10 Powerful Owls
About this episode
A Powerful Owl can live quietly above a city and still feel completely wild. Scientist Nick Bradsworth shares how to identify Powerful Owls, what they eat, where they live and why hollow-bearing trees matter.
Episode illustration: Powerful Owl
Nick Bradsworth is a PhD Candidate in Urban Ecology at Deakin University. His research has focussed on addressing a major scientific knowledge gap - the movement pathways and habitat available to the Powerful Owl. The Powerful Owl is Australia’s largest owl, with a wingspan of up to 1.4m. Nick is here to share his knowledge about this incredible bird and to how ensure that it can thrive in the wild.
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Kirsty: This episode was recorded on the countries of the Bunurong Boonwurrung people and the Wurundjeri Woiwurrung peoples of the Eastern Kulin Nation. I would like to pay my respect to Elders both past and present, and extend that respect to all Aboriginal and Torres Strait Islander people listening to this podcast.
Kirsty: Welcome to Weekend Bird. I'm your host and fellow bird nerd, Kirsty Costa. Nik Bradsworth has been studying Australia's largest owl, the Powerful Owl, as part of his PhD in Urban Ecology at Deakin University. Nick remembers loving birds from a very young age.
Nick: I can't really remember an exact time when there was a trigger point that made me love birds. I've always loved birds since a very young age. I've always kept chickens at home and mum kept aviary birds as well, was breeding aviary birds at home. So I guess I've always been surrounded by nature and wildlife and. and birds. This interest in birds has taken me through throughout my life. Despite my young age, I've pursued volunteering opportunities with birds through to studying them and now working with them as well.
Kirsty: In the last episode, Dr. Marian Weaving talked about a bird called the Tawny Frogmouth. Despite its appearance, this frogmouth is not actually an owl. It's more closely related to a bird family called the nightjars. In this episode, we're going to learn about the Powerful Owl, which is an owl for realsies and is found from south-eastern Queensland to South Australia.
Nick: They're Australia's largest owl species. They stand at about 65 centimetres head to tail. So very large birds, they're about as large as two footies put together, which is a good size comparison. And when you do see them out in the field, out on the street or in an urban reserve, they really do take your breath away. So they're usually dark brown feathers on the back. They've got a bit of brown and whites on their belly. But the giveaways of the Powerful Owl is the bright yellow beady eyes and then very large talons as well. They're certainly appropriately named. So their call is very deep because they are so large. It's it's like a "woooo wooooo" sort of sound. And there is a very slight variation in the calls between males and females but to the general listener, you wouldn't be able to tell the difference. It does take years of practice. The types of habitat that they prefer are forested environments. There is a bit of a traditional view that Powerful Owls will only occupy forested areas. And they are still found in forests, however, through our research at Deakin University and through other projects through BirdLife Australia in Sydney and Brisbane, we're finding an increasing number of Powerful Owls in utilising urban environments. And so that's what a lot of our research has been about, is understanding why these owls here and what can we do to help them stay here. The Southern Boobook and the Powerful Owl are a part of the same family. They're part of the hawk owl family. And so as I said, they've got those big talons, bright yellow, beady eyes, brown plumage. And the Southern Boobook is much smaller, they're more similar in size to a Tawny Frogmouth. But then the Tawny Frogmouth, on the other hand, typically grey in colour, they've got a really wide beak and dainty little, almost like fingers rather than talent. And so that's developed over time for capturing different a different type of prey. So frogs, mice, insects is what the Tawny Frogmouths will eat. We might also get the Barn Owl, but that's probably more on the on the urban fringe and agricultural environments, we might see Barn Owls.
Kirsty: Powerful Owls eat possums, even those big Brush-tailed Possums. When it comes to their diet, they are what Nick calls a 'generalist'.
Nick: They will not only eat possums, they'll eat whatever is abundant at the time. So there's been studies on this. They've looked at their diet over summer months and they've found more insects, things like cicadas and beetles have come into their diet when there's more insects around. They're supplementing their diet with what is abundant at the time. Even things like Brush-turkeys have appeared in their diet along with koalas and rabbits and birds. But down here in Melbourne there's been lots of research into their diet and in many urban reserves they're pretty much only eating those main two possum species, the Common Ringtail Possum and the Common Brush-tailed Possum, and then supplementing that with some birds and other things as well.
