In March and April 2025, a cheerful scene has been playing out in Chacabuco Valley in the heart of Chile’s Aysen region. Dozens of baby birds, looking like stripy ducklings on stilts, peck happily in the dirt and grass, investigating their new home. They have been bred under the most careful supervision, and are getting ready for their new life in Patagonia National Park, as part of a reintroduction programme run by the conservation organisation Rewilding Chile.
The chicks are nandus, large flightless birds sometimes known as Darwin’s rhea. In total, there are fifty of them, together with two adults, and they make up the largest reintroduction to the park yet. In doing so, this ambitious project is helping triple the wild population of a once-disappearing bird – and returning a damaged ecosystem to health in the process.
Patagonia National Park: A Landscape in Transformation
Patagonia National Park has been one of Chile’s greatest conservation successes in recent years, and the story of its creation has already become legend in the rewilding community. The park was once a landscape entirely dominated by large-scale sheep ranching. When a combination of overgrazing and the collapse of the global price of wool caused many ranches to falter, the land was bought up by the philanthropist conservationists Doug and Kris Tompkins. Through their foundation, Tompkins Conservation, they sought to restore the natural landscapes of Patagonia to their original state.
Local communities, including former ranchers, were placed at the heart of the rewilding efforts. As the fences came down, the grasslands and forests began to regenerate, and hiking trails were laid out. In 2018, this vast expanse of wilderness was donated to the Chilean state and Patagonia National Park. The success of the rewilding is seen every day by visitors: those staying in the lodge at the heart of the park often find themselves walking to breakfast past wild guanaco grazing in the grounds, while staff swap photos on their phones of local pumas seen in the vicinity.
Some species remain more elusive, Cristián Saucedo, Rewilding Chile’s wildlife director, told Swoop. By the time that sheep ranching ended here, the nandu had almost completely disappeared from the environment. ‘The bird counts and censuses showed a small and isolated population of less than 20 birds due to extensive ranching and fencing, dog harassment, poaching of birds for meat, and collection of eggs putting them at higher risk of extinction.’
The nandu: Darwin’s miniature giant
The nandu is Chile’s largest native bird. They’re closely related to ostriches, and stand around 150cm (five feet) tall on strong three-toed feet, covered in dusty brown and grey feathers. They also play an unlikely role in Charles Darwin’s theory of evolution by natural selection. When the great biologist travelled across Argentinian Patagonia in the 1830s, he quickly became familiar with the greater rhea, which was often hunted by the gauchos he travelled with, but he also heard of a smaller species – the nandu – that seemed to occupy the same ecological niche in what is now Chile. Why should two distinct species live in neighbouring areas with identical habitats, he wondered. And why should they be so similar to the ostrich in Africa?
As Darwin fumbled his way towards the idea that species might share a common ancestor and adapt to their environment incrementally, he went looking for the nandu – only to realise that the gauchos had just served him one up for dinner. By gathering together what had been left over by the cook, Darwin was able to reconstruct a nearly perfect nandu specimen. It’s ironic that although he ended up naming the species for science, he never saw a live nandu e.
Nandus themselves are one of the steppe’s great omnivores. They eat everything from grass and leaves, to seeds, berries and even insects and lizards and the occasional mouse. In doing so, they play a crucial role in dispersing seeds – something that has important consequences for the structure of a habitat and the species within it. Simply put, however much work is put into restoring Patagonia National Park, it can never be truly healthy unless nandu are at the centre of it.
Reintroducing the nandu: A Complex Undertaking
The project to return the nandu to Patagonia National Park began in 2014 with the establishment of the Nandu Breeding Center by Tompkins Conservation and the team that are now part of Rewilding Chile. Every year, chicks are raised and then released into the park in collaboration with Reserve Quimán near Futrono in northern Patagonia. Every two years, artificially incubated eggs are brought from a ranch at Baño Nuevo north of Coyhaique, the only other place in Aysen where wild nandu can still be found.
The process to grow Chacabuco’s nandu population and strengthen their genetic diversity has been slow and meticulous. Each bird is carefully monitored and supported during its transition from captivity to the wild. In doing so, Rewilding Chile has learned enormous amounts about nandu biology and behaviour – including the fact that male nandus are some of the most devoted parents in the bird world.
‘There is a strong bond in parental care that males develop with their young chicks during their first months of life,’ said Saucedo. Understanding that allowed Rewilding Chile to get males to adopt chicks hatched under artificial conditions to increase their chances of survival. To help keep the broods together, the first chick to hatch even whistles for its siblings, which induces a synchronised hatching event.
However much work is put into restoring Patagonia National Park, it can never be truly healthy unless nandu are at the centre of it.
With males keen to adopt, and chicks playing their part by whistling for their brothers and sisters, Rewilding Chile’s field biologists were able to to create blended families of chicks and dads and raise far more nandus than would otherwise survive in the wild. ‘Males are extremely dedicated and fierce if any threat is nearby,’ said Saucedo, pointing to the sky as if to warn of a passing raptor.
Once released, the birds are monitored closely, with weekly direct counts by park wardens as well as camera traps throughout the valley. When adults are released they’re given numbered collars so that individuals can be indentified, but fast-growing juveniles are harder to keep track of, as the collars bring a higher risk of injuries by strangulation.
The project has seen great success. By 2023, Chacabuco’s original population of 20 nandus had reached somewhere between 60 to 70 birds, thanks to the release of over 160 individuals. The effective area of habitat used by the nandu has also expanded, with birds now occupying around 4,000 hectares of the park – a 30% increase on the area where they’re living from previous years. In 2025, there was the largest yet, with 50 chicks and two adult males set free in the park.
The path to a self-sustaining population
While the nandu population in Patagonia National Park is growing, the journey toward a self-sustaining population still has some way to go.
‘Over 20 years it should be possible to achieve a nandu population of more than 100 adult individuals in the wild in the Chacabuco Valley,’ said Saucedo, indicating the number of birds that will be required for a self-supporting population.. ‘Right now, we’re in the middle of that process, trying to accelerate it.’
The most recent results from the nandu census give good grounds for optimism, with wardens recording an increased number of adult males observed with chicks. Males not only care for the chicks, but also build the nests and incubate the eggs, that’s led to an increased focus on releasing males with breeding experience into the wild along with juveniles. To further bolster the park’s numbers, Rewilding Chile has also translocated a group of 15 wild birds from Argentina to Chile in a partnership with their sister organisation Rewilding Argentina.
A symbol for the future
The 50 nandu chicks released this year are symbolic of how an ambitious rewilding project is bringing Patagonia National Park’s ecosystem into balance. Not all will make it into breeding age, but their power is not as individuals or even as a species. Their return is about putting one piece of the jigsaw puzzle back into the picture as just one part of a healthy ecosystem.
Back in Chacabuco, the growing nandu population is back at what it’s doing best: rolling in dust baths, eating the choicest greenery (and the occasional mouse) and happily dispersing seeds throughout the valley. Before too long, they’ll be captured not just by camera traps, but in the lenses of adventure travellers exploring this part of Chile. It’s sad that Darwin never got to see one live and kicking, but with the park wardens and the biologists of Rewilding Chile looking out for them, their future – and the future of Patagonia National Park – looks more assured than it has been in years.
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