Boobook Ninox Research Articles

Stable detection frequency of the threatened Christmas Island Boobook Ninox natalis, 2012–2022

ABSTRACT Both island species and raptors are at particularly high risk of extinction but few island raptor populations have been the subject of long-term monitoring. To determine trends in abundance in the Christmas Island Boobook, surveys were conducted annually from 2012–2017, in 2019 and in 2022. Across the survey period the population appears to have been either stable or to have increased slightly. Almost no part of the island lacked owls during the most recent survey. The detection rate averaged 1.56 (out of four surveys at a site); it was lowest in 2013 (1.22) and highest in 2022 (2.38). Detection was more likely on nights with low wind, at wetter sites and in closed vegetation, rather than in open or very low vegetation. In a separate analysis on the same data, the top-ranked dynamic occupancy-detection model found that occupancy increased with increasing elevation and vegetation height. No effect of a suspected threat, the presence of invasive yellow crazy ants Anoplolepis gracilipes at a site, could be detected. We recommend ongoing monitoring and research, potentially using automated recording devices and the tracking of individual owls to understand and refine the assumptions underpinning the interpretation of survey results.

Silent killers? The widespread exposure of predatory nocturnal birds to anticoagulant rodenticides

Anticoagulant rodenticides (ARs) influence predator populations and threaten the stability of ecosystems. Understanding the prevalence and impact of rodenticides in predators is crucial to inform conservation planning and policy. We collected dead birds of four nocturnal predatory species across differing landscapes: forests, agricultural, urban. Liver samples were analysed for eight ARs: three First Generation ARs (FGARs) and five SGARs (Second Generation ARs). We investigated interspecific differences in liver concentrations and whether landscape composition influenced this. FGARs were rarely detected, except pindone at low concentrations in powerful owls Ninox strenua. SGARs, however, were detected in every species and 92 % of birds analysed. Concentrations of SGARs were at levels where potential toxicological or lethal impacts would have occurred in 33 % of powerful owls, 68 % of tawny frogmouths Podargus strigoides, 42 % of southern boobooks N. bookbook and 80 % of barn owls Tyto javanica. When multiple SGARs were detected, the likelihood of potentially lethal concentrations of rodenticides increased. There was no association between landscape composition and SGAR exposure, or the presence of multiple SGARs, suggesting rodenticide poisoning is ubiquitous across all landscapes sampled. This widespread human-driven contamination in wildlife is a major threat to wildlife health. Given the high prevalence and concentrations of SGARs in these birds across all landscape types, we support the formal consideration of SGARs as a threatening process. Furthermore, given species that do not primarily eat rodents (tawny frogmouths, powerful owls) have comparable liver rodenticide concentrations to rodent predators (southern boobook, eastern barn owl), it appears there is broader contamination of the food-web than anticipated. We provide evidence that SGARs have the potential to pose a threat to the survival of avian predator populations. Given the functional importance of predators in ecosystems, combined with the animal welfare impacts of these chemicals, we propose governments should regulate the use of SGARs.

Characterization of a Near-Complete Genome Sequence of a Chaphamaparvovirus from an Australian Boobook Owl (Ninox boobook).

ABSTRACTThis study reports a complete genome sequence of a variant of psittacine chaphamaparvovirus 2 detected in kidney tissue from an Australian boobook (Ninox boobook), compiled using next-generation sequencing. The genome was 4,312 bp long, encoding four open reading frames. The detection of this variant in boobook represents a significant host-switching event.

Genome Sequence of a Beak and Feather Disease Virus from an Unusual Novel Host, Australian Boobook Owl (Ninox boobook).

ABSTRACTThe beak and feather disease virus (BFDV) is a pathogen of psittacine birds. BFDVs infecting nonpsittacine birds remain largely uncharacterized. We report the genome of a BFDV from a boobook owl (Ninox boobook), a nonpsittacine bird. The genome consisted of 1,993 bp containing two major bidirectionally transcribed open reading frames.

