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In December, Richard Cuthbert looked out over a scene of destruction. It was a barely a year after a 7.8-magnitude earthquake had struck New Zealand’s South Island, sending boulders and rocks tumbling down the mountainside. Before, the ground had been soft and pockmarked with burrows for nesting Hutton’s Shearwaters, their chicks hidden down below. Now, most of those nests were buried under hundreds of feet of rubble. As they stood there surveying the damage, an aftershock sent a tremor through the area—more than a year later. Cuthbert glanced at the other biologists nervously.

Cuthbert, the conservation director of the World Land Trust, is considered the world's expert on Hutton's Shearwaters, and was joined by employees of New Zealand's Department of Conservation that day for the first on-the-ground survey of the colonies since the quake. Hemmed in by cliffs and sea, these two remaining natural colonies are accessible only by helicopter. Their high elevation has allowed them to persist despite growing populations of predators—namely, feral pigs, which helped to devour at least eight accessible colonies over a period of 50 years. As a result, the birds are considered endangered by the . It's estimated that around 115,000 pairs nest here.

But that was before the earthquake. After it struck in November 2016, early aerial surveys suggested that up to a quarter of the birds were killed. The four researchers present that day were on a mission to learn how many of the birds had survived the earthquake, and how much of their breeding habitat was still intact. “We knew about 10 to 15 percent [of the area] had been destroyed," Cuthbert says, "but we didn't know what we'd find on the ground in terms of the number of burrows that were collapsed."

The group walked around the site, counting burrows and any birds who showed themselves during daylight hours. As night fell, more birds emerged from their underground homes, proving that there were more survivors than previously thought. Although the numbers are preliminary (the researchers are returning in March to finalize), they estimate that only 20 percent of the colony was crushed by the earthquake-induced landslide.

But any sense of relief was overwhelmed by the sight of the destruction. “It's a place that's so special for me, since I spent a few years living there, and it was quite upsetting to see the damage that had happened,” Cuthbert says. “There was a massive rockfall and a huge land slip that took out about 12 or 13 percent of the bigger colony. It probably killed about 20,000 birds.”

However, the remaining birds “don't seem too concerned,” says Simon Litchwark, a ranger with New Zealand’s Department of Conservation, who was a part of the survey. “There’s still a lot of birds up there. More survived than we thought were going to.”

Litchwark and Cuthbert both noted the tremendous activity of the remaining birds.

“On the ground at night, it was absolutely chock-full of birds,” Cuthbert says. “It was a very busy seabird colony.” 

Despite this blow, the bird’s numbers have been increasing overall due to the sustained efforts of community volunteers, says Ted Howard, a volunteer with the Hutton’s Shearwater Charitable Trust. In the early 2000s, the Trust helped create a third shearwater colony by relocating chicks from the mountaintop colonies to a new site lower in the valley, where it’s growing slowly but surely. The new colony acts as a safeguard in case another earthquake occurs or predators attack one of the two high-elevation sites, and this past year saw the greatest number of birds return, ever. Seventy-two birds made their way back to the site, ready to rear the next generation of shearwaters.

The Trust also protects the colonies from a number of invasive predators. “They’re very smelly,” Howard says to explain why pigs, cats, rats, stoats, and hedgehogs all have it in for the birds. “When pigs get into the colony, they can easily tear through a burrow, and destroy a colony over a few years.” The first two colonies are in such a precarious location that no predators can pose a serious threat; however, the third colony is at a lower elevation, and so requires better protections. Howard estimates that the Trust has spent around $300,000 (around $220,000 in U.S. dollars) on equipment, including a pig pen, which corrals the pigs until they can be killed. (New Zealanders are famously enthusiastic about .)

Howard proudly notes that this year they secured funding for an additional six helicopter rides to go clear out the pig pen and other traps.

“The only way you get amazing mountains like this is earthquake activity," he says. “Earthquakes have to happen. This is part of [Hutton's Shearwaters'] lifecycle. They can repopulate relatively quickly, as long as they're not being picked off by pigs or stoats.”

Correction (01/29/18): An earlier version of this story misstated the number of colonies devoured by pigs. It was at least eight colonies, not around 30 colonies. It also misstated the number of birds that returned to the new breeding colony (72, not 30) and the degree of harm estimated to the colony from the landslide (one-quarter killed, not 80 percent). ̽����ѡ regrets the errors.