The Powerful Owl is vulnerable – and becoming more so from baits. But citizen scientists are working to save the species

Two passionate citizen scientists were searching for hope in the fading light, amongst the towering eucalypts and lush tree-ferns in the Dandenong Ranges, east of Melbourne.

It was 7.30pm and Jason Groves and Clare Worsnop were searching for clues, hoping to catch a glimpse of Charlie the young Powerful Owl. Charlie was released back into the forest seven weeks earlier, after being found in a puddle by the side of the road in bad shape, suspected to be suffering from rodenticide poisoning.

They needed to know if, against the odds, Charlie had survived this long after being released back into the forest.

With their bright yellow eyes and majestic woo-hoo call, it’s no wonder these giant owls capture hearts and imaginations across the country.

Unfortunately, these impressive birds are a threatened species, listed as vulnerable in Victoria under the Victorian Flora and Fauna Guarantee Act 1988. They are Australia’s largest owl and can be found along the east coast of Australia, from Queensland through to Victoria. Although Powerful Owls can be found across most of Victoria in forested areas, their populations have diminished and become fragmented due to the significant amount of land clearing that has happened since European settlement. Not only do these owls need forests to hunt for possums, their preferred prey, they also need a tree with a large hollow to nest in, which can take 150-200 years to form. Throw rodenticide poisoning into the mix and these owls could be in real trouble.

After being found at death’s door and rescued from the side of the road by qualified wildlife carers Nalini Scarfe and Michael Goodfellow, Charlie was taken to the Australian Wildlife Health Centre at Healesville Sanctuary. Australian Wildlife Health Centre Veterinarian Dr Phillipa Mason explained that he was anaemic due to blood loss. They examined Charlie and found no injuries, concluding the most likely cause of blood loss was due to the blood not clotting properly because of rodenticide poisoning. To treat Charlie for rodenticide poisoning, Mason described a two-pronged attack, where they needed to administer Vitamin K, an antidote to the poison, and also administer nutrition, to give him the energy required to create more red blood cells.

“It was a real balance because we have a youngster that we need to get back out with its parents so it can learn to be a Powerful Owl, but we also have a bird that we know needs the antidote.”

“We had to balance treating it for long enough, with getting it out while it was still young enough to go back to its parents.”

“We have a youngster that we need to get back out with its parents so it can learn to be a Powerful Owl, but we also have a bird that we know needs the antidote.”

Dr Phillipa Mason

Back in the forest, Groves diligently continued to monitor Charlie’s family whilst he was in care, to make sure they were still in the area and still had their other chick. Groves says “I think having the sibling there was a major factor in a successful release after four weeks, keeping the adults in the core territory and keeping them in parent mode.”

Associate Professor John White, from the Deakin University Powerful Owl Research Team, explains that “returning anything back to the wild is fraught with difficulties – having four or five weeks between when the bird was collected and released is problematic”.

White told me that because of the length of time that Charlie had been away from his parents, the team were worried about how the parents would react when he was released back into the forest.

“We all traipsed out, and on dusk we sat there and we could see the other chick and we could hear one of the adults calling,” White recounts.

He describes how once Charlie was released, his sibling and one of his parents were showing interest, however, there was a scuffle between Charlie and the parent and Charlie disappeared. It looked as though the parent had attacked Charlie. The team were devastated, it seemed as though the parents were not going to accept Charlie back into the territory. Groves tells me “I thought he was gone.”

“I thought he was gone.”

Jason Groves

Thankfully, with their impressive owl detecting skills, Groves and Nick Carter, a PhD student with the Deakin University Powerful Owl Research Team, were able to confirm within a few days after the initial scuffle, that Charlie was back with his parents and sibling. Groves couldn’t contain his excitement. Before even leaving he forest, he immediately contacted the rest of the team to tell them the good news.

“There was lots of happy people then.”

Worsnop says “it looked like a disaster, then it wasn’t, then it was a delight.

“To say that Jason was over the moon would be an understatement.”

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Read more: Finding the powerful owl

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I went out with Groves and Worsnop to search for Charlie, seven weeks after the release, to determine if he had truly been accepted back into the family. Looking for Powerful Owls is a challenging endeavour that Groves and Worsnop spend 15-20 hours a week doing. On the night I went out with them, we spent two and a half hours searching for signs and straining to hear a call that would lead us in the right direction, all whilst attempting to avoiding leeches and logs hidden in the dense ground ferns, waiting to trip us up. I wanted to know why they volunteer so much of their time on this difficult task.

For Groves, it’s a puzzle. It’s about learning all that he can about the owls and sharing that knowledge with researchers and land managers to help protect the species.

“It’s not work. For me, it’s an escape.”

Jason Groves

“It’s not work. For me, it’s an escape. I have a creative mind and I need to keep myself challenged.

“If we’re able to protect the roosts, the nest trees and use all that information, that’s great.”

For Worsnop, it’s about the beauty of the birds, the magical moments she spends with them and sharing her knowledge and passion with others.

“I first found the owls when I first moved to Mount Evelyn… it was very easy to fall in love at that point.