Kirsty: Nick and other scientists have discovered that the Powerful Owl builds its nest over winter, which is a little bit strange because Australian native birds tend to nest during spring and summer.
Nick: They use large oak tree hollows to nest in these hollows can take 100-300 years to develop. The hollows need to be a really large size to hold both the female and possibly up to 2 to 3 fledglings chicks. We're talking a really large hollow size to be able to have the space for those three owls in there. The chicks look completely different to the adults. They're pretty much entirely white, and then they've got sort of like a Zorro mask on their eyes. They've got beautiful grey sort of black Zorro mask over their eyes. They're just amazing. And they are so fluffy when they come out of the hollow. They're just adorable. And they have a very different call as well, which I won't try and mimic - it's we call it a trilling. It almost sounds a bit insect like, but so it's very different to the deep wooos of the adults. The problem with their nesting is that many of the trees that they use to nest in are being taken out of urban environments. Some trees don't even reach the point where they can start developing hollows. I think I read the average life of an urban tree might be about 60 years old, but we've got eucalypts that aren't going to start developing hollows until they're well over 100 years old. That's really important that we're protecting tree cover in urban spaces for these owls. What my research has been focusing on is understanding the spaces that they're using in urban environments. So it's really important that we do this because we need to understand where owls are currently so that we can protect that habitat now and then we can use that understanding to do things like revegetation in other areas to encourage Owls to those areas. The nesting sort of comes a little bit later when we know there's Owls there, but they don't have hollows or they need some help. So it's really understanding what spaces they're using in urban environments. And I've been doing that with the use of GPS transmitters. And so these really amazing tiny little devices that we can attach to these owls and then let them go and we leave them for about a month and month and a half and every single night it's recording where the Owl is. It's just amazing information that we get from these Owls, where they're going to the types of areas that they prefer to be in, but also getting information on areas where we don't personally have access to like private land. And that's so important in urban environments because by the time you get permission to access someone's property to go and take a GPS recording of the Owl, it could be a kilometre away. So these devices, because they automatically record where the Owl is, we program them to record every 20 minutes and they do that throughout the whole night. I'm sleeping at home in bed and the Owls are out there recording information for me. So I've been able to stay a little bit sane through this research.
Kirsty: Right now if you've got time and it's safe to do so, pause this podcast and look up Powerful Owl chick images on the internet. Cutest. Babies. Ever. I'll also share some of Nick's videos on social media. Our handle is @birderpod. Nick's research is focused on addressing a major scientific knowledge gap, the movement, pathways and main habitat available to the Powerful Owl.
Nick: Trees are really important for many aspects of parallel ecology where they sleep during the daytime, so that's called their roosting spots. Tree cover is really important for their movements. They'll pretty much only move in areas where there is tree cover. That's been part of the research that we've found is that when owls come up to an area, say, that has really high residential areas, they'll either not go into those areas or they'll move over them really quickly to connect to the next patch of habitat. That might be an urban reserve that is isolated in this sort of urban matrix that is mostly residential and industrial areas. So that's been really interesting and important information to find. And then the river systems are really important as well. River systems are often areas where there has been reduced development over time because of the flooding risk to residential areas and so trees have been left there. Quite often in Riparian areas (river systems), we have tree cover that is quite mature and we call that 'remnant trees'. They are really, really old. River systems have been important as Powerful Owls are pretty much always just moving along areas of river systems through urban environments because that's where the habitat is and that's the safe areas where they can move through. Combining all of this information, we can look at how much space they're actually using. What we've found out is almost 400 hectares. I did some maths that was about 200 MCG ovals put together and that's just for one Powerful Owl, like a pair would share that space, and we'd probably expect the males to have a slightly larger home range. But, but that's the average, about 400 hectares per Owl. And that does vary and it depends on the type of habitat that the Owl has set up home in. If it's an area that has everything that they need, they're more likely to have a smaller home range if they've got somewhere to nest, something to eat, somewhere to rest. During the daytime, we'll see these smaller home ranges. But then as we get to more agricultural environments and really highly urban environments, we're starting to see larger home ranges because they're having to connect different patches of habitat. That's been really interesting seeing these sorts of variation in range sizes. There's only been a couple of other studies that have been successful in catching Owls, so we've been really lucky to be able to document so many in Melbourne. But some of the other studies have found range sizes up to about 3000 hectares and they've been in environments where the habitat just hasn't been as good as some other forested areas.
