Blue duck: the white-water champion
At home in waters which would test a world-class kayaker, the blue duck is an icon of New Zealand wilderness. Yet its future is uncertain. Forest clearance has led to the sullying of much of the bird’s habitat, and now only the remotest rivers echo to its plaintive whio . . . whio.
Clouds of steamy breath in the cold morning air mark the trampers’ progress as they stride along a squelching track. High above them tower ancient podocarps, branches festooned with lesser plants, all clinging and climbing to reach the sky. Recent rain has studded the emerald foliage with diamond droplets, while shafts of sun reveal mossy corners in the goblin maze of the forest floor.
Through the wet ferns the trampers get a glimpse of a churning river. The sound of water fills the forest like the roar from a crowd. Then above the crowd comes a familiar high-pitched whistle, and there, on a boulder, is the source of the call. Neck outstretched, a blue duck shrilly proclaims dominion over his realm of forest and white water.
For those who revel in the outdoors, the blue duck is an icon of the wild back country, where the essence of the land’s ancient past lingers on. If New Zealand could be said to have a literal call of the wild, it would be that of the blue duck, whose wheezy and faintly melancholy whistle—whio—is evocative of bush and tumbling mountain stream, and used by Maori as the bird’s name.
While the call of blue duck can often be heard above the clamour of the rivers they inhabit, their plumage blends well with water and rock. Theirs is not the electric blue of the kingfisher but a hazy slate blue reminiscent of the far-off mountains. They have a greenish tinge to the crown, with rich chestnut speckles on the breast and upper abdomen.
The subtle iridescence in their feathers merges with the hues of their surroundings, and their colour seems to change with the light. Under a sombre sky, when the cloud is clamped down like sheet-metal plate, a motionless blue duck becomes almost invisible among the brooding boulders of the riverbed.
When the first European settlers arrived, blue duck were widespread throughout mainland New Zealand.
Only the offshore islands, including the Chathams and Stewart Island, and possibly coastal parts of Canterbury and Otago were without them. There are no records of blue duck in Northland either, but Maori hunters may have eliminated them from the relatively small areas of suitable habitat there. The name Whiorau Bay (meaning “a multitude of whio”) in the Bay of Islands supports the possibility that blue duck were once present in the region.
Maori traditionally took whio for food, along with other duck species such as the grey duck, parera. Whio were caught either by hand during the moult (when they are flightless) or by using slip nooses dangling from a cord stretched across a stream. The russet breast feathers were used by women as neck ornaments.
European explorers also found blue duck a useful source of protein. In 1888, Quentin Mackinnon led an expedition to find a route to Milford Sound (which would later become the Milford Track). At his base camp, four men and a dog killed large numbers of kakapo, blue duck and pigeons, and made pancakes with blue-duck eggs.
Charlie Douglas, renowned surveyor of South Westland in the late 1800s (see NZ Geographic, Issue 32), wrote, with typical candour, “Its prevailing characteristic is stupidity to an amazing degree. This combined with what appears to be a fatal thirst for admiration is its ruin, and makes it easy prey to dogs and men, and nothing but the inaccessible places it frequents saves it from being exterminated.”
Douglas was one of the first observers who showed concern at the decline of the country’s native birds. During an exploration of the Waiatoto River south of Haast in 1891 he noted, “The ferrets have not got among the birds on this river evidently, as kakapos are squealing about in hundreds. Will have to tie up the dog if I don’t want the camp full of corpses in the morning. But what is up with the blue ducks? When up here before they were in hundreds, now I have only seen one, and he travelled as if Old Nick was after him.”
The decline that Douglas observed has become a rout. The species is absent from large swathes of its former domain, and in regions where it is still to be found populations are small and patchily distributed. Numbers are greatest in forested river catchments in the central and eastern North Island, Nelson, West Coast and Fiordland.
The difficulty of surveying a bird that is largely confined to remote and rugged wilderness areas allows only a crude total population estimate, but it is thought to be between 2000 and 4000 birds.