A recent specimen of a Tasmanian Boobook Ninox leucopsis recovered on Lord Howe Island

On 11 July 2019, during the Rodent Eradication Program on Lord Howe Island using aerial and ground rodentbaiting, the recovery of dead non-target birds included a recently dead boobook Ninox sp. found on a resident’s property. Two Tyto species were also recovered. Despite automated sound-recording equipment stationed within the forests of the Island, no records of Ninox vocalisations were made before discovery of the boobook specimen; however, two instances of Ninox owl calls were reported anecdotally within The Settlement. There was speculation from some Island residents that the recovered boobook could have been an individual of the extinct endemic subspecies, the Lord Howe Boobook N. novaeseelandiae albaria. The boobook was forwarded to the Australian Museum for further visual scrutiny, collection of morphometric data, DNA analysis, and preparation for the Australian Museum collection. There was overlap in plumage and morphological measurements between both the Tasmanian Boobook (N. leucopsis) and the nominate Tasman Morepork from New Zealand (N. n. novaeseelandiae), but the specimen was distinct from the larger Australian mainland N. boobook. DNA analysis provided conclusive evidence that the bird was a male N. leucopsis, exhibiting an overall clean-white spotted pattern and darker brown coloration. The occurrence of a Ninox species on Lord Howe Island is the first record in more than 50 years and should prompt further exploration of the dispersal and possible migration of boobooks from Tasmania.

Toxoplasma gondii seropositivity across urban and agricultural landscapes in an Australian owl

ABSTRACT In Australia, Toxoplasma gondii is an introduced parasite with a wide host range. House cats (Felis catus) are one of its definitive hosts. Little is known about T. gondii infection rates in Australian wildlife. Since cat abundance varies with landscape composition, we hypothesised that T. gondii infection would be more prevalent in urban and agricultural landscapes than intact bushland and sought to use samples from the Southern Boobook (Ninox boobook) as an indicator of ecosystem-wide T. gondii contamination. We used modified agglutination tests to determine T. gondii seropositivity in serum and meat juice samples taken from boobooks. Moderately low levels of seropositivity were detected and non-significant landscape-related patterns of seroprevalence were observed. We also examined correlations and interactions with owl age, season, injury status and exposure to an anticoagulant rodenticide. Only season showed significant correlations with observed seropositivity. To the best of our knowledge, this is the first published detection of T. gondii seropositivity in a wild predatory bird in Australia.

Widespread genetic connectivity in Australia’s most common owl, despite extensive habitat fragmentation

ABSTRACT Reductions in genetic diversity and genetic connectivity have been documented in some predatory bird species in response to anthropogenic habitat fragmentation. The Southern Boobook (Ninox boobook) is the most common and widely-distributed owl in Australia but declines in abundance have been observed across its range. We used polymorphic microsatellite loci to investigate landscape-scale patterns of genetic variation and spatial genetic structure in boobooks from a variety of fragmented landscape types and relatively undisturbed landscape types across Western Australia. The maximum distance between collection locations of genetic samples was 1391 km. Indirect estimates of connectivity inferred from these genetic data were complemented by direct estimates of post-breeding dispersal of juvenile boobooks gathered from banding data resulting from this and other studies across Australia. We found high genetic diversity in microsatellite markers, weak spatial genetic structuring and no evidence of genetic erosion associated with inbreeding in heavily fragmented landscapes. Bayesian modelling, spatial autocorrelation analysis and principal coordinates analysis suggested a single large panmictic population across all areas sampled. Within the heavily fragmented landscape of an extensive urban area, band re-sightings and recoveries substantiate the considerable capacity of juvenile boobooks to disperse across areas far greater than the distance between patches. We hypothesise that the genetic homogeneity observed in this species is a consequence of long-distance dispersal capacity in addition to their ability as habitat and dietary generalists to make use of highly altered habitats.

A comparison of urban and peri-urban/hinterland nocturnal birds at Brisbane, Australia

This study identified and compared the abundance and detectability of owls and other nocturnal birds, over 1 year, in an urban parkland of a Brisbane suburb to a peri-urban/hinterland/rainforest site 27km away. Five owl species were detected, but only at the peri-urban/hinterland/rainforest site, they were powerful owl Ninox strenua, southern boobook Ninox boobook, sooty owl, Tyto tenebricosa, masked owl Tyto novaehollandiae and barn owl Tyto alba. A single southern boobook was detected outside the study, at the urban site. The tawny frogmouth Podargus strigoides was only detected at the urban site whereas the plumed frogmouth Podargus ocellatus plumiferus was only detected at the rainforest site. The bush stone-curlew Burhinus grallarius was the most frequently detected nocturnal species, yet we discuss its recent decline in Brisbane. Incidentally recorded mammals, reptiles, frogs and diurnal birds are given. The rainforest site had more scansorial mammals whereas the urban site had more possums, dogs and cats.

