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Two adult Powerful Owls feeding portions of a Grey-headed Flying-fox kill to two juveniles. Photo, P. and A. Hayler.
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... Zoologist volume 38 (1) suspended for approximately 40 sec, looking around and pecking at the prey intermittently. As the owl ascended to its original perch, the prey's wings were seen drooping limply, indicating that it was dead at this time. The owl led the juveniles to an exposed branch where it fed them (Fig. 3). Still photographs of the feeding confirmed the identity of the prey as a flying-fox. (Fig. 4), which did not struggle after it was struck, indicating that it probably died instantly. The owl flew from branch to branch with the juveniles following until it settled on a perch and commenced feeding the ...
Citations
... Another trophic link would be fly eggs on bat pellets (Helen Smith, pers. comm.) and a potential link is the Powerful Owl Ninox strenua, which preys on Grey-headed Flying Foxes (Mo et al., 2016 ). Our report on food links related to this bat and its cicada prey opens a new perspective in the megabats-insects trophic relationship. ...
Cicada mass emergence offers a plentiful and energy-rich food source for a variety of predators, mainly birds and spiders. Megabats (Pteropodidae) mostly feed on nectar and fruits, but occasionally prey on insects such as sap-sucking cicadas and fruit-eating beetles. We observed and documented with photographs the behavioural repertoire of the Grey-headed Flying Fox Pteropus poliocephalus while hunting and consuming the Black Prince cicada Psaltoda plaga in Sydney, New South Wales, Australia. The bats used three main tactics while hunting the cicadas: a) flushing and/or catching cicadas on tree foliage while clambering over branches or landing on the foliage, b) lunging from a perch after spotting a resting cicada, and c) pursuing cicadas on the wing. Upon securing a cicada the bats flew off and landed on a feeding perch, where they chewed the prey and spat the remains as a pellet below this perch. On the ground, the pellets were usually sought by large ants that tore off pieces from these remains, the ants transporting them to the nest. Small ants aggregated on the pellets probably to seek the remaining sap, after which they left the pellets. The above described events showed three main food links: a) cicadas feeding on plant sap, b) bats preying on cicadas and spitting the remains as pellets, and c) ants feeding on bat pellets. The links illustrate a food chain that include plants, cicadas, bats, and ants. Additional food links we observed were: 1) cicadas feeding on different plants, 2) cicadas preyed on by diurnal animals, 3) dead cicadas consumed by ants, 4) dead bats consumed by birds, and 5) nocturnal raptorial bird that may prey on bats. This report seems the first to mention food links within a megabat-insect trophic interaction.
... Their foraging behavior is unlike that of the similar-sized, North American great horned owl (Bubo virginianus) which hunts mostly ground prey (Johnsgard, 2002;Olsen et al. 2011). Instead, the powerful owl will usually undertake the still-hunting search method by perching high (sometimes on dead tree branches) which provide suitable vantage points to listen and wait for potential arboreal prey (Mo et al. 2016). If a prey item becomes available, they will fly from their perch, and manoeuvre through the dense canopy vegetation to ambush the prey (Olsen et al. 2011). ...
... This suggests that powerful owls prefer to hunt earlier in the night in riparian vegetation, because riparian areas are resource-rich environments (Gregory et al. 1991;Palmer and Bennet, 2006), and therefore likely to contain elevated prey densities. Early hunting attempts during the twilight and dusk hours have been documented by Mo et al. (2016) in southern Sydney. Powerful owls are capable of carrying prey heavier than their own weight (i.e. ...
Examining the movement of apex predators is difficult in urban environments due to private land ownership; however, understanding their movement is critical given the current and rapidly increasing rate of urbanization globally. Of equal importance is the understanding of what landscape factors allow these movements to occur. We used the powerful owl (Ninox strenua), an urban apex predator in Melbourne, Australia, as a case study to understand their movement ecology in urban environments.
Owl movement was recorded using automated GPS logging devices deployed on ten powerful owls, resulting in 10870 GPS locations. In combination with these positions, four environmental covariates, and a priori understanding of owl ecology were used to assign movements to three different states (prey handling/eating, foraging and transitory) based on step length and turning angles between sequential locations in a hidden Markov model.
We demonstrate that the environmental covariate combination of time of night, Euclidean distance to riparian vegetation, and NDVI best described movement states. Owl movement states changed across the night. Shorter movements with many turns were made towards the beginning of the night in riparian areas with high NDVI. This behavior is most likely linked to prey handling, suggesting powerful owls are more likely to hunt early in the evenings and as such travel short distances while carrying large prey items. Transitory movements with limited changes in turning angles were the dominant movement state towards the end of the night. As owls leave areas of high NDVI, they quickly travel long distances across cleared land and impervious surfaces to connect to the next habitat patch where they then transition back into shorter step lengths where NDVI is higher.