Although predators and hunting have taken their toll, habitat loss is considered the major reason for the decline of the species. Deforestation has caused the loss of the riparian vegetation that formerly provided cover for nesting and maintained river water quality. Without intact forests and wetlands, the size and destructiveness of floods increased.
Prior to the destruction of much of our native forest, blue duck were common in rivers and streams of gentler grade and at lower altitude than those in which they are now found. Department of Conservation scientist Murray Williams, who has studied blue duck for 20 years, suspects that this quieter territory was “caviar country” for the species. He believes that their present confinement to white water in the headwater catchments of New Zealand’s mountain ranges represents their need for unmodified environments rather than a particular habitat preference.
“Populations of blue duck had drastically shrunk prior to good records being kept,” he comments, “and this makes it difficult to determine what is good or bad habitat for them.” Subfossil remains found far from rivers even suggest that blue duck may once have ventured into forests to feed.
Hydroelectric projects, such as the Tongariro Power Development, have also changed the nature of some rivers. Around Ruapehu, a network of canals and subterranean arteries sucks water from three large blue duck rivers: the Whakapapa, the Tongariro, and the headwaters of the Whanganui. Although the longest Planning Tribunal hearing of its type ever held eventually obliged the Electricity Corporation of New Zealand to maintain water flows above specified minimum levels in the Whakapapa and Whanganui Rivers, the damage was done: one of the North Island’s strongholds of blue duck was compromised.
As our Helicopter thunders over the tussocky spine of the Ruahine Range, ridges scarred with welts of bare earth sprawl beneath us like the limbs of a fallen warrior. Deep, shaded valleys shrouded by a cloak of dark forest fall away to a scrawl of grey stream beds. Ragged beech forest looms to either side as we drop towards a narrow gorge that miraculously opens out to a terrace beside Apias Creek, where we land.
Hidden in dense bush at the edge of the terrace is Rockslide Bivouac, our corrugated iron base for the next few days as a Department of Conservation party I am accompanying searches for blue ducks. It is late spring, and three survey parties are continuing the twice-yearly monitoring of blue duck that was begun in the northern Ruahines by DoC in 1991. My party is led by John Adams, a 20-year veteran of blue duck survey work.
Armed with trout-landing nets—though we are hoping to catch fowl, not fish—we fan out along the river bank. White splashes of droppings atop boulders signal the presence of our quarry. Close inspection of such deposits can reveal to the expert how long since the bird had been there, and what it had recently eaten.
Our search concentrates on log jams, as they are favoured roosting places for the ducks during the day. Despite much awkward grovelling and peering with torches, we find not a single bird. Only when we return at dusk do we see one. The pale beak stands out. As we consider how to catch it, it nonchalantly drops into the stream and floats quickly away—the standard method of escape. Scrambling downstream, we manage to corner the bird, but, with a characteristic bobbing of his head that signals “Plan B,” he promptly flies away.
When they bother to fly, which is not that often, blue duck are swift, with a rapid wing beat, but they stay low and rarely cross land, preferring to follow the snaking river highway. Yet, to the consternation of researchers, blue duck are capable of travelling long distances overland in exceptional circumstances. In 1991, five wild birds from the Manganuioteao River, near Ohakune, were released into the Waiwhakaiho River on Mt Taranaki as an experiment to test the feasibility of reestablishing blue ducks in their former haunts. Within nine months, one pair was found 100 km away, back on virtually the same stretch of river from which they’d been taken. On the basis of this apparent “homing” streak, the scientists decided that transfer of wild birds wasn’t going to be the breakthrough in blue duck recovery that they’d hoped.
Captive-bred birds have been more cooperative. Blue ducks reared at the Mt Bruce National Wildlife Centre in the Wairarapa were released on Mt Taranaki in the summer of 1986-87, and although not all have survived, the discovery of a young unbanded bird indicates they have bred successfully in their new home.
Captive breeding of blue duck, pioneered by the Wildfowl and Wetlands Trust at Slimbridge in the UK, is much more difficult with this species than for other water fowl due to its specialised habits. The main challenge faced by breeders is formulating the right high-protein diet to bring blue duck into breeding condition.
