Lead has been detected in nesting native kākā chicks in Wellington, but unusually, the birds look to have developed a tolerance to the toxin, a study has found.
Kākā are a noisy, smart parrot, with bright green plumage and blood red patches under their wings and chest. They are particularly animated at dawn and dusk, and some Wellingtonians are known to curse their raucous squawking, while others delight in their cheekiness.
Bird populations have boomed in New Zealand’s capital, thanks to its urban eco-sanctuary, Zealandia. Kākā numbers alone increased by 250% in just 10 years, according to a 2021 Wellington council report.
But the urban environment carries risks – such as paint containing lead – and researchers are starting to take more notice of the presence of lead within avian populations as birds repopulate cities.
Human activity encroaching into the natural world also causes lead problems for wildlife – the most well-known example being the lead poisoning of Californian condors, when hunters leave ammunition in the entrails of carcasses.
Researchers at Massey University sampled 139 kākā chicks at Zealandia over two seasons between 2015 and 2017 for the presence of lead in their blood. The findings are to be published in the next edition of the Science of the Total Environment journal.
The study detected lead in more than a third of the chicks, and concluded that the toxin had either been passed down through food via the parent, or that the chicks had absorbed it through their eggshells, where it was also detected.
“Lead is such an insidious toxin and it has the potential for long-term effects,” said Aditi Sriram, a wildlife veterinarian and corresponding author on the paper. “It can be detrimental to their development, so finding lead in a third of these chicks is significant.”
One of Sriram’s earlier studies found that adult kākā were most likely being exposed to lead from the lead-painted roofs of Wellington’s houses. Now those adults were inadvertently passing the toxin on to their chicks.
Detecting lead in the eggshell was particularly concerning, Sriram said. “Exposure to lead during really critical periods of neuro-development … can actually result in long term cognitive and neurological deficits.”
Most of the chicks with lead in their systems had “lower levels” of lead exposure. Some chicks had “high levels”, but Sriram used those terms loosely because there are not yet established parameters on what is considered a high level of exposure for birds.
Despite this, the young kākā managed to fledge and there was 100% survival rate.
“We did a set of neurological tests and a few physiological tests … and we didn’t find any abnormalities,” Sriram said. “Even the two chicks with what we would consider high levels of exposure – if you had brought a bird to me in a clinic with that level of lead exposure, we would be treating it for a significant concentration of lead – even they survived.”
That has led the researchers to believe that – at least in the short term – the chicks, or species, had built up an innate tolerance to lead.
Further studies are needed to determine if lead causes harm to kākā in the long term, but until then, Sriram is encouraging Wellingtonians to be responsible caretakers.
“Kākā are very intelligent birds and very opportunistic, so they do tend to forage in the urban environment,” she said. “[The community] should be conscientious about not offering them food in their back yard … to avoid them congregating, which is a risk … in terms of their exposure to urban toxins.”