Reprise: a New Dawn for Kokako

Phil Bradfield

In 1991, the future of kokako in Mapara Forest rested on just four breeding pairs. Eight years later, after a campaign of intensive pest control including aerial 1080, bait stations, trapping and shooting, there were 49 pairs. In fact, Mapara now has kokako to spare, a donor for re-introduction projects around the North Island. "We had 16 pairs left," recalls Bradfield, biodiversity programme manager at DOC's Maniapoto Area Office. "Which we thought was pretty healthy. But once we figured out how to sex them, we realised we only had four females."

"That's Botswana," whispers Phil Bradfield. "She's one of our oldest breeding birds."

Just a few metres away, the kokako - Bradfield named her in a fit of African wanderlust - and her mate are hopping on long legs from tawa branch to tawa branch, lithe, blue-grey silhouettes in the climbing sun. We took the easy way. Lured them to this leafy clearing with a tape recording of kokako calls. Every now and then, they answer half-heartedly. But the diva won't be performing today; she's content to pick speculatively at the odd berry. Kokako have, with every justification, been proclaimed the world's finest songbird. In typical fashion, the birds ascend the tawa like a spiral staircase, in short hops. She's no sooner reached the crown before Botswana opens her wings and lets herself glide on the still air, over our heads and into the forest beyond, followed by her mate. Botswana is lucky to be here. By 1991, possums, rats, stoats and cats had all but destroyed Mapara's once healthy population of kokako.

"We had 16 pairs left," recalls Bradfield, biodiversity programme manager at DOC's Maniapoto Area Office. "Which we thought was pretty healthy. But once we figured out how to sex them, we realised we only had four females."

Twelve of the forest's kokako pairs were male/male. Social - sexual - order was lost; the situation was desperate. In those days, everybody thought possums just ate leaves and nectar. But the news got much worse one night when a surveillance camera at Mapara filmed a possum forcing a female kokako off the nest and devouring her eggs. It was a revelation, and an escalation.

Since then, says Bradfield, we've learnt that possums will even kill and eat chicks.

"They're very clumsy predators - they're just opportunistic - sort of stumbling upon nests really. Usually the female gets away, but we've had the odd one munched or damaged. And we've had chicks eaten by possums. But they don't eat them like a carnivore; they just nibble a cheek or a leg."

Then there's the indirect impact of possums, which devour fruits and nectar the kokako need to sustain their breeding effort.

Rats have also been caught robbing kokako nests, and every time they're disrupted, says Bradfield, the birds have to start all over again. "They just keep building new nests and laying eggs; perhaps five times in a summer. And they're huge nests - 40cm across - a big investment in time and energy."

We're just lucky, he says, that kokako are fairly long-lived (perhaps as old as 30) and can, when they're left in peace, be prolific breeders. "In a good year, when we're on top of rats and possums, we're getting three eggs in the average clutch.

"If they were poor breeders like kakapo, we'd have lost them off the mainland decades ago."

So began a concerted eight-year campaign against the looters of Mapara. Intensive possum trapping, a network of poisonous baits stations, and traps for stoats, ferrets, weasels and cats. The perimeter fencing was resurrected and the remaining goats hunted down (because kokako browse on foliage at certain times, they also have to compete with goats for food).

But spearheading the offensive was a series of 1080 aerial drops. Four in all, most recently last September.

Bradfield says an aerial operation typically kills well over 90 per cent of possums and rats, and makes a big dent in stoat numbers too, when they feed on what he calls "the living dead" - rats and mice that have eaten a lethal dose of toxin, but are still on their feet.

"Scientists did a study over at Pureora about five years ago, where they attached some radio collars to 12 stoats before an Animal Health Board aerial 1080 drop. We got irrefutable proof that all the stoats died from 1080 poisoning, as we were able to recover the animals and examine the stomach contents."

But some maintain 1080 also kills the very birds it's supposed to be protecting.

Bradfield says a couple of early operations elsewhere using carrot baits did kill some birds, but modern cereal baits and much lower application rates have all but addressed that problem.

Besides, he says, "even if you knocked half the population of birds back, the protection you get for them by knocking the ship rats and possums back, is just fantastic. They build their populations back up immediately".

He says years of bird counts at Mapara back him up. "All birds have increased here. It's generally the larger fruiteating birds and nectar feeders like tui and bellbird that enjoy the really spectacular increases. The insectivores (like robins, tomtits and fantails) don't increase significantly, but they certainly don't disappear."

Meanwhile in nearby Pureora, the scene of four 1080 drops since the mid-80s, recent counts found 3,500 kereru in 1,200 ha, and 800 kaka - the biggest population anywhere.

"Most of our control has been using toxins," says Bradfield, "and no one can tell me 1080 has a detrimental effect on the forest."

Poisons and traps brought Mapara's kokako back from the brink. To the point where 49 pairs now sing for territories. Managers had found they could keep pests at bay, but soon ran up against financial and practical limits.

Not only are aerial and ground operations expensive, but use enough 1080, and animals will eventually become wary of it.

In 1997, DOC turned off all pest control in Mapara. Like throwing a switch.

"We could have carried on ad infinitum," recalls Bradfield, "but there are shyness issues with toxins, so we felt the mature approach was to see just how little pest control we could get away with."

They did nothing for four years. Kokako numbers began to fall, until they were down to 30 pairs. But that didn't faze Bradfield, who says that while breeding success plummets when protection is removed, most forest birds are very long-lived. "So as long as you don't lose the adults, they start pumping chicks out again as soon as you switch the pest control back on."

Nowadays, pest operations are "pulsed" as researchers look for the optimum balance between economy and efficacy. Bangs for bucks.

For the moment, they've settled for two years on, two years off, which Bradfield says should still maintain a good kokako population, and free up limited funds to manage other sites. "So in the long term, you end up with twice as many kokako."

It's a numbers game, played with threatened species. It calls for steady nerves and good data, but Mapara has been a living laboratory for years now. Many pest control and monitoring techniques were pioneered here, and the work will never stop.

But already, Botswana and her mate have been given a second chance, and they're making the best of it. A reprise of the world's most beautiful song.

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