Once the knack of breeding the ducks is perfected, there are high hopes that the offspring will provide a much-needed boost to wild populations. In New Zealand, captive breeding is being pursued by Ducks Unlimited, a voluntary organisation which coordinates a national breeding programme called Project Whio. Throughout the country, 15 registered enthusiasts keep a total of about 35 birds.
Back in the Apias, it’s nearly 10 P.M. before we see any more ducks, and then we spotlight two on the water. With much stumbling about in the bouldery creek bed by torchlight, we manage to catch our first bird. Once it is in the bag, we give chase to a second. It takes to the air and we lose it.
The bird we have caught proves to be a small adult male, weighing 820 grams. Blue duck are smaller than other ducks in New Zealand. In hand, the peculiarities of the bird’s bill are obvious. Rubbery black flaps not seen in any other duck project from either side of the bill and overhang the lower jaw like some sort of duck moustache. These flaps are thought to protect the bony part from damage when the bird is rummaging vigorously for food in stony riverbeds, but they may also be used to scrape insects and algae from rocks.
Aquatic caddisfly, stonefly and mayfly larvae form the major component of a blue duck diet, but the birds will also take blood worms, aquatic snails, midges and small flies. In the South Island they are even known to feed on berries from streamside Coprosma shrubs.
After weighing our bird and checking his leg bands for wear, we release him and trudge back to the bivvy for dinner.
Hail pelting onto the unlined tin roof of the bivvy, and mighty gusts of wind roaring like trains through the forest, punctuate our sleep. By morning, the hail has diminished to persistent drizzle, and the valley is choked with cloud. Adams reluctantly decides that mist netting will be impossible until the wind and rain abate. I can’t help thinking that it’s great weather for ducks, but it turns out that that is not always the case for blue duck.
“During heavy rainstorms, ‘slugs’ of fine gravel are swept into streams like the Apias from rockslides on the surrounding hills,” Adams tells me. “The fine sediment is bad news for the insect larvae that the birds feed on, and it can wreak havoc on blue duck feeding grounds.”
In more stable catchments, where the sediments are coarser, heavy rainfall is not such a problem. Although insects may be washed away in floods, some larvae will survive by seeking shelter in protected parts of the riverbed, wriggling back out when the waters subside.
More serious floods can wash away duck nests situated too close to the river, while on rivers draining the central volcanic plateau the birds sometimes have to cope with lahars. Volcanic mudflows such as those that randomly roar down from the crater lake at the summit of Ruapehu deliver toxins and fine sediment which can ruin habitat for years. After a lahar in 1975, the blue duck population of the Manganuioteao River took 12 years to recover, while the 1995 lahars and ashfall seem to have drastically reduced successful breeding on the Tongariro River.
Blue duck have had plenty of time to adjust to the vicissitudes of the New Zealand landscape. Among the world’s 159 species of waterfowl, most ducks have been around for a mere half-million or million years. However, blue duck have probably been resident here for tens of millions of years. Several blue duck attributes—care of the young, absence of a coloured spot (the speculum) on the wing, similarity between the sexes—suggest to experts that this duck is of ancient lineage, and it has no close relatives anywhere. Only three other species of duck occupy a white-water habitat similar to that used by blue duck, and they are not related to our species.
As a home for blue duck, Apias Creek is well named. Apias is said to be an acronym for “Any Port In A Storm,” after a hunter caught in a ferocious storm on the tops of the range escaped down into the comparative shelter of the stream valley.
By evening, our storm has relented enough to justify another foray outside. Blue duck often hole up in a secluded spot during the day, and are generally most active at dawn and dusk—a habit described by biologists as crepuscular. In parts of the country they’re almost nocturnal, adapting their feeding habits to exploit insects that emerge at night. All the birds we catch on this trip to the Apias are seen after dark, and this night we catch one at last light and two after midnight.
