Article

Response of a cryptic apex predator to a complete urban to forest gradient

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Abstract

Context. Urbanisation is one of the most damaging landscape-scale disturbance processes leading to significant and potentially irreversible changes in biodiversity. How apex predators respond to urbanisation is poorly understood, largely because of their low density and low detectability. Given the important functional roles of apex predators in ecosystems, it is critical that research investigates how they respond to urbanisation, and how urban systems can be designed to better support apex predators. Aims. The present research aims to examine how an avian apex predator, the powerful owl, responds to a complete urban–forest gradient in southern Victoria, Australia. Specifically, the research aims to understand the environmental attributes that drive habitat suitability for powerful owls across the urban–forest gradient. Methods. Using a total of 683 independent field-and atlas-derived records of powerful owls across the study site, the research takes a presence-only modelling approach. The presence points were modelled against a series of geospatial variables that were determined a priori on the basis of the known ecology of powerful owls. Key results. Potential powerful owl habitat declined in a dramatic fashion in response to increasing levels of urbanisation, ranging from 76% of the forest landscape to 21% of the urban landscape. Powerful owl habitat availability across the urban–forest gradient is positively influenced by tree cover, productivity (normalised difference vegetation index) and proximity to river systems and riparian vegetation. Conclusions. Presence-only modelling has provided a useful way for investigating the response of an apex predator to a gradient of urbanisation. Although powerful owl habitat availability is negatively reduced by urbanisation, there is significant scope to manage urban landscapes to either maintain or improve the availability of habitat across the gradient. Implications. High resource-requiring species, such as apex predators, have the capacity to be detrimentally affected by urbanisation processes. Presence-only modelling, however, provides a useful tool for investigating how these difficult-to-detect species are affected by urbanisation, and ultimately inform how landscapes can be managed to maximise habitat availability for apex predators.

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... This species has, however, been identified as inhabiting urban environments in close proximity to Melbourne (Cooke et al., 2002a), Sydney (Kavanagh, 2004) and Brisbane (Pavey, 1993). Along the east coast of Australia this species has been linked to certain ecological requirements, including structurally complex vegetation communities for suitable roosting and nesting sites, adequate water sources and a suitable prey base (Tilley, 1982;Kavanagh and Peake, 1993;Pavey, 1993;Loyn et al., 2001;Cooke et al., 2002b;Kavanagh, 2004;Isaac et al., 2008;Isaac et al., 2013). ...
... Supplementary presences were not utilized in the modeling of tree cavities. Presences, were used to model habitat suitability for the aforementioned species across the urban to forest gradient (Isaac, 2012;Isaac et al., 2013Isaac et al., , 2014. ...
... To produce layers for MCDA from the output of the habitat suitability maps for the powerful owl (Isaac et al., 2013), disturbanceintolerant arboreal marsupials, arboreal marsupials tolerant to moderate disturbance, disturbance-tolerant marsupials (Isaac et al., 2014) and large tree hollows (Isaac, 2012) we used ArcGIS 10.0. We re-classed all models to include only potential habitat. ...
... In comparison to diurnal species, the ecological response of nocturnal birds to urbanization has not been well studied because of their low density and detectability (Weaving et al. 2011;Isaac et al. 2013;Fröhlich and Ciach 2019). Among nocturnal birds, owls are particularly interesting given their role as top predators in most terrestrial habitats, with their presence often being related to ecosystem quality (Isaac et al. 2013;Fröhlich and Ciach 2019). ...
... In comparison to diurnal species, the ecological response of nocturnal birds to urbanization has not been well studied because of their low density and detectability (Weaving et al. 2011;Isaac et al. 2013;Fröhlich and Ciach 2019). Among nocturnal birds, owls are particularly interesting given their role as top predators in most terrestrial habitats, with their presence often being related to ecosystem quality (Isaac et al. 2013;Fröhlich and Ciach 2019). Actually, in some urban areas owls have been identified as important biological control agents of rodent pests (Saufi et al. 2020). ...
