In 1980, five black robins remained on Earth. One female held two eggs, and the species’ survival depended on them. Don Merton, a New Zealand Wildlife Service officer, took those eggs. He had spent sixteen years trying to save the birds. He could only hope the decision did not seal their fate.

New Zealand evolved in isolation for millions of years without ground predators. Many native birds nested on the ground and had no fear of introduced mammals. When rats and cats arrived, they ate eggs and chicks. Populations declined quietly, without dramatic confrontation, until recovery was no longer possible.

Merton’s involvement with birds began early. At age four, he placed goldfinch eggs under his grandmother’s canary to observe the outcome. The chicks hatched and survived. Twenty years later, he joined the Wildlife Service, one of only two people in the country tasked with preventing bird extinctions.

His first major test came in 1964. Rats had reached Big South Cape Island, near Stewart Island, where three rare endemic species lived. Merton and colleague Brian Bell headed there with nets, a portable cage, and a technique they had refined earlier that year: the world’s first successful inter-island bird translocation.

That technique had been developed on Hen Island, home to the last population of North Island saddlebacks. The task was to move 23 birds to a neighboring island. Using new synthetic mist nets and a portable tape recorder, Merton’s colleague Johnny Kendrick recorded saddleback calls and played them from speakers positioned on both sides of the net. The birds flew toward the sound and became entangled. All 23 birds survived and bred within the year.

The Big South Cape operation was more difficult. Rats were everywhere, consuming nests, eggs, and chicks. The birds, unaccustomed to ground predators, did not recognize rats as a threat. The team divided: half searched for rat-free islands for relocation, the other half caught birds.

August days at the 47th parallel are short, and stormy weather made landings hazardous. The bush wren and New Zealand snipe were caught too slowly. Several captured birds died in cages from stress, as the species had no prior contact with humans. No one knew how to feed them in captivity because there had never been a need to know.

The saddlebacks fared better, possibly because the team already understood their behavior from the Hen Island operation. They caught 36 birds and transferred them to Big Island and Kaimaho Island. The last transport occurred at the end of August, by which time rats had reached the southern part of the island. The bush wren, New Zealand snipe, and greater short-tailed bat disappeared during those weeks. Merton later recalled the saddleback catch as straightforward, but remembered the operation for its failures.

By 1976, the black robin survived only on Little Mangere Island, a small rocky outcrop in the Chatham Islands. Seven birds remained. The forest had degraded, and the team moved the birds to nearby Mangere Island, where more than 100,000 trees had been planted in advance. The descent from Little Mangere involved vertical cliffs. Birds were caught by hand and lowered in cages on ropes.

By 1979, the population had shrunk to five birds. Only one female could lay fertile eggs. She was called Old Blue, for the blue ring on her leg. At nine years old, she was well past the normal robin lifespan of four to six years. The species depended on a single bird that should have died years earlier.

Old Blue initially mated with a male called White, but the eggs proved infertile. She then left him for a younger male, Old Yellow, and only then did the eggs become fertile. The entire recovery program rested on that choice.

Merton had considered cross-fostering, moving robin eggs to other species’ nests, but needed proof that robins would lay again if eggs were removed. After a storm destroyed another pair’s nest, Merton removed the dead egg and the pair rebuilt and laid again. The mechanism was confirmed.

The first foster parents chosen were Chatham Island warblers. The logic was practical: they were abundant on the same island and already raising their own chicks. Robin eggs were placed in their nests. The chicks hatched and grew normally for ten days. On the eleventh day, all were dead. Several team members attempted resuscitation, but none survived.

Later analysis showed that warblers feed their chicks in a particular way up to the tenth day, after which their method cannot sustain a growing robin chick. No one could have known this in advance; no one had attempted it before. The season produced nine birds instead of five because Old Blue laid again and raised chicks herself, but the year had largely been lost.

The following season, Merton chose tomtits, the black robin’s closest relatives. They lived on Southeast Island, fifteen kilometers away by sea. With no helicopter and no regular ferry service, the team built a portable incubator to transport eggs between islands. Each time Old Blue laid her first clutch, the eggs were taken by boat to Southeast Island and placed in tomtit nests. Old Blue would then begin a new clutch, producing three clutches per season instead of one.