Kirsty: 200 MCGs or 400 hectares means that hundreds, or even thousands, of properties where everyone needs to be thinking about how they can support wildlife like the Powerful Owl. It's not just a tree or some random plants. It's neighbors and communities coming together to think about the design and improvement of urban spaces. This is a huge challenge and Nick and his team are trying to tackle it.
Nick: We work very closely with local land managers. So Parks Victoria, we've got really good relationships with many of the councils around Melbourne as well. We provide our findings to councils that are interested so that they can protect the spaces that Powerful Owls are using. And it's been really great having these collaborative relationships with people that are actually on the ground doing this work so that we can ensure that power flows persist in urban environments into the future. But then, on a more global scale, a lot of my research has been highlighting the importance of apex predators. The Powerful Owl is an example of an apex predator. If you think of a food chain, they sort of they sit at the top of the food chain and generally nothing will eat a Powerful Owl or an apex predator. But they have really important roles in contributing to biodiverse ecosystems through their hunting patterns and eating more abundant prey items. that's sort of the bigger picture of of what I've been doing and highlight the importance of having predators in urban spaces.
Kirsty: Powerful Owls are on my birding bucket list. Everyone seems to spot them, but for some reason I miss them when I'm out birdwatching. Thankfully, Nick is here to help with a list of three things to look out for.
Nick: When you're out going for a bushwalk, say you can look for what we call whitewash, which is their poo and it's a very pasty white poo. And when you find a Powerful Owl roost, it is very concentrated as in it's in a small space, maybe 1-2 metres squared, depending on how high they're roosting in the tree. So you can look for that. You can also look for pellets, which are parts of their diet that they can't digest. So that's things like feathers, fur bones and exoskeletons of insects. They cough these pellets up or vomit them really in this pellet form. And for a Powerful Owl, they can be probably 5-10 centimetres long. Then the other thing that you can look for are their feathers. It can be a bit hard to describe what what a Powerful Owl feather looks like. But generally what I'm looking for is a feather that has distinct sort of light brown and white, barring across the whole feather itself. If there's some sort of mottled colour in amongst the white, it's probably something else, such as a Tawny Frogmouth. So there are three things you can look for.
Kirsty: Here is Nicks advice on how we, as wild bird watchers and wild bird admirers, can help protect a species like the Powerful Owl.
Nick: A lot of us are living in urban environments now because of the opportunities that they present to us. But we need to be giving back to spaces like the Powerful Owl and other urban spaces as well. So probably the number one thing that you can be doing is retaining any tree cover that you have in your backyard. If you're worried about a tree, you should get advice from an arborist about what you can do to still have the tree there, but maybe support limbs of that tree so that these trees are retained in the landscape. The second thing that I recommend is supporting that tree cover by planting trees, going to your funding, your local indigenous nursery and planting some tube stock trees. These are really cheap, like maybe less than $2 for a little tube stock and you can fill out an area really quickly and support maybe not nesting in in the immediate term, but definitely within ten years you could have some acacias, some wattles, grow up and support the roosting requirements for Powerful Owls in your backyard. they're probably the two most important things. You can always report sightings to BirdLife Australia as well, which is another way that you can get involved. If you go to the BirdLife Australia website, they've got an email there for the Powerful Owl project and they will submit the records to BirdData, which is managed by BirdLife Australia. That sort of information becomes really important to people like myself, researchers at universities, so that we can use information gathered by citizen scientists to do all sorts of interesting things from modelling through to seeing where Powerful Owls are and where they aren't, so that we can make more informed decisions about how our management of urban areas.
Kirsty: A link to BirdLife Australia's Powerful Owl Oroject is in the episode notes and also on our website weekendbirder.com. You'll also find a link to Nick's awesome Powerful Owl photos and research. Sometimes news about the state of the environment can leave me feeling pretty down, but Nick has just reminded us about how amazing nature is and how people around the world are working together to care for birds and their habitats. Happy birdwatching.