... This result shows that the behavioral context (i.e., territoriality and mate attraction) could drive the vocal output instead of noise-light pollution, as suggested by Fröhlich and Ciach (2018). The positive relationship we found between green cover and the presence of the Mottled Owl agrees with findings for other owls, such as the Powerful Owl (Ninox strenua), Tawny Owl (Strix aluco), Barred Owl (Strix varia), and Great Horned Owl (Bubo virginianus) for which tree cover positively influenced habitat availability (Ranazzi et al. 2000;Isaac et al. 2013;Rullman and Marzluff 2014). ...
Article
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Background: Cities differ from non-urban environments by the intensity, scale, and extent of anthropogenic pressures, which can drive the occurrence, physiology, and behavior of the organisms thriving in these settings. Traits as green cover often predict the occurrence patterns of bird species in urban areas. Yet, anthropogenic noise and artificial light at night (ALAN) could also limit the presence and disrupt the behavior of birds. However, there is still a dearth of knowledge about the influence of urbanization through noise and light pollution on nocturnal bird species ecology. In this study, we assessed the role of green cover, noise, and light pollution on the occurrence and vocal activity of the Mottled Owl (Ciccaba virgata) in the city of Xalapa (Mexico). Methods: We obtained soundscape recordings in 61 independent sites scattered across the city of Xalapa using autonomous recording units. We performed a semi-automated acoustic analysis of the recordings, corroborating all Mottled Owl vocalizations. We calculated two measures of anthropogenic noise at each study site: daily noise (during 24 h) and masking noise (mean noise amplitude at night per site that could mask the owl's vocalizations). We further performed generalized linear models to relate green cover, ALAN, daily noise, and masking noise in relation to the owl's occurrence (i.e., detected, undetected). We also ran linear models to assess relationships among the beginning and ending of vocal activity with ALAN, and with the anthropogenic and masking noise levels at the moment of which vocalizations were emitted. Finally, we explored variations of the vocal activity of the Mottled Owl measured as vocalization rate across time. Results: The presence of Mottled Owls increased with the size of green cover and decreased with increases in both artificial light at night and noise levels. At the temporal scale, green cover was positively related with the ending of the owl's vocal activity, while daily noise and ALAN levels were not related to the timing and vocal output (i.e., number of vocalizations). Furthermore, the Mottled Owl showed a marked peak of vocal activity before dawn than after dusk. Although anthropogenic noise levels varied significantly across the assessed time, we did not find an association between high vocal output during time periods with lower noise levels. Conclusions: Spatially, green cover area was positively related with the presence of the Mottled Owl in Xalapa, while high noise and light pollution were related to its absence. At a temporal scale, daily noise and ALAN levels were not related with the timing and vocal output. This suggests that instead of environmental factors, behavioral contexts such as territoriality and mate interactions could drive the vocal activity of the Mottled Owl. Further studies need to incorporate a wider seasonal scale in order to explore the variation of different vocalizations of this species in relation to environmental and biological factors. Keywords: Anthropogenic noise, Acoustic monitoring, Nighttime ecology, Urban ecology, Urbanization, Vocal activity
... Additional records were sourced from BirdLife Australia's citizen science "Melbourne Powerful Owl Project". New records were combined with presences from Isaac et al. (2013) in ArcGIS version 10.2.2 (ESRI, 2014). Presence records collected prior to 1997 were removed to limit historical environmental change and any duplicate presences (i.e. ...
... Environmental layers originally collated by Isaac et al. (2013) were selected based on a priori understanding of powerful owl ecology. Ecogeographical variables used for modelling included lineal density of ephemeral and permanent rivers, Euclidean distance to riparian areas, riparian vegetation, slope position classification, Normalised Difference Vegetation Index (NDVI), land cover and density of tree cover (Table 1). ...
... The parameters that we varied were the regularization betamultipliers at 0.5, 1, 2, 3, 4 and 5, and the features, using combinations of linear, quadratic, product, threshold and hinge. We did not include a bias file, as it was demonstrated to have very little influence on the overall fit of the data for the powerful owl in previous modelling (Isaac et al., 2013). Each model was run in raw format with 20 replicates at 5000 iterations. ...
