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Biologist Sofía Zalazar wasn’t born yet the last time a bare-faced curassow was seen in the Iberá forests in Argentina. The bird began disappearing from the wild in the 1970s, surviving only in small populations in forest areas in the provinces of Chaco and Formosa, in the northeast of the country.
A couple of years ago, Zalazar started to investigate the presence of bare-faced curassows (Crax fasciolata) in Iberá National Park as part of her doctoral research. But the information she got from locals was scant and vague. “A big black bird that sings,” elders told her. “The last records are from more than 40 years ago,” park rangers said. She understood then that the bird wasn’t just disappearing from the forests, but also from the collective memory of the community. “We didn’t find anyone who could describe it accurately,” Zalazar said. “It’s been a long time without the species.”
A reminder to help jog that fading memory came in February 2021, with the hatching of three bare-faced curassow chicks. Given the species’ long absence from the region, it had taken two years, since 2019, for the reintroduction strategy to pay off, Salazar said. “Seeing how a species carries out its role in the forests and how it starts reproducing is a very important step in the recovery of an ecosystem,” she said.
The bare-faced curassow chicks were the latest new wildlife births to be recorded in the park as part of reintroduction projects in the past 14 years, all carried out by the Rewilding Argentina foundation. Others include jaguars (Panthera onca), giant anteaters (Myrmecophaga tridactyla), red-and-green macaws (Ara chloropterus) and giant otters (Pteronura brasiliensis).
Tracking the bare-faced curassow
In her doctoral research, Zalazar found that the main causes for the decline of the bare-faced curassow, the largest fruit-eating bird in Argentina, were hunting and loss of habitat due to deforestation.
Resembling a giant chicken, a fully grown curassow can reach more than 80 centimeters (31.5 inches) in height and weigh up to 3 kilograms (6.6 pounds). “That’s why they are wanted for their meat,” Zalazar said.
At the same time, the loss of their habitat to agriculture and ranching cuts them off from sources of water. “The [bare-faced curassow] needs vast territories with forest mass and a good conservation state,” Zalazar said. “This is an inconvenience because it can’t live in any impoverished forest.”
Iberá National Park forms part of a larger reserve alongside Iberá Provincial Park, which together contain 700,000 hectares (1.7 million acres) of subtropical plains. At its heart lie the Iberá Wetlands — a portion of which has been designated a Ramsar Site — that meld into different landscapes like rainforest, plains and pastures. Over the past century, threats to native species like the curassow and the jaguar have led to an ecological imbalance in the region, which scientists from Rewilding Argentina are trying to address.
“An ecosystem isn’t healthy if it doesn’t have all its pieces. It works as an engine that has many parts that make it functional,” Zalazar said. “We want to see Iberá as it was 10 years ago.” For this to happen, though, the species that play key roles in the ecosystem would need to return, including the bare-faced curassow.
Fruits make up 80% of the bird’s diet. And because it’s a big bird, it eats big, fleshy fruits that other smaller birds and mammals can’t eat. This makes it the main seed spreader in Iberá. “By defecating the seeds in different places, it helps to regenerate the forests. At the same time, by breaking other hard and abundant seeds in their stomachs, they control and keep the heterogeneity of the environment,” Zalazar said.
In 2019, the reintroduction project went from paper to action. The plan called of bringing in individual birds from other places. Brazilian-Paraguayan energy company Itaipu Binacional, which operates the Itaipu hydropower plant upstream of Iberá, donated the captive animals that were key for the project.
Talía Zamboni, conservation coordinator for Rewilding Argentina’s Iberá Project, said she remembers the arrival of the nine bare-faced curassows from Itaipu Binacional’s Bela Vista Biological Refuge in Brazil. Before the scientists could move on with the rewilding, they needed to ensure that the newcomers were healthy, so they prepared a space for the birds to quarantine.
“They were isolated and we carried out health checks,” Zamboni said. “We sedated them and took blood samples, which we analyzed in a lab to make sure they weren’t carrying serious diseases.”
During this time, they also fitted the birds with small transmitters to allow for their monitoring later. Then they moved the birds to a cage 14 meters (46 feet) high to acclimatize to their new environment for the next 40 days. Because the birds were born in captivity, they also had to be trained to feed in the wild. “In that time, we offered them native fruits and seeds, which is what they were going to find in the surroundings,” Zamboni said.
The release of the birds didn’t happen right away. They got familiar with their new surroundings progressively. Zamboni said the team opened the cage doors weeks before the final goodbye “so that they could leave and come back when they wanted.” Finally, in February 2020, the nine individuals were released into their new home.