The tomtits introduced a new problem. Black robin chicks raised by tomtits absorbed their behavior: foraging methods, social signals, even calls. They did not recognize robins as their own kind and might attempt to mate with tomtits. The team had to return tomtit-raised chicks to a robin environment before the socialization window closed, a period only a few weeks wide. Old Blue’s physical condition also required constant monitoring. Overly aggressive egg extraction could exhaust her, and the loss of the only fertile female would end the program.

By the end of the 1982 season, the population stood at twelve birds, all offspring of one pair. Old Blue continued laying until age thirteen, twice the normal lifespan. In 1984, Merton reported 53 adult birds and 56 new chicks in one season. Old Blue died when the population numbered more than 50 birds.

Parallel to the black robin effort, a separate search was underway for a species that might not exist at all. The kākāpō, the only flightless parrot in the world, nocturnal and weighing up to three kilograms, had been considered extinct before Merton began his career. In 1974, his team went to Fiordland and found a small group of 18 males and no females.

Kākāpō are almost impossible to find without specially trained dogs. They remain motionless during the day, camouflaged among leaves. In 1974, Merton documented their mating ritual: males excavate shallow bowl-shaped depressions and boom through the night at a low frequency audible three kilometers away. The sound resembles someone blowing across the top of an empty bottle, sometimes for eight hours straight. But there were no females.

In 1977, on Stewart Island, the booming sound was heard again. Merton and four two-person teams searched the island and found around 200 kākāpō, again all male. Merton described the moment as despair. The population was larger than expected, but without females, it was effectively dead.

In 1980, a spaniel named Jasper led his handler to a bird in the night forest of Stewart Island. The bird was smaller and slimmer than the males, with a brighter green color. Merton examined the primary flight feathers. In males, the tips carry a spotted pattern; in females, it is absent. This bird had no spots. She was named Mandy, the first confirmed female kākāpō in over a century.

More females were found, then nests and chicks. The species was breeding. Then cats arrived. Cats had been on Stewart Island since the 19th century, introduced by whalers. They hunted at night, the same hours as the kākāpō. Female kākāpō sit motionless on their nests for weeks. The mortality rate from cats in the 1981–1982 season was 56 percent annually. The population that had just been found was disappearing faster than it could reproduce.

Merton decided to move every bird. The operation lasted from 1980 to 1997. Some birds were initially moved to Maud Island, but stoats were found there and several birds died. The program then shifted to Codfish Island and Chalky Island. Every bird was fitted with a radio beacon. Kākāpō today live on four protected islands, numbering about 237.

The methods Merton developed under pressure became standard in conservation biology worldwide. Translocation, cross-fostering, and intensive management of individual animals are now used in programs across five continents.

The question of whether it was irresponsible to take eggs from a species on the brink of extinction is one Merton acknowledged openly. A sick Old Blue, a broken egg in the incubator, a chick dying with the tomtits could have destroyed the species at his own hands. But the alternative was not risk versus safety. The alternative was controlled risk versus guaranteed extinction.

The black robin today numbers around 300 birds with a nearly identical genome, all descended from Old Blue and Old Yellow. This minimal genetic diversity leaves the population vulnerable to future environmental change or new pathogens. Scientists still debate whether this constitutes a true rescue.

Cross-fostering has partial applicability to other species. It worked with the black robin because tomtits are their closest relatives and the behavioral incompatibility was manageable. With more distant species and more complex social behavior, results have been worse. The method is not universal but tailored to specific situations.

Captivity was not a viable option. In the 1960s, five kākāpō were placed in captivity. All five died. Island isolation without predators proved to be the only model that reproduced natural conditions closely enough.

All three rescued species live on isolated islands under permanent protection. One ship carrying rats, one introduced cat, or one new pathogen could repeat the Big South Cape scenario. What happened there in 1964, three extinctions in a matter of weeks, remains a live risk.

On Mangere Island, a memorial plaque bears one name: Old Blue. The forest that Merton’s team planted before the birds were moved has grown. Black robins live in that forest, heard more often than seen. The intensive management program concluded in 1989. From 1990, the population grew without human involvement. The species is now classified as vulnerable rather than critical.

Merton died in April 2011. In his last interview, he said the most important thing was not the method or the numbers, but that they were in time. Kākāpō breed only when certain trees produce a heavy fruiting, which occurs every few years. The next such event depends on the climate, and the climate is changing.