Article
Apex predators are critical to ecological function, however their life history traits are often not conducive to survival in urban environments. While this can result in the loss of some apex predators, others are able to inhabit and utilize urban environments. Understanding predator resource requirements and the factors driving their distribution is often difficult due to their cryptic nature, however, this understanding is essential, given the current rate of urban expansion. In this research we use a threatened apex predator, the powerful owl (Ninox strenua) as a case study. Specifically, we aim to (1) develop a Species Distribution Model (SDM) to ascertain environmental variables driving habitat suitability across an urban gradient (2) determine fine scale spatial movements of powerful owls using GPS telemetry; (3) validate the SDM against collected GPS movement data; and (4) evaluate habitat predicted by the SDM against current reserve systems to establish whether they are adequate for the future protection of this species. We used MaxEnt and citizen science data to produce SDMs that predicted habitat suitability for powerful owls and identified the environmental variables driving habitat across the landscape. Fine-scale spatial movements for urban powerful owls, gained via GPS telemetry, were used to establish home-range sizes, validate models and assess the fit of telemetry data against SDM predictions. Rivers, vegetation (particularly dense tree cover) and distance to riparian areas were the ecological variables driving predicted habitat for powerful owls across the urban gradient. There was a strong relationship between habitat predicted by the SDM and the fine scale movements of powerful owls in urbanized environments. Home-ranges within this urban study were notably smaller than previous estimates established for forested environments. The powerful owls in our study were also shown to utilize considerable amounts of habitat outside of the reserve system. This has severe conservation implications because it is often the space outside of reserves that are at most risk from urban intensification. Conservation of the powerful owl in urban environments, therefore, needs to focus on both habitat management within existing reserves, and on establishing clear vegetation management strategies in the surrounding urban matrix.
... Presence surveys were undertaken across Melbourne and focussed on areas with confirmed powerful owl sightings from atlas data and previous research by Cooke (2000) and Isaac et al. (2013). Determining presence of powerful owls involved both day and night surveys. ...
... Day surveys targeted areas of high tree cover in gullies and along rivers and streams. These areas were targeted as powerful owls are known to regularly roost in such habitats (McNabb, 1996;Cooke et al. 2002a;Isaac et al. 2013). ...
... We predicted that owls would more frequently be in prey handling and foraging states in areas of higher vegetation productivity (i.e. high NDVI) and near rivers (Isaac et al. 2013;Bradsworth et al. 2017). As these areas of the landscape are also generally where the owls roost, we also predicted that prey handling and foraging movements would be made at the beginning of the night as they emerge from roosting. ...
Article
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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.
... 8 Pairs that fail during their initial breeding attempt will abandon the nest without any further attempts until the next year. 4,27,17 Powerful owls will breed in urban areas; however, a lack of suitable breeding hollows 28,19 and increased disturbance levels 29 are their greatest limiting factors. Where suitable hollows are present in urban areas, powerful owls have bred successfully, with young fledging over consecutive years in parklands less than 20 km from Melbourne's central business district. ...
... We employed measures to restrict spatial and historical biases associated with presence data derived from atlas datasets. 28 We selected or derived eco-geographical variables (EGVs) based on the ecology of the owl or prey species. Models incorporated both default and alternate settings where ecologically applicable. ...
... Initial modeling for the powerful owl indicated the importance of vegetated environments, particularly those in close proximity to riparian systems, for the occurrence of this species. 28 Additional analysis showed that forests and urban-fringe environments are capable of supporting enough potential habitat for powerful owls to successfully forage, roost, and nest, but urban areas of the gradient provide only limited and highly scattered patches of potential habitat for this species. This suggests a decline in potential habitat as urbanization intensifies. ...