There seems to be a preponderance of male ducks in this river their life history easily, but after some 20 years of painstaking research most of the blanks have been filled in. Adults usually form monogamous pairs, and vigorously defend territories throughout the year. A typical blue duck territory is a one-kilometre-long section of river—a sequence of around half a dozen pools and riffles. The river’s gradient is a significant factor in determining habitat quality, and hence how long the territory may be. If the river bed is too steep it will be unstable, and unable to support a good supply of invertebrates. If the gradient is too gentle, the pools are likely to be deeper and insufficiently oxygenated for organisms to flourish.
Blue ducks defend their territories against their own kind, but are also aggressive towards grey duck and mallard (although they tend to avoid the larger paradise shelduck). Fights against intruding birds can be vigorous, with ducks using their bony metacarpal wing-spurs for striking.
The bonds between a pair typically last several years, and if one of the pair dies, the remaining bird attracts a new partner to the same territory. But pair bonds are sometimes broken. A previously unattached bird, or a neighbouring bird which has lost a mate, may poach a bird from an existing pair.
Most of the poaching entails fighting between males. Alan Reith, a West Coast photographer who regularly spends two months at a stretch alone in the bush photographing blue duck, says he has been amazed by the contrast between the trusting and placid nature of these beautiful birds and the ferocity with which they fight: “They give alarm calls when I set up my umbrella and tripod, but they quickly accept me and are then quite happy for me to get as close as three metres from them. Then the males have these violent confrontations, lunging at each other with outstretched wings, churning the water into froth and occasionally even drawing blood.”
When the resident male in a pair is vanquished in a confrontation with a newcomer, the female will calmly accept the new male as her partner in the territory. The old partner may sulk around the edge of his old territory attempting to mount a comeback (and occasionally he may be successful) or he may disappear entirely, perhaps dying. Alternatively, he may try to muscle in on another male’s territory and partner. Females seem to be in chronically short supply, living on average two years less than the eight years males manage once they have acquired a territory.
How much of this sort of partner-changing goes on? Murray Williams, who made a 10-year study of blue duck in the Manganuioteao River catchment, observed 64 pair-years, and found seven changes due to the death of one of the members of the pair, and nine as a result of male-to-male challenges.
Only birds in pairs with territories attempt to breed, and the first attempt may be at 12 months of age. Breeding may commence as early as July, but usually peaks between August and October, when female feeding increases in intensity and duration as the birds put on condition. A nest site from a previous year may be reused, especially if young were successfully raised there. The nest itself is a shallow scrape or depression in the ground lined with a small amount of grass and a little down, situated under vegetation, among tree roots, in a hollow log or in a hole in the river bank. It is always near the river and well protected, from the sides and from above.
As with many ducks, copulation takes place in the water, and a normal clutch is 4-7 white eggs laid at two-day intervals. Only the female takes part in the 35-day incubation. Her mate usually stands guard nearby. The female leaves the nest briefly to feed with the male in early morning and late afternoon. They call to each another while feeding with soft peeps much of the time. The whio call is the territorial signature note of the male; the female equivalent is a harsh craak craak. Neither of these more vocal calls is used in the feeding context.
On the Manganuioteao Stream, as many as 40 per cent of nesting attempts failed over Williams’ period of study due to flooding or predation (by harriers and black-backed gulls as well as rats, mustelids and cats). Despite the number of eggs laid, on average only one fledgling is produced per pair per annum—and post-fledgling mortality is also high. Some years there is total breeding failure along a stream.
Ducklings have a remarkable ability to withstand strong currents and feed themselves immediately after hatching. Disproportionately large feet assist with swimming, and they can also jump onto rocks, ledges or logs almost as soon as they break out of the egg.
Both parents are active in guarding the young for the usual 70-90 days of development until fledging. The male often trails behind the brood, ever alert for predators and trying to ensure no ducklings are swept away in the current, while the female stays close to her brood, feeding along the river edge.
Clearly, the risk of being swept away is one of the hurdles ducklings have to face in their fast-flowing river environment. Initially, only a small part of the territory is used—a nursery area. For river crossings, a brood bunches together, dad behind, mum in front, and the youngsters literally run across the water.
