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This year was supposed to be a celebratory one for Kākāpō researchers. In February, the Kākāpō Recovery team announced that the critically endangered parrot was set to have its biggest breeding year since 1995. Back then, only 51 of the flightless birds remained alive, spurring New Zealand’s Department of Conservation to launch the species recovery program. 

Today, the program has grown the population to over 140 birds, though it hasn’t been easy.  Kākāpō, the world’s heaviest parrots, aren’t exactly prolific breeders, and have struggled to rebound from their decimation by deforestation and introduced predators. Their reproduction is directly tied to the success of rimu trees, which fruit every 18 months; the parrots in turn breed every two to four years. When the trees have a bumper crop of fruit, researchers typically expect a boom in chicks. This year, unusually warm conditions on Whenua Hou (Codfish Island) and Puke Nui (Anchor Island), the two islands where around 100 birds live and breed, led to a rimu fruit surplus and an early start to the breeding season. 

It seemed a cause for celebration. But for the past three months, the species has weathered a pandemic that threatens the bird’s already precarious population: a fungal virus, called aspergillosis, that killed seven birds and left many more severely ill.

At the start of the season, optimistic researchers took advantage of the rare rimu fruit windfall to try and massively grow the existing population of Kākāpō. After seeing how productive the first round of nests were, workers for New Zealand’s Department of Conservation (DOC), which runs the Kākāpō Recovery project, encouraged some females to breed again. 

“Thirty of the females have nested twice,” says Andrew Digby, chief scientific advisor on Kākāpō for DOC and head of the Kākāpō Recovery team. “We’ve also had more chicks in nests than we usually do. Normally we only have one chick per nest, sometimes two when there’s lots of rimu fruit around. This year, two has been the norm, and some nests have had three chicks as well.”

In all, 86 chicks hatched—more than half the existing adult population, which sat at 142 at the beginning of this year. Although not all are expected to make it to adulthood, the year’s prolific breeding broke every record and was met with excitement from conservationists and observers worldwide.

Then, a bird got sick. “Back in April, we had a chick die of aspergillosis. Then, soon afterwards, we had an adult female die,” Digby says. More and more birds fell ill, and since April five chicks and two adults have died of aspergillosis. 

Aspergillosis is a fungal disease common in the Kākāpō’s environment. It has threatened other native birds in the past, but never the Kākāpō. Digby says only one Kākāpō had ever died from it before this year. Conservationists still don’t know why the disease struck so hard this year, but Digby has two theories.

First, unusual warmth might have led to greater amounts of aspergillus spores in the air. “It could just be that these are normal, healthy birds and that the aspergillus growth is of such a high density that they just can’t deal with it,” he says. Second, there could be an as-yet-undetected virus or disease infecting the Kākāpō that has rendered them more vulnerable to the fungal disease. James Chatterton, who heads up Auckland Zoo’s veterinary services and has been treating some of the birds ill with aspergillosis, says that the zoo is running dozens of tests to search for potential underlying conditions. 

Rachael Shaw, who teaches conservation ecology at Victoria University of Wellington, says that the Kākāpō might have been weakened by the long breeding season—an assessment Digby agrees with. “That’s definitely a real possibility,” he says.

As the scale of the crisis became apparent, Kākāpō Recovery staff leapt into action using the traditional best practice for conservation—adaptive management. Mick Clout, the chair of Kākāpō Recovery and a professor of conservation biology and invasive species management at the University of Auckland, describes adaptive management as a learning-as-you-go process. 

“You make decisions based on evidence,” he says. “You use a technique, you monitor the results, and you alter them as necessary.”

Recognizing that the disease seemed confined to chicks and mothers, the Kākāpō Recovery team began shipping the most threatened birds—those that nested with birds dead from aspergillosis, then ones that had been in contact with them, then the rest of the chicks and mothers—to the mainland for testing. Aspergillosis in Kākāpō is detectable only with a CT scan or endoscopy, and even then, the fungus sometimes escapes notice.

If the birds are cleared, they are returned home. Digby acknowledges that this reintroduces them to a potentially dangerous environment, but he believes the period of threat is over. “We think, if this is an environmental issue, then the conditions have passed in which there would be high aspergillus growth,” he says. Moreover, “none of the affected birds have been males or non-nesting females, and we no longer have any individuals in nests, so we think it’s a much safer environment for them.” 

If the birds have the disease or are likely to have it—currently 13 birds (11 chicks, two adults)—then they are treated in a vet hospital. Auckland Zoo has taken on the bulk of this care, but two other facilities, the Wildbase Recovery Hospital in Palmerston North and Dunedin Wildlife Hospital, are also rehabilitating some birds.

Chatterton of the Auckland Zoo says that the Kākāpō are being treated with oral antifungals and antibiotics. The treatment takes six to eight weeks in most bird species, but can take as long as one or two years in some cases. The most advanced Kākāpō have undergone seven weeks of treatment. 

So far, aspergillosis has been confined to Whenua Hou. The birds on Whenua Hou were stuck there while the outbreak worsened; meanwhile, the breeding population on Puke Nui, as well as backup populations on Little Barrier Island and Chalky Island, have been unaffected by the plague.

The situation is looking better for the birds on Whenua Hou now, thanks in part to the quick, adaptive efforts from Kākāpō Recovery. “As of a few weeks ago, there had been no birds that were tested on Whenua Hou that didn’t have aspergillosis,” Digby says. Early on, the team thought that the entire island population might be contaminated, but since then, 31 birds have been cleared of the disease, 18 of which were from Whenua Hou.

During the height of the pandemic, Kākāpō Recovery didn’t shy away from sharing even the grimmest of details on its Twitter feed, where Kākāpō fans closely follow the exploits of the team and individual birds. “Something that comes out of this crisis is, how do we talk about conservation?” Digby says. “How do we get people interested, make them care about it without just making them depressed?” 

Evidently, the team has managed to strike the right balance. After launching a crowdfunding project to support the effort to save the birds, the team received hundreds of thousands of dollars from people across the world. Those funds will be dedicated to further researching the link between aspergillosis and Kākāpō.

The outpouring of support struck Digby, who recalls how a 9-year-old in the United States asked their friends to donate to the cause in lieu of bringing birthday presents to their party. “Here’s a child who’s probably never going to see a Kākāpō in their life,” he says, “and they care about them enough to give up all their birthday presents.”