Chapter
Once thought to live only in large forested areas, the powerful owl (Ninox strenua), Australia’s largest and most iconic of owls (figure 11.1), surprisingly is now turning up frequently in the cities of eastern Australia. Powerful owls require ample prey and large tree cavities for nest sites; how this top-order predator is able to survive in human-dominated landscapes is an important question for conservation and the focus of ongoing research. The powerful owl is endemic to Australia, resident in the three eastern mainland states and the Australian Capital Territory, and classified nationally as “rare.”2,3 First described by Gould in 1838, powerful owls are an unusual raptor in that they do not exhibit reversed sexual size dimorphism, the prevalent trait among raptors in which females are larger than males. For reasons still not understood, male powerful owls grow to a height of 65 cm and weigh up to 1,700 g, compared to females, which grow to a height of 54 cm and weigh up to 1,308 g.1
... The LANDCOVER layer was derived from highresolution optical imagery (SPOT 5) with the classifications depicting land-use and vegetation cover, categorised into five categories: tree cover, grass/ agricultural cropping, rivers/waterways, waterbodies and impervious surfaces (representing urban) (Isaac et al. 2013). The latter captures features distinct to urban areas, such as roads and buildings. ...
... We included the unprocessed NDVI variable because it represents a continuum of vegetation productivity across the landscape. RIPARIAN indicates the presence of riparian-associated vegetation communities only, extracted from state-wide mapping of 'ecological vegetation classes' (Isaac et al. 2013). We included TPI and SPC which describe topography and slope, respectively, and indicate the presence of gullies. ...
... MAXENT provides a raw output that indicates the relative predicted probability of the presence of a species at each pixel, which can be re-scaled and interpreted as an indication of suitable habitat. With due caution for the possible loss of information (see Guillera-Arroita et al. 2015), we created a binary habitat map using the 10th percentile threshold, a commonly used (Razgour et al. 2011;Isaac et al. 2013) and conservative threshold that maximises diagnosticity. ...
Article
Local native species that decline in response to urbanisation are often classified as ‘urban avoiders’. Their decline drives the biotic homogenisation seen in cities but the characterisation of these species as urban avoiders may discourage efforts to conserve them in urban landscapes. We used gradient analysis and species distribution modelling to examine habitat availability and fragmentation along an entire urban-forest gradient for a representative urban avoider – the Eastern Yellow Robin (Eopsaltria australis). Gradient analysis had utility in quantifying threats for this species but species distribution modelling better highlighted conservation opportunities in the landscape. The amount of suitable habitat declined with increasing urbanisation whilst fragmentation increased. Towards the city centre, habitat clustered around major waterways. Riparian networks showed clear potential to facilitate the restoration of connectivity between urban and fringing habitat and we identify ‘missing links’ in this network – key opportunities for habitat restoration. Riparian vegetation escapes development, is the preferred habitat for many species, including humans, and can serve as the logical architecture on which to focus conservation efforts. Restoring habitat along riparian networks in cities can build comprehensive and fully connected biotic infrastructure that facilitates human-nature connections and conserves local native species diversity.
... The nocturnal, and non-migratory powerful owl (Ninox strenua) is one of the few native apex predators persisting within urban environments of eastern Australia. Traditionally viewed as an old growth forestdependent species (Debus & Chafer, 1994;McNabb, 1996), the powerful owl is adaptable in utilising human-dominated landscapes such as urban parks at low densities where suitable habitat exists (Cooke et al., 2018;Isaac et al., 2013;Kavanagh, 2004;Webster et al., 1999;Pavey, 1995). Deforestation through forestry practices, urbanisation and bushfires have caused an ongoing population decline where it is now listed as 'vulnerable' under state legislation in Victoria, New South Wales and Queensland (Higgins 1999). ...
... This research was undertaken in Greater Melbourne, Victoria (37 • 49 ′ S, 144 • 58 ′ E), Australia's second largest city. Powerful owls are known to use a variety of habitat types throughout the Greater Melbourne region including urban, suburban, agricultural, and forested environments (Bradsworth et al., 2017;Carter et al., 2019;Cooke et al., 2002;Isaac et al., 2013). Melbourne, like many cities in the world, has high density housing close to the city centre, with housing density declining as it expands towards the urban fringe where it abuts protected forest environments and agriculture. ...