Aerodynamic forces acting on birds during flight: A comparative study of a shorebird, songbird and a strigiform

The flapping wing is one of the most widespread propulsion methods found in nature. The current study focuses on the estimation of unsteady aerodynamic forces on freely flying birds through analysis of wingbeat kinematics and near wake flow measurements using long duration time-resolved particle image velocimetry. Three distinct bird species have been investigated: a shorebird (Western sandpiper, Calidris mauri), a songbird (European starling, Sturnus vulgaris) and a boobook owl (Australian boobook, Ninox boobook), corresponding to different flight strategies. Using long-time sampling data, several wingbeat cycles have been analyzed. Drag and lift were estimated using the momentum equation for viscous flows, revealing a highly unsteady behavior. The owl experienced the highest total drag over the cycle whilst the sandpiper was shown to exert minimal drag compared to the other two birds. The unsteady drag term was found to have a crucial role in the balance of drag (or thrust), particularly during the transition phases. The lift estimation presents a similar distribution over the wingbeat cycle, where both the owl and the sandpiper feature high values of unsteady lift compared to the starling. The large lift variation generated by the sandpiper is presumably used to achieve its high-performance migratory flight. For owls, the large variation of the lift appears to be essential for weight support while flying at slow speeds. The aerodynamic performance of the starling appears to be relatively low which matches their limited migratory behavior. These findings may shed light on the flight efficiency of birds by providing a partial answer to how they minimize drag and maximize lift during flapping flight by incorporating unsteady motion that interacts with the wake flow dynamics.

Flow Features of the Near Wake of the Australian Boobook Owl (Ninox boobook) During Flapping Flight Suggest an Aerodynamic Mechanism of Sound Suppression for Stealthy Flight.

SynopsisThe mechanisms associated with the ability of owls to fly silently have been the subject of scientific interest for many decades and may be relevant to bio-inspired design to reduce noise of flapping and non-flapping flying devices. Here, we characterize the near wake dynamics and the associated flow structures produced during flight of the Australian boobook owl (Ninox boobook). Three individual owls were flown at 8 ms−1 in a climatic avian wind tunnel. The velocity field in the wake was sampled at 500 Hz using long-duration high-speed particle image velocimetry (PIV) while the wing kinematics were imaged simultaneously using high speed video. The time series of velocity maps that were acquired over several consecutive wingbeat cycles enabled us to characterize the wake patterns and to associate them with the phases of the wingbeat cycle. We found that the owl wake was dramatically different from other birds measured under the same flow conditions (i.e., western sandpiper, Calidris mauri and European starling, Sturnus vulgaris). The near wake of the owl did not exhibit any apparent shedding of organized vortices. Instead, a more chaotic wake pattern was observed, in which the characteristic scales of vorticity (associated with turbulence) are substantially smaller in comparison to other birds. Estimating the pressure field developed in the wake shows that owls reduce the pressure Hessian (i.e., the pressure distribution) to approximately zero. We hypothesize that owls manipulate the near wake to suppress the aeroacoustic signal by controlling the size of vortices generated in the wake, which are associated with noise reduction through suppression of the pressure field. Understanding how specialized feather structures, wing morphology, or flight kinematics of owls contribute to this effect remains a challenge for additional study.