As ducklings become more adventurous, they feed in swifter water, quickly learning the nuances of their river. Williams has observed that the broods (and adults) make use of microeddies in the current: “They swim with the flow from back eddy to back eddy behind boulders, the parents often staying just upstream to shield their offspring from the brunt of the flow.”
Once the ducklings approach fledging, their parents’ interest in them wanes, and at the same time the adults usually begin their annual moult (January-February). Adults are flightless during this time, and often hide during the day, only emerging to feed at night. It is probably important that the moult is completed and the older birds can fly again by the time that fledglings are actively searching for territories in late summer, because their territories will come under pressure from their offspring.
Later in the 1997 season, Adams and another party of DoC staff return to the Ruahines to put transmitters on to the year’s batch of ducklings. Adams believes that radio tracking from small aircraft will shed light on the fate of newly fledged ducklings and reveal the details of their dispersal from their parents’ territories to their own stretch of river.
However, the breeding season has been dismal, and only a single juvenile is fitted with a transmitter.
In the 1998 season, Adams’ team has more luck. In early 1998, four broods of ducklings are located in the northern Ruahines, and a total of eight chicks receive transmitters. But within only months of hatching, three are dead. One duckling, found injured but still alive, is airlifted out for veterinary treatment, but does not recover from the bites and broken leg inflicted upon it by some unknown predator. The other two die of unknown causes.
But there are high hopes for the surviving five ducklings. The older they get, the greater their chances of survival. Adams plans to follow the fate of these birds with transmitters for another two years. Surviving to duck adolescence is one thing, but the real test of success will be whether they find good territories and eventually breed.
Securing a territory is not easy for young blue ducks. Throughout the late summer and early autumn, fledged juveniles range up and down the river, initially trying to force their way in between established territories. If unsuccessful, they disperse more widely within their birth catchment, or perhaps into a nearby catchment, as one of the ducklings in the Ruahine Range has recently done.
In the South Island, birds have sometimes crossed the Main Divide, but they are generally reluctant dispersers, and movement beyond natal catchments is uncommon. Research to date suggests that juveniles are often unsuccessful at this dispersal stage of their lives, as many are never seen again.
What frustrates researchers is the knowledge that empty suitable catchments do exist—around Mt Taranaki, for example—but the birds just aren’t taking advantage of them. Their reluctance to disperse is a major factor in the long-term survival of blue duck—one that has been exacerbated by the fragmentation of their habitat.
For one last time I plunge into the bone-chilling water of the Apias, gravel scrunching under my boots. It is the fourth day of the ground survey, and it’s time to leave. We have seen just five males and one female blue duck. The weather has packed in again, and there is no chance of getting the helicopter to lift us out. We have to leave the stormy refuge of the blue duck by crossing the Ruahine Range and driving back to Napier.
From the road, the broad farmlands of Hawkes Bay, spreading out to left and right, provide a sobering reminder of just how drastic the loss of habitat has been for blue duck. While place names such as Ongaonga (New Zealand stinging nettle) and Kereru (native pigeon) recall the vegetation and wildlife that once flourished in the district, we see barely a stick of native vegetation amidst the browning paddocks and orchards.
Forest would once have extended right down to the coast and the blue duck’s preference for flight above bush-fringed water would have allowed the young to fly that far. Perhaps they even journeyed along the beaches and up other rivers in their search for new territories. Now after just a few kilometres of forest the hungry young are forced back by farmland.
Perhaps in our rush to convert forested wilderness into something more profitable, we have lost more than we thought. Although the clearance has slowed, for blue duck the losses continue. A helping hand with breeding and dispersal, predator control and restoration of some of their riverine highways is needed to reverse the decline of the white-water champion. Until that happens, the most you are likely to see of them is the picture on the $10 note. When you do, spare a thought for them, and the wild places they symbolise. For if we can’t save a place for the blue duck, what will that mean for the takahe, the kiwi, and the rest of our specialised native fauna.
And what, in the end, will that mean for ourselves?