Flying to a new home
The release area the team selected is Yerbalito Natural Reserve, a 1,200-hectare (3,000-acre) protected area in the north of the greater Iberá reserve. The place is considered favorable for bare-faced curassows due to its expanse of forest and link to the Paraná River. “It has a great amount of trees with fruits and forests associated to internal lagoons. It is a very appropriate environment, where [curassows] used to live in the past,” Zamboni said.
The released birds explored their new home during the first few months. The scientists noticed that they traveled across the reserve and to its borders. After that exploration time, there was some good news: they had two breeding pairs. However, their monitoring also showed some unfortunate events.
From this group of nine individuals, four didn’t survive their new life in the wild. They were hunted by wildcats, foxes and weasels. This experience allowed the scientists to design a training method for the prerelease cage, which they’ve since used with a different batch of bare-faced curassows that they plan to release in September.
Zalazar, who is now responsible for the monitoring, said that, “with this second group, we’ve strengthened training. We show them their future predators so that they recognize their presence and can escape in time.”
In spite of the early loss, the project gained momentum with the new breeding couples. Once consolidated, they started to build nests, and one pair completed the 30 days of incubation in November 2020. The Rewilding Argentina team followed the entire process. However, the outcome they had been hoping for was delayed yet again: “When the eggs hatched, the chicks jumped to follow their parents but they were automatically eaten by predators,” Zalazar said.
This was something she’d already seen when monitoring wild curassows in Argentina’s Formosa province. Because the birds only lay two eggs at a time, the challenge was to preventing the next clutch from also being lost. “We learned that we had to take care of the chicks because they are vulnerable,” Zalazar said. The scientists got ready for the next laying, which had a happy ending in February 2021. This time, when the eggs hatched, the chicks and their parents were recaptured and isolated in a prerelease enclosure so that they could survive the most vulnerable period of the young birds’ lives.
Seeing a species grow in an ecosystem from which it had disappeared was an exciting scene for those involved. They expressed high expectations for the release of 10 curassows that arrived from the Criadouro Onça Pintada jaguar reserve in Brazil. “The arrival of these bare-faced curassows highlights that we need to continue working during these pandemic times, specifically for conservation, since these pandemics are the result from the environmental crisis,” said Gustavo Solís from Rewilding Argentina in a recent video.
The second release happened in October 2021, when the curassow’s breeding season started. Zalazar, who takes a long-term view of the project, said she’s hopeful that within a decade, Iberá will be populated by bare-faced curassows again. She said she wants to build self-sufficient populations in other places from where the bird has disappeared or where only a few individuals remain.
A third release of bare-faced curassows, also from the Criadouro Onça Pintada jaguar reserve, took place at the beginning of January 2022.
Bare-faced curassows return to the Gran Chaco
This includes the Chaco region, about 400 kilometers (250 miles) west of Iberá. Zalazar’s research indicates that small groups of bare-faced curassows persist there, but scientists don’t know the exact population of the species in Argentina. The best estimate they can agree on is 2,500 individuals. Given the perilous decline of the bird and its categorization as endangered in Argentina (globally, the species is listed as vulnerable), scientists with Rewilding Argentina say they support local initiatives to boost the population.
On June 5, 2021, they were able to record another small win for the species: the first release of two bare-faced curassow pairs raised in captivity in the Chaco.
Marta Soneira, the Chaco regional secretary for territorial development and environment, described the release as a “historic milestone” in the province’s environmental agenda. Jorge García, director of the Sáenz Peña Ecological Complex, where the birds were raised and trained, added that “it’s an unusual and beautiful event that every time we open a cage, an animal has the chance to live free.”
Rodrigo Fariña, the species coordinator for the educational program of bird conservation group Aves Argentinas, recalls the day as a happy event and highlights the many parties who made the release possible: the Chaco provincial government, the Sáenz Peña Ecological Complex, the National Parks Administration (Conicet), Rewilding Argentina, and Aves Argentinas.
“Different initiatives that had been in the works for years came together. Conicet’s previous research highlighted the need for reintroduction projects to strengthen the reduced populations,” Fariña said.
Along with the conservation projects, the groups are trying to mitigate the impacts of hunting in the area. Because the bare-faced curassow was declared a natural monument in the provinces of Formosa and Chaco, it’s important to talk about the threats the bird is facing. “These rules determine that hunting them is illegal, and promote the species,” Zalazar said.
Park rangers and scientists interact with residents of nearby towns to educate them about the threats the bare-faced curassow faces. “I’m excited because many people in the Chaco region recognize it and want to contribute to its conservation,” Zalazar said.
The Iberá and Chaco forests are once again home to the bare-faced curassow and have recovered a native species. The growth of these populations will be key in the coming years to ensuring the species’ conservation.