Anticoagulant rodenticide exposure in an Australian predatory bird increases with proximity to developed habitat

Anticoagulant rodenticides (ARs) are commonly used worldwide to control commensal rodents. Second generation anticoagulant rodenticides (SGARs) are highly persistent and have the potential to cause secondary poisoning in wildlife. To date no comprehensive assessment has been conducted on AR residues in Australian wildlife. My aim was to measure AR exposure in a common widespread owl species, the Southern Boobook (Ninox boobook) using boobooks found dead or moribund in order to assess the spatial distribution of this potential threat. A high percentage of boobooks were exposed (72.6%) and many showed potentially dangerous levels of AR residue (>0.1 mg/kg) in liver tissue (50.7%). Multiple rodenticides were detected in the livers of 38.4% of boobooks tested. Total liver concentration of ARs correlated positively with the proportions of developed areas around points where dead boobooks were recovered and negatively with proportions of agricultural and native land covers. Total AR concentration in livers correlated more closely with land use type at the spatial scale of a boobook's home range than at smaller or larger spatial scales. Two rodenticides not used by the public (difethialone and flocoumafen) were detected in boobooks indicating that professional use of ARs contributed to secondary exposure. Multiple ARs were also detected in recent fledglings, indicating probable exposure prior to fledging. Taken together, these results suggest that AR exposure poses a serious threat to native predators in Australia, particularly in species using urban and peri-urban areas and species with large home ranges.

Is there a link between eye colour and haemoparasite infection in the Southern Boobook Ninox boobook in the Perth Metropolitan Area?

The Southern Boobook Ninox boobook most commonly has a yellowish to greenish or greenish-hazel iris, but in the Perth Metropolitan Area a relatively high proportion of this species has eyes that range from a dark greenishbrown to dark brown. This trend seems to provide some initial evidence of an incipient genetic polymorphism within this population. The darker eye colour may also play a signalling role in sexual selection. An increase in disease consistent with haemosporidian infection has also been noted in recent years, possibly involving known Leucocytozoon or an aberrant Leucocytozoon -like species. Ongoing exposure to these parasites might have imposed selective pressure for increased resistance. Although this is explored here in some detail, it is possible that this phenomenon is associated with some other unidentified factor, or a combination of factors, so further investigation into this area may be rewarding.

Treatment of Traumatic Brain Injury in Morepork Owls: A Review of Diagnostic and Treatment Options

The Morepork (Ninox novaeseelandiae) is a small owl (150–200 g adult weight) of the family Strigidae. It is common throughout most of New Zealand and closely related to the Southern boobook (Ninox boobook) and Tasmanian boobook owls (Ninox leucopsis) found in Australia. Morepork are commonly presented to the Wildbase Hospital at Massey University, New Zealand. The vast majority of admissions are related to traumatic injuries with many showing some degree of neurological dysfunction. This review of case records indicates that only 35% of morepork admitted with a traumatic brain injury (TBI) recovered to the point of release. A failure to return to normal neurological function could be the result of direct trauma to neurological tissues acquired at the time of impact or ongoing damage with altered physiology compounding the initial trauma. While little can be done to treat primary brain insults, treatments that target minimizing secondary brain injury can improve the outcome of TBI. Diagnostic and treatment options for TBI in human and small animal medicine were reviewed for their potential application to avian medicine with the aim of improving treatment of TBI cases in morepork that will increase recovery rates and long term survival of birds returned to the wild.

Conservation status of threatened and endemic birds of New Britain, Papua New Guinea

SummaryNew Britain in the Bismarck Archipelago of Papua New Guinea supports 14 endemic bird species and together with New Ireland, forms an Endemic Bird Area that supports 38 restricted range species. Extensive conversion of lowland forest to oil palm plantations resulted in the loss of over 20% of forest under 100 m altitude between 1989 and 2000. However the rate of loss has subsequently slowed (2.2% loss across all altitudes between 2002 and 2014), and much forest remains at higher altitudes: 72% of New Britain remained forested (including secondary forest) in 2014. Despite the ongoing high threat and rich endemic bird fauna, the state of knowledge of the conservation status of birds in New Britain is very poor. We use an unprecedented dataset based on 415 hours of bird surveys conducted in oil palm plantations, as well as primary and secondary forests at all altitudes, to revise the IUCN status of New Britain’s birds. These data indicate that six species of elevated conservation concern are less dependent on old-growth forest than previously assessed. We recommend reduced population size estimates for one species, New Britain Kingfisher Todiramphus albonotatus. We recommend increased population size estimates for seven species: Pied Cuckoo-dove Reinwardtoena browni, Yellowish Imperial Pigeon Ducula subflavescens, Green-fronted Hanging Parrot Loriculus tener, Blue-eyed Cockatoo Cacatua opthalmica, Violaceous Coucal Centropus violaceous, New Britain Boobook Ninox odiosa and New Britain Thrush Zoothera talaseae. Despite our comprehensive surveys, Slaty-backed Goshawk Accipiter luteoschistaceus, New Britain Sparrowhawk Accipiter brachyurus, New Britain Bronzewing Henicophaps foersteri and Golden Masked-owl Tyto aurantia remain very rarely recorded and require further assessment. With ongoing habitat loss, particularly in lowland areas, New Britain’s birds urgently require more attention.