Article
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As landscapes are increasingly modified due to anthropogenic processes such as urbanisation or development for agriculture, the need to understand wildlife habitat requirements is imperative. This is particularly pertinent for species that are threatened, or apex predators with specific nest, den, or food requirements. Identifying responses to habitat with thresholds can provide an understanding of what resources species are using or avoiding, and their interactions with the surrounding environment. In this research we investigated space use and habitat requirements of the threatened apex predator, the powerful owl (Ninox strenua) in Greater Melbourne, Australia. We deployed GPS devices to 21 urban powerful owls over five years and found owls had an average home range size of 397 ha, and an average core-range of 84 ha. Home range size and positioning was driven by tree cover and urban land cover, while core ranges were restricted to treed environments with a limited area of impervious surfaces and housing. We used thresholds to identify-three priorities for powerful owl conservation in Mel-bourne. Priority 1: Ensuring river corridors and public open spaces are adequately protected. Priority 2: Limit property densities near rivers and protected areas. Priority 3: Finding opportunities for revegetation to expand and enhance habitat over time. Our research demonstrates how species-specific thresholds can inform land use planning to ensure wildlife species are maintained within highly modified environments.
... We established boundaries between the urban to urbanfringe and urban-fringe to forest zones to form clear transitional zones for post-proportional analysis.These boundaries were digitized based on coverage of impervious surfaces and trees using a land cover layer we derived from SPOT 5 satellite imagery (Systèm Pour l'Observation de la Terre; Isaac et al. 2013;2014;Fig. 1). Pixels at a scale of 20 m × 20 m were classified as impervious surfaces, tree cover, grass/agriculture, water or rivers based on spectral reflectance values. ...
... Layers produced for modelling included the density of ephemeral rivers, permanent rivers and roads, tree cover, riparian vegetation, Euclidean distance to riparian vegetation, slope position classification (SPC), normalized difference vegetation index (NDVI) and land cover ( Table 2). The NDVI and land cover layers were both derived from SPOT 5 satellite imagery (Isaac et al. 2013;2014). Eco-geographical variables had a spatial resolution of 20 m × 20 m and Fig. 1. ...
Article
Resource availability is a limiting factor influencing the distribution and composition of faunal communities. Globally, hollow bearing trees are a resource required by wildlife at all trophic levels, and are used for a diverse range of ecological functions. In the northern hemisphere avian species act as primary hollow excavators, whereas the southern hemisphere must rely on complex interactions between stochastic events, and eventual decay. Hollow formation is therefore a slow process in the southern hemisphere. In contrast, hollow loss is quite rapid and influenced greatly by anthropogenic impacts. To identify the ecological characteristics driving hollows over an urban to forest gradient as a resource for the powerful owl (Ninox strenua) and its prey we used presence-only modelling. The potential for an area to support tree hollows suitable for powerful owls and their prey was linked to the density of ephemeral rivers, land cover, tree cover and distance from riparian vegetation. The potential for large hollows throughout the landscape, suitable for the powerful owl, was also influenced by density of permanent rivers. Potential habitat for tree hollows, capable of supporting powerful owls and their prey was greatest in forested environments, declining with increased urbanization. However the urban region still supported some smaller tree hollows suitable for arboreal marsupials. Managing for urban dwelling species, is not as simple as retaining old hollow producing trees or providing alternate nesting structures. We also need to mitigate increased mortality associated with built environments (e.g. electrocution, collisions).
... Research examining nocturnal bird species response to gradients of urbanization have occurred less frequently. Notable exceptions include research investigating various ecological requirements of the powerful owl (Ninox strenua) an iconic Australian apex predator (Cooke et al. 2006;Cooke, Wallis and Webster 2002;Isaac et al. 2013). ...
... The consequences of the "sharing" model for urban-avoider species however, would be high, as many demonstrate a reliance on the habitat values provided by native remnant vegetation. (Isaac et al. 2013 In particular there is very limited research at a city scale as to how both urban-growth scenarios will impact on biodiversity (Sushinsky et al. 2013). Assessing these impacts will require long-term and targeted urban ecological research with a view that research findings will underpin future urban planning policies and urban development. ...
Thesis
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The tawny frogmouth is a nocturnal bird species endemic to Australia. While many species of wildlife worldwide experience detrimental outcomes from urbanization, this thesis demonstrates the resilience and adaptability of this unique species to landscape change by human beings.
