extending its braid plain further meeting its confluence with the Wilkin River before dissipating its energy into the head of Lake Wanaka.

Driving along the Wanaka Haast highway the Makarora braided river habitat is often overlooked or missed totally, yet the Makarora River is quite spectacular and is an important habitat for a number of important endemic New Zealand bird species and an array of other flora and fauna. A section of this captivating landscape can be seen in the video footage https://www.youtube.com/watch?v=g242GDSweiA produced by Braided River Aid (BRaid) on a frosty July morning. Braided rivers (defined by migrating, weaving channels of water between temporary islands of gravel) are iconic habitats unique to New Zealand encompassing an array of wildlife found nowhere else in the world.

There are a number of endemic bird species which depend on this habitat to complete their breeding cycle. During spring, braided river birds such as wrybill, black-fronted tern and black-billed gull can be seen returning to their breeding sites within the South Island.

The wrybill or ngutuparore is the only bird in the world that has a specialised bill which bends to the right, allowing it to feed beneath boulders and along the surface of the water on biofilm. This charismatic grey plover is nationally vulnerable relying on the unique braided river habitat to maintain its life cycle.


Adult wrybill nesting within braided riverbed (OSNZ courtesy of Dianne Parker).

Here the wrybill nests, lays eggs and rears chicks, its cryptic colouration blended effortlessly amongst the alluvial gravels of the riverbed. From January, onward wrybill flocks migrate north to their wintering grounds mainly in the Manakau and the Firth of Thames with smaller flocks elsewhere.

Juvenile wrybill at Miranda chenir shell bank (Firth of Thames) wintering site. Rachel Hufton

The black-fronted tern or tarapirohe, nationally endangered, is an attractive and highly distinctive bird in breeding plumage, slate grey contrasting with a black cap and bright orange bill and legs. Black-fronted terns also breed only on braided riverbeds of the eastern and southern South Island, from Marlborough to the Southland within small colonies and have now returned to Makarora. Their eggs and chicks are also well camouflaged against braided river gravels.


Black-fronted tern roost on a gravel island at Makarora. Rachel Hufton.

The black-billed gull or tarapuka is the most threatened gull species in the world. Though still relatively abundant, numbers of birds throughout the South Island have rapidly declined. The black-billed gull is more slender than the red-billed gull, with a longer bill and nests in colonies mainly on sparsely vegetated gravel riverbeds.


Black-billed gull colony on the Makarora braided river. Rachel Hufton.


Other braided river birds present on the Makarora include banded dotterel and South Island pied oystercatcher. The banded dotterel is the most common small plover of New Zealand coasts, estuaries and riverbeds but is nationally vulnerable. Banded dotterel breed within the braided river habitat but also use other habitats for nesting. Often seen running along the waters edge whilst foraging for invertebrates.

The South Island pied oystercatcher is the most abundant oystercatcher in New Zealand but is declining nationally. Pairs of South Island oystercatchers are often seen breeding in braided river beds but also within adjacent farmland. The conspicuous black and white plumage, distinct call and long red bill make this a familiar species.

Braided rivers are dynamic habitats, and as a result are threatened by a wide range of factors. These include habitat loss due to hydroelectricity development, weed encroachment of braided river breeding habitat, and recreational use of rivers. But the most significant impact is predation by introduced mammals.Black-fronted tern’s, wrybill’s and their nests are preyed on by rats, stoats, ferrets, ferral cats and hedgehogs. In addition, predation by southern black-backed gulls and Australasian swamp harriers, both of which have become more numerous following changes in landuse.

Considerable conservation management efforts have been made on some New Zealand braided river habitats, predominantly in the McKenzie Basin region and Canterbury which have positively contributed to braided river bird populations. This is evident in the Tasman Delta where Kaki black stilt have been reintroduced. A now rare species, once historically found throughout the South Island braided rivers.

The Makarora braided river requires collaborative effort to help restore, maintain and promote these specialised braided river birds to flourish for future generations worldwide. This can in part be achieved through advocacy and awareness raising. A recent braided river biodiversity and conservation workshop delivered at Makarora by a local ecologist, was a great way for students to connect with nature whilst learning about braided rivers.

Students and staff from Makarora located school camp following interactive workshop on braided river biodiversity, conservation and river safety (Andrew Shepherd).

Makarora braided river birds need help to successfully fledge their chicks this year without being subject to invasive mammalian predation from stoats, rats and hedgehogs. Any donations towards invasive mammalian trapping efforts on the Makarora braided river will be gratefully received by the threatened bird species that are beginning to nest. Donations or the sponsoring of traps can be made through the Southern Light website. With thanks.

Wrybill chick (OSNZ courtesy of Craig Mckenzie).

 

References

BRaid (2017) Drone video footage. Makarora and Wilkin River.

Hauer, RF. & Locke, H et al (2016). Gravel bed river floodplains are the ecological nexus of glaciated mountain landscapes. Applied Ecology. Vol 2, No 6.

nzbirdsonline.org.nz

Peat, N. Patrick, B Rebergen, A. (2016). Rivers Rare. The first 25 Years of Project River Recovery (1991 – 2016). Department of Conservation, Wellington, New Zealand.

Wittington, RJ. (2015). The foraging ecology of non-breeding wrybills (Anarhynchus frontalis) in the Firth of Thames: a thesis presented in part fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University, Palmerston North, New Zealand.

 

Further information contact Ecologist: Rachel

 

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