This research highlights the critical importance of riparian vegetation and high NDVI areas in driving powerful owl movement and foraging in urban landscapes. Conservation priority should be placed on retaining and restoring riparian corridors as areas not only for powerful owls and their prey, but also for many other species that utilize similar resources.
... On some evenings, these mobbing bouts took place for up to 50 minutes and Noisy Miners were often attracted. Although owl(s) were noticeably disturbed by mixedspecies mobbing bouts, it did not necessarily eliminate their hunting capability, as we observed an adult owl in site C capture a Grey-headed Flying Fox Pteropus poliocephalus in the midst of such an event (described by Mo et al. 2015b). ...
Mobbing is an anti-predator strategy in which prey animals, notably birds and mammals, aggravate a
potential predator to either distract or drive them from the vicinity. The Powerful Owl Ninox strenua
is a large forest owl endemic to eastern Australia that preys mainly on arboreal mammals and birds.
We identified records of 30 species of birds and one mammal known to mob the Powerful Owl from
scientific literature and unpublished studies. In our study in southern Sydney, Powerful Owls were
most frequently mobbed by Noisy Miners Manorina melanocephala and Pied Currawongs Strepera
graculina, followed by Grey Butcherbirds Cracticus torquatus and Australian Magpies Cracticus tibicen. We
observed mobbing by three species of bird and one mammal that were not previously recorded as
mobbing species, including agonistic responses by a Tawny Frogmouth Podargus strigoides and Common
Brushtail Possum Trichosurus vulpecula during the time owls were active.
Several Powerful Owl Ninox strenua nest sites have been identified in pockets of bushland along the Georges River, southern Sydney (NSW), in the last four years (Bain et al. 2014; C. Lloyd et al. unpubl. data). We have been monitoring one particular breeding territory over the suburbs of Oatley and Hurstville Grove since 2012 (Mo & Waterhouse 2015; Mo et al. in press a,b,c). A nest hollow in a Smooth-barked Apple Angophora costata located in a vegetated gully had been used in three consecutive years. Each year, two fledglings were produced from this site. Our observations found that the owls resided at this nest site during the nesting and early post-fledgling period, retiring to a mangrove area in a second bushland remnant in the off-season (Mo et al. in press a).
The diet of the Powerful Owl has been well studied (Seebeck 1976; Tilley 1982; Traill 1993; Debus & Chafer 1994; Lavazanian et al. 1994; Pavey et al. 1994; Pavey 1995; McNabb 1996; Schulz 1997; Kavanagh 2002; Menkhorst et al. 2005; Cooke et al. 2006; Fitzsimons & Rose 2010; Olsen et al. 2011; Bilney 2013), primarily consisting of arboreal mammals and birds (Higgins et al. 1999). We recently reported a series of observations of successful kills by Powerful Owls recorded between 2012 and 2014 (Mo et al. in press b); however, there was one incident not described that antedates our scientific study. One moonless evening in the winter of 2000, one of us, Peter Hayler, was walking through a section of an urban remnant, which we now know as a nest site in our study. At around 2000 h, I stopped next to a eucalypt tree, which was ~1 m in diameter, leaning my arm against it. After ~15 minutes of total silence, a large bird had apparently smacked into the tree close to my hand. The noise from the abrupt action was similar to a brick being thrown at the tree trunk. The shock of the incident caused me to drop the beverage I was holding, and the bird was quick to fly away. The following morning, Peter Hayler revisited the site and found the carcass of a small Common Brushtail Possum Trichosurus vulpecula at the base of the tree where the incident occurred. This species has been frequently recorded in many dietary studies (e.g. McNabb 1996; Kavanagh 2002; Cooke et al. 2006; Olsen et
al. 2011; Bilney 2013), including ours (Mo & Waterhouse 2015; Mo et al. in press b). In hindsight, knowing that this site is the location of a nest hollow used by Powerful Owls and considering that no other nocturnal bird is likely to cause such a forceful incident, we believe a Powerful Owl had swooped at the tree. Local residents have since informed us that this species had been heard calling in the area for at least 15 years before our study. Actual observations of Powerful Owls catching prey are few in the scientific literature. Only two other authors have reported successful kills (Robinson 1968; McNabb 1996), and others reported unsuccessful hunting attempts (Hyem 1979; Chafer 1992; Olsen et al. 2011). If the incident reported here does indeed concern a Powerful Owl, then this account reveals further insight into the hunting strategy of this cryptic species. Despite the brief, ad hoc and isolated nature of the observation, it provides a dramatic comparison with our other observations of owl and prey contact, in which the killing was relatively quiet.