Winners and losers among mammals and nocturnal birds over 17 years in response to large-scale eucalypt plantation establishment on farmland

Large-scale plantations established for timber production can dramatically transform landscapes, however little is known about the response of more cryptic components of biodiversity. We report on trends in mammals and nocturnal birds during a 17year longitudinal study on three large-scale plantations of locally indigenous eucalypts in northern New South Wales, Australia. The study began in a farmland mosaic and has continued to track occupancy after the establishment of eucalypt plantations within the paddock areas. Surveys were undertaken at focal trees located in different classes of remnant vegetation that became embedded within the plantations as well as in the plantation matrix itself. Reference sites were also sampled in adjacent blocks of forest. We recorded nine species of arboreal mammals and eight species of nocturnal birds during focal tree watches, while camera and Elliott traps recorded 19 ground-dwelling taxa. Eleven of these species are listed as threatened. The majority of species were present, but uncommon, at the start of our study in the cleared farmland-remnant vegetation mosaic. Multi-season, multi-scale occupancy analyses revealed most species were stable over time and, among mammals, a large temporal increase was most notable for common brushtail possum Trichosurus vulpecula. A potential decline was only observed for eastern chestnut mouse Pseudomys gracilicaudatus, a trend also evident in other small mammals. Among nocturnal birds, both southern boobook Ninox boobook and Australian owlet nightjar Aegotheles cristatus increased in occupancy over time. Increasers tended to be widespread species with generalist attributes, while stable or decreasing species were more likely to be specialists. Few arboreal mammals or nocturnal birds were recorded in the plantation matrix itself, though some ground mammals (e.g., rufous bettong Aepyprymnus rufescens) had higher occupancy rates in plantation. Rather, most species were associated with remnant vegetation and old growth elements within plantations and these likely function as a refuge for fauna (potentially during plantation harvest), provide specialised resources such as tree hollows and facilitate the colonisation of plantations. While few negative effects due to change in land-use to plantation were recorded, limited increase in occupancy for most species contrasts with overall positive trends reported previously for diurnal bird species. Low structural complexity and tree species diversity within plantations are likely to limit the number of winners. In the context of a timber plantation, additional management to enhance recovery would best be directed to areas excluded from future harvesting, such as environmental plantings in degraded riparian zones and limiting livestock grazing. The ecosystem implications of increasing populations of generalists such as T. vulpecula remain unclear.

Can owls be used to monitor the impacts of urbanisation? A cautionary tale of variable detection

Context Due to their important ecological roles, predators are increasingly being suggested as targets for biodiversity studies investigating how they respond to landscape change and transformation. But there is limited literature investigating our capacity to accurately monitor changes in their occupancy. Aims To test the efficacy of playback surveys for monitoring owls as a basis for investigating change in owl occupancy over time. We ask whether playback is an effective tool, and whether it can be optimised to improve its utility. Methods Using the urban–forest interface of Melbourne, Australia, as a case study, we used playback techniques to survey for the presence of three owl species: the powerful owl (Ninox strenua); southern boobook (Ninox boobook); and eastern barn owl (Tyto javanica). Sites were repeat surveyed at least 16 times throughout the year and occupancy models were developed to establish how season and temperature influence nightly detection probabilities of owls. Key results All three species of owl were detected through playback survey approaches, but the detection probabilities varied greatly between species and across seasons and temperature conditions. Eastern barn owls are poor candidates for playback surveys due to their low detection probabilities. The southern boobook and powerful owl are responsive to playback, but detection probabilities are influenced by season and/or temperature conditions. To optimise survey approaches, southern boobooks should be surveyed during spring and summer and the powerful owl should be surveyed on nights where the minimum temperature is near 20°C. Conclusions Although there is considerable interest in using predators such as owls to monitor biodiversity impacts associated with landscape change, poor detection rates can limit their utility. However, optimising survey approaches that consider shifting detection probabilities under different conditions such as time of year or temperature may improve the utility of predators as surrogates in biodiversity monitoring. Implications Optimising survey approaches for owls considerably reduces the window of opportunity in which to conduct surveys. To counter this, the intensity of survey effort needs to be increased during key periods. The use of highly trained citizen science teams may be one effective way of delivering such an approach.

