In and around our back-country waterways, whio are making a comeback. Pat Baskett reports
Good news stories about biodiversity are rare. But here’s one about our rarest and most beautiful duck, the whio or blue duck.
Whio are found in remote areas on rivers that flow swiftly down from the mountains. If you enjoy exploring these places, the chances of spotting a whio squatting on a rock or paddling about close to the river bank have increased remarkably in the last 10 years.
This is thanks to the recovery plan run by the Department of Conservation (DoC) from 2009 to 2019 and to the community groups of volunteers who monitor hundreds of traps to catch the blue duck’s major predator: stoats.
In the central North Island’s Tongariro catchment, Garth Oakden coordinates 800 traps monitored by the members of the Blue Duck Charitable Trust. Traps are spread over 40km, along parts of the Tongariro, Whakapapa and Manganui-o-te-Ao rivers.
He personally checks 20km of traps. When the programme started in 2008, he says, there were 22 birds. A survey done in 2018 counted 186.
“I reckon we’re over the 200 mark now,” he says.
His jubilation is echoed by Nick Singers, a freelance ecologist who runs a similar programme in Turangi. Twelve years ago he could find only three pairs along the Tongariro river and now there are 30.
“It’s just phenomenal,” he says. His goal is to have 50 pairs but he knows they will need “sustained management”. Stoats will always be around.
An achievement to be celebrated
For the huge area we’re talking about, that’s not exactly a large flock but given the nature of the terrain and the odds against their survival, that’s an achievement.
Whio are an endemic remnant of our post-Gondwanaland fauna, an endangered species listed as “nationally vulnerable”. They belong to the limited number of “torrent” species worldwide – ducks whose habitat is fast-flowing rivers – and their closest relative lives in the rivers of the South American Andes.
Here, they live in Kahurangi National Park (at the top of the South Island), in South Westland and Fiordland, as well as in the North Island’s remote high country. Volunteers have recently established a trap line along the Oura river in the Ruahine Forest Park.
DoC describes whio as an icon of back-country waterways and their presence an indication of a river’s health. For Māori they have cultural, spiritual and traditional significance. Māori gave them their name from the whistling sound made only by the males. The female’s call is more like a grunt.
The English name, blue duck, is perhaps a euphemism for the silvery grey plumage which enables them to blend into their rocky surrounds. Their necks and breasts are distinctively speckled orange-brown and their yellow eyes are bright in their darker heads.
Their pale, tapered bill is especially adapted for foraging amongst rocks. A pair of soft black flaps on each mandible protect it from damage and facilitate collecting insects. Whio live on mayflies, stoneflies, caddisflies and freshwater shellfish and crayfish (koura).
Unsurprisingly, they are powerful paddlers, able to negotiate swift currents and eddies. Usually reluctant to fly anything but short distances, pairs remain in the same stretch of river for life – which may be ten years or more.
Nests are made in cavities in river banks or in hollow logs, where the female incubates about six eggs for 30-35 days. The fluffy black and white chicks hatch with remarkable strength. A day later they can plunge into rapids and run along on top of the white water.
“Te whio, noho awa, noho kainga, he mokai nga Ngaitai.” – whakatauki
Whio are relatively unafraid, as this whakatauki (proverb) describes: “Te whio, noho awa, noho kainga, he mokai nga Ngaitai” – the blue duck who lives on the river, who lives in the village, is like a pet for the Ngaitai people.
“You can walk pretty much up to them if you’re quiet,” says Singers.
The specific nature of their habitat – rocky, swift rivers with native forest on both banks – means that no offshore islands can offer sanctuary so their survival depends entirely on successful predator control. Stoats are the major but not sole predators. Most trapping programmes use the trap designed specifically for stoats by DoC, known as the DoC 200, referring to its dimensions. It sits in a box with baffles designed to prevent kiwi from getting in. Its usual bait is an egg.
Stoats take the whio eggs and swim after the chicks but whio are also prey for morepork and native falcon, rats, the harrier hawk, shags and eels. Singers says he saw a trout – those possums of our rivers – take a chick once.
He points out that whio have benefited from the programme to eradicate bovine Tb by getting rid of possums, which involves aerial drops of 1080 in remote areas, and the reduction of other pests. What will happen, he wonders, when Tb is no longer a problem?
In pre-European days New Zealand had a dozen species of duck, seven of which are extinct. Of the remaining five, three – the paradise shelduck, shoveler and grey duck – are targets for hunters in the duck-shooting season, despite being native.
Paradise shelduck or putangitangi, are frequently seen in pairs on open paddocks where they make a distinctive loud alarm call when disturbed. The female is easily identified by her white head. They are described as “partially protected endemic” – hunters can only take a limited number.
Putangitangi were an important traditional food for Māori, who killed them at their moulting sites. But they were relatively scarce in the 19th Century. Later they were able to benefit from the conversion of native forest to pasture and their numbers have increased dramatically.
The shoveler, or kuruwhengi, is also partially protected. Less numerous than the shelduck, it has a large wedge-shaped bill with fine, fibrous lamellae which enable it to sieve soft food from the bottom of lakes and wetlands.
We also have a native duck which so closely resembles the common, introduced mallard that you can be forgiven for not recognising it. The grey duck, or parera, is critically endangered yet still hunted.
Its biggest threat comes from the cross-breeding that occurs from aggressive male mallards. You can identify it by the pale stripes that go from the bill back over its head, and the iridescent green speculum feathers on the wing.
Our smallest, cutest duck is the scaup, or papango, and it keeps whio company on the list of protected birds. They’re also known as black teal – not be confused with the rare brown teal, or pateke. Papango are not numerous but small flocks of their dumpy black shapes are found on lakes in the Rotorua-Taupo area, and in hydroelectric and high country lakes in the South Island. The male only has a bright yellow eye.
You can see whio in an enclosure at Nga Manu Nature Reserve at Waikanae, and Garth Oakden will take you up the Tongariro river to where he knows several whio families live.