To save scarlet macaws, scientists are rescuing chicks from their lethal parents

Scarlet macaws are an iconic but declining tropical bird. To change the species' fate, scientists are working to counter a lethal parenting method that dooms many chicks to death.

Parker hadn't even opened his eyes when a hand snatched him from his nest.

It was a Monday morning in November 2018 in the Tambopata National Reserve, deep in the Peruvian Amazon, and the featherless chick was frail and underweight, barely longer than a middle finger. He was the youngest of his four scarlet macaw siblings, and that meant he was almost certainly doomed to starve.

Standing at the base of the tree was Gabriela Vigo-Trauco, the Peruvian scientist who orchestrated this abduction.

By studying these birds for over two decades, Vigo-Trauco had discovered that scarlet macaws intentionally starve their youngest chicks. The scientist from Texas A&M University found that almost all third and fourth chicks in multi-egg nests don't make it, and around 25% of second-born chicks meet the same fate.

This brutal parenting approach was once a survival strategy. Now, it is a formidable constraint on recovery for this declining species – with poaching and logging already having driven one sub-species to near extinction across Mexico and Central America.

In 2017, Vigo-Trauco launched a rarely attempted form of rescue-mission, which led her to the chick she named Parker. Her goal was to recruit wild scarlet macaw couples to become foster parents for the doomed chicks. By persuading wild birds to take on the task, she hoped to test out a new lifeline for Peru's neglected offspring – and for the wider species.

Scarlet macaws are impossible to miss. Their crimson plumage stands out against the forest green, and you can hear their screeches long before you see them.

Each female can lay up to four eggs per season, but usually only one or two fly from the nest.

"The parents, particularly the mother, pushed [the youngest] away," says Vigo-Trauco, who is co-director of The Macaw Society, a Peruvian conservation organisation that first revealed this behaviour, after installing nest-cameras in 2007.

"The chick is cold and screaming, and when the father comes, he feeds the mother, the [first and second] chicks, and leaves the third one yelling away."

There was no sibling bullying, and no link to food availability. So why do the parents neglect their younger chicks?

Vigo-Trauco believes parents can't cope well with chicks at different development stages. Even four or five days between hatching can make a huge difference, with the resulting chicks requiring vastly different feeding regimes and even nest temperatures.

The parents are forced to choose, she says. If they stretch too much to feed them all, there's a risk none will make it.

For the relatively healthy scarlet macaw populations of the Peruvian Amazon, the loss of younger chicks is less consequential. But in countries where conservationists fight poachers and loggers for every bird's survival, Vigo-Trauco says that the death of even a handful of chicks is a disaster.

Raising rejected chicks by hand is one potential solution. But it can take between 1.5 to three months for them to fly away. Plus, parrots raised in captivity have notoriously low survival rates: they struggle to feed in the wild, identify predators and form flocks.

So Vigo-Trauco's team turned to the idea of wild foster parents.

After they seized Parker in 2018, Vigo-Trauco's team hand-fed him in their field station for three weeks, following a relentless two-hour schedule.

They also screened the forest's nests to find the chick a suitable foster family, who would teach him how to live as a wild bird.

The technique had been tested by aviculturists raising macaws in captivity in the past few decades, where conditions are controlled and swapping nests means walking across the hall with a chick. It also builds on experiments involving other wild birds, such as yellow-shouldered parrots in Venezuela in the 1990s.

Parker was finally placed in a new nest on 22 December, and his adoptive mother, Tambo, started preening him straight away.

A few months later, he managed to fledge. He was the only fourth chick to do so in decades of observations of wild nests in Tambopata.

The team found similar success with 25 other chicks they've rescued between 2017 and 2019. A further three were successfully adopted but failed to fly the nest (as they were killed by lighting, a predator and disease).

By 2019, Vigo-Trauco was feeling more confident: "I felt like playing chess – moving here and there to see what was possible."

But while some moves forward can be made with wild foster-parenting, it is also beset by challenges.

It is expensive work. In her three-year experiment in Tambopata, Vigo-Trauco had enough funding to pay salaries, lodging and equipment for a 20-person team. Yet such ambition "can't be easily replicated", she says.

It is also hard to pull off.

Rony García-Anleu is director of biological research at the Wildlife Conservation Society in Guatemala. He pioneered the adoption method in the last remaining scarlet macaw populations in Guatemala, and co-authored Vigo-Trauco's paper on fostering.

But the last time García-Anleu's team introduced a bird to a foster nest in Guatemala was in 2019.

Wild fostering requires perfect timing, he says. You need to trek miles into the jungle to locate a nest with a chick in danger. Then quickly find a couple with a suitable nest that is either empty or with one chick of a similar age. 

Instead, his team teach the macaws how to fly, feed and bond in a massive cage, then release them when they're ready.

In 1994 in Costa Rica, macaws had also been decimated by deforestation and poaching. But a team led by conservationist Christopher Vaugh began guarding active nests, introducing education sessions in schools and installing artificial nests to improve the supply of suitable nesting sites.

Their effort stabilised and recovered the population – and demonstrated, according to Vaugh, that one must address the root causes of the species' vulnerability: forest loss and poaching.

Despite its flaws, however, the wild fostering technique is now informing work with other species of parrots, from Argentina to Central America, says Vigo-Trauco.

Plus, since 2020 she has been testing a refinement: skipping the hand-rearing phase altogether and moving chicks from one nest to another as soon as they are born.

This new approach requires more monitoring, but less intensive care for newborns – making it cheaper to run. And, in the project's second year, it has already had success: two nests, each with two chicks with large age gaps, were successfully switched up so the parents could raise two similarly aged chicks.

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Vigo-Trauco believes this may open the door for fostering in places with fewer resources.

"It's nice to see that our relatively healthier population allowed us to become a source of knowledge for others," says Vigo-Trauco.

As for Parker, he managed to leave the nest and spread his wings. Vigo-Trauco's team saw him once again in September of 2019, now a young and confident macaw flying alongside his adoptive parents and his sibling.

"It was 'normal' family," she says, "with two fledglings." 

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