... Due to its consistently competitive performance compared to other classical, more established presence-only and machine learning techniques (Elith et al. 2006, Gastón andGarcía-Viñas 2011), MaxEnt has gained prominence in wildlife research and is seeing a rapidly growing number of applications in studies of both v www.esajournals.org terrestrial and marine mobile mega-vertebrates such as sharks (Dambach andRö dder 2011, Sequeira et al. 2012), seabirds (Friedlaender et al. 2011), turtles (McClellan et al. 2014, dolphins (Thorne et al. 2012, Gomez andCassini 2015), baleen whales (Bombosch et al. 2014), leopards (McCarthy et al. 2015, falcons (Kassara et al. 2012), owls (Carroll 2010, Isaac et al. 2013, foxes (Cleve et al. 2011), or African wild dogs (Whittington-Jones et al. 2014), among many other examples. MaxEnt is founded ''on the bedrock of probability theory'' (Brierley et al. 2003), and a complete description of the mechanics underlying the algorithm is given by and Baldwin (2009). ...
Article
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We present a novel system of drifting pelagic baited stereo-video cameras that operate in deep-water, topographically complex environments typically considered inaccessible for sampling. The instruments are portable, semi-autonomous and inexpensive, allowing the recording of high-definition video footage in near-real time and over broad stretches of ocean space. We illustrate their benefits and potential as non-extractive monitoring tools for offshore marine reserves with a pilot study conducted within the newly established Perth Canyon Commonwealth Marine Reserve, southwestern Australia (32 S, 115 E). Using occupancy and maximum entropy models, we predict the distribution of midwater fishes and sharks and show that their most suitable habitat encompasses a wider fraction of the canyon head than is covered by park boundaries. Our proof-of-concept study demonstrates that drifting pelagic stereo-video cameras can serve as appropriate field platforms for the construction of species distribution models with implications for ocean zoning and conservation planning efforts.
... Similarly, small-sized raptor species are more able to adapt to the fragmented urban landscape than larger species (Chace & Walsh, 2006). By considering the preferences of sensitive raptors, particularly those of threatened species, landscape planning strategies can be optimised to enable the richest biodiversity and conservation benefits (Cade, Martell, Redig, Septon, & Tordoff, 1996;Simmons, Rodrigues, Woodcock, Steyn, & Jenkins, 2007;Sanderson & Huron, 2011;Isaac, White, Ierodiaconou, & Cooke, 2013). ...
... The Powerful Owl Ninox strenua has been extensively studied in a range of forest types (Debus & Chafer 1994;Higgins 1999), including modified landscapes (Cooke et al. 2002a,b;McNabb 2004;Isaac et al. 2013). Many behavioural studies have focussed on diet and hunting (Kavanagh 2002;Menkhorst et al. 2005;Fitzsimons & Rose 2010;Olsen et al. 2011), breeding success (Lavazanian et al. 1994;Pavey et al. 1994;McNabb 1996;Hogan & Cooke 2010) and roost preferences (Pavey & Smyth 1998;Webster et al. 1999;Menkhorst et al. 2005). ...
Article
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This paper describes an account of combat between two Powerful Owls Ninox strenua in the St George area, Sydney, NSW. The breeding pair of this territory had been followed as part of a monitoring program since July 2012. Daily photographic records from February to May 2014 provided recognition of individual birds by observing their distinctive chest patterns. Two possible interpretations of the incident were generated. Based on the identity of the aggressor and a male changeover in the territory, the combat incident was believed to be a contest between rival males.
... The Brown Goshawk can be considered a habitat generalist as it is able to occupy a variety of habitats, wherever trees or tall shrubs provide cover for ambushing prey (Marchant & Higgins 1993). Urbanisation of an environment tends to favour increased densities of generalist species (Devictor et al. 2008;Isaac et al. 2013) as they are able to exploit the heterogeneity created. Generalists that use a greater variety of habitats are also less affected by habitat fragmentation than specialist species. ...
Article
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The breeding parameters of the Brown Goshawk (Accipiter fasciatus) have yet to be documented in an urban environment in Australia. Twenty-six active nests were located in urban Darwin during the 2013–2014 breeding season. Incubation occurred from August to November over a 12 week laying period. Twenty-two nests were in introduced African Mahogany trees (Khaya senegalensis) and four were in River Red Gums (Eucalyptus camaldulensis). One