“It’s a magic world that most people don’t even think about. It’s nice to share that knowledge.

“There is nothing more magical than to stand under a tree and look up and see this giant bird looking down at you with these big golden eyes.”

Worsnop is passionate about teaching others about Powerful Owls in order to protect them.

“If they never see it, never hear it, never know anything about it, then you’ve got no hope of protecting it, because they won’t know it’s there and they won’t care.”

Just when we thought we wouldn’t be able to find the owl family, we heard the distant high-pitched trilling of a young Powerful Owl. By this point it was dark, so by torchlight we carefully made our way back down the track and along the road, following the call. We found Charlie and his sibling at 10pm, insistently trilling and flying through the canopy, appearing strong and healthy seven weeks after being released. Groves and Worsnop were delighted, Charlie had truly been accepted back by his family and was thriving.

Charlie was one of the lucky ones, found in time, cared for by veterinarians, released back into the forest and monitored by dedicated citizen scientists. Groves, Mason, White and Worsnop are concerned, however, that many other Powerful Owls are succumbing to the effects of rodenticide poisoning.

What is rodenticide poisoning?

Anticoagulant rodenticides are a class of poisons covering a range of products used to kill rats and mice, by preventing blood clotting, leading to internal or external bleeding and death. There are two types of anticoagulant rodenticides, first generation and second generation.

First generation anticoagulant rodenticides need to be consumed by the rat or mouse multiple times to add up to a lethal dose. Second generation anticoagulant rodenticides however, only require a single dose to poison the rat or mouse and are slower to break down in the rodent’s system, which means they are more likely to lead to secondary poisoning when a non-target animal, such as an owl, eats the poisoned rat or mouse.

The Australian Pesticides and Veterinary Medicines Authority, the body responsible for regulating agricultural and veterinary chemical products in Australia, recently began a review of both first and second generation anticoagulant rodenticides, to reassess the risks associated with their use. This review, however, may take some time, with the statutory period for completing the review being 26 months.

Studies have shown that secondary poisoning by anticoagulant rodenticide impacts a range of species, including Southern Boobook Owls and Powerful Owls.

In a study on Southern Boobook Owls in Western Australia, anticoagulant rodenticide was found in over 70% of owls, with half of the owls showing potentially dangerous levels. This study found that levels of anticoagulant rodenticide in birds increased with proximity to developed areas. A study on the impacts of rodenticide poisoning on Powerful Owls found anticoagulant rodenticides in 83% of owls. In this study, Brodifacoum, a second generation anticoagulant rodenticide, was detected in every owl that had rodenticide in its system. When I asked White about this research, he said the team were surprised and “deeply concerned” by the results.

“It would not have surprised me if we got no Powerful Owls with rat poison in them.”

Associate Professor John White

“It would not have surprised me if we got no Powerful Owls with rat poison in them, because they don’t eat rats and mice particularly often… not at a level that would be driving large numbers of owls suddenly having poison in them.”

White tells me that in areas of Melbourne that have high tree cover, such as the Dandenong Ranges, Mornington Peninsula and Warrandyte, the species is “doing okay at the moment”. He is concerned, however, about the impacts of ongoing tree clearing and rodenticide poisoning on the species in these peri-urban landscapes.

Using the evidence from these and other studies, the Flora and Fauna Guarantee – Scientific Advisory Committee have considered the issue of poisoning of native wildlife by anticoagulant rodenticides and in September 2022 recommended that it be listed as a “potentially threatening process” under the Victorian Flora and Fauna Guarantee Act 1988.

White is troubled, wondering how rodenticide is making its way into the owls.

“There’s probably a lot of owls that have succumbed, unobserved, and died because of the impacts of rat poison.

“We’d be very hesitant to say people are deliberately trying to poison possums, but a lot of poison is making it through the food web.”

The Deakin University Powerful Owl Research Team are doing further research into the issue of rodenticide poisoning in Powerful Owls, but in the meantime, White stresses that action needs to be taken as soon as possible.

“Reducing the amount or even banning the use of rat poisons by the public and limiting it to professionals may well have a positive impact for quite a bit of wildlife.”

“There’s probably a lot of owls that have succumbed, unobserved, and died because of the impacts of rat poison.”

Associate Professor John White

Mason stresses that “the main point that I would like to come out of something like this is that people find alternatives to second generation anticoagulant rodenticides.

“Obviously, rodents are a problem for people in their houses, but there are other ways they can do it, like excluding animals by making their houses less rodent-friendly”

As a scientist and nature lover, White is afraid that if we don’t act soon, these magnificent birds will disappear.

“We’re developing, we’re clearing vegetation, we’re using poisons, we’re doing all of the sorts of things that would suggest to anybody looking from the outside that we don’t care… I don’t think it’s that people don’t care, but I think people don’t know that we’re about to lose this stuff.

“We need to cherish what we have, we need to learn to look after it and protect it while we have it, or it will be gone and we’ll be living in concrete suburbs with artificial grass and very little biodiversity, and that as an ecologist and a nature lover worries the hell out of me.”