Owl survey of the Peel–Harvey Estuary in south-western Australia

Little is known of owls in south-western Australia compared with the owls of southern and eastern Australia. Surveys of forest owls in the south-west are almost completely lacking. This study sought to determine the abundance and detectability of owls immediately around the Peel–Harvey Estuary in south-western Australia. The southern boobook (Ninox boobook) and the masked owl (Tyto novaehollandiae) were the only owls detected (n = 23 and n = 1 respectively), although the nocturnal tawny frogmouth (Podargus strigoides) was detected from unelicited calls on three occasions. Southern boobooks were found to be common in this area though they are reported to be in decline in south-eastern and inland Australia. Their detectability was significantly greater in August (late winter) than at other times through unelicited calls; otherwise, there were no detections in winter. A variety of small mammals were detected during the surveys, including: a little red flying-fox (Pteropus scapulatus), a western ringtail possum (Pseudocheirus occidentalis), 19 southern brown bandicoots (Isoodon obesulus), 4 common brushtail possums (Trichosurus vulpecula), 21 rabbits (Oryctolagus cuniculus), a black rat (Rattus rattus), 2 red foxes (Vulpes vulpes) and 22 microbats.

Bioacoustic and multi-locus DNA data of Ninox owls support high incidence of extinction and recolonisation on small, low-lying islands across Wallacea

Known for their rich biodiversity and high level of endemism, the islands of Wallacea serve as natural laboratories for the study of spatio-temporal evolution and patterns of species diversification. Our study focuses on the owl genus Ninox, particularly the Southern Boobook (N. novaeseelandiae) and Moluccan Boobook (N. squamipila) complexes, which are widely distributed across Australasia. We conducted bioacoustic and multi-locus DNA analyses of 24 Ninox owl taxa to evaluate relationships and levels of divergence within the two complexes and ultimately assess the relationship between patterns of taxonomic differentiation and bioclimatic factors. We found that taxa that are vocally and/or genetically distinct from populations on the Australian mainland are found on islands that are significantly larger and higher in altitude than taxa that are vocally and/or genetically indistinct from populations on the Australian mainland. This pattern suggests that taxa occurring on small, low-lying Wallacean islands are likely to be recent colonisers that have dispersed from Australia. Overall, our observations demonstrate that the genus Ninox is likely to have colonised the Wallacean region multiple times as small, low-lying islands undergo frequent extinction, whereas populations on large and high-altitude islands are more resilient.

Night for Day: Anticipating Environmental Futures Through Contemporary Art

Presented in the form of an image essay, the mixed media installation Night for Day (The Owl of Bunbury spreads its wings only with the falling of the dusk) (2015) is described and briefly contextualized in relation to more-than-human worlds, local histories and stories, sea level change, and other Anthropogenic trajectories. To create the artwork, the artist explored historical and predicted flooding events in the regional town of Bunbury, Western Australia. She combined, transformed, reconstituted, and rearranged data and material things in a process of investigating how futures might be imagined and anticipated. Representations of southern boobook owls (Ninox novaeseelandiae) made from rainfall maps fly across the installation. Water from Leschenault Inlet (part of Derbal Elaap) was brought into the gallery space. The overall poetics and affective register of material elements of the installation are enhanced by being presented as full spread images.

Common Mynas attack Common Brushtail Possums and nesting Southern Boobook, and diet of the nesting Boobooks

Over a 30-night period a Common Myna Acridotheres tristis was observed attacking Common Brushtail Possums Trichosurus vulpecula and harassing a female Southern Boobook Ninox boobook near her nest. One night a Myna that had been attacking Possums was chased by the male Boobook, which appeared to be chasing it as prey. We did not observe further attacks by Mynas after this night. Common Mynas were found in the dietary analysis for this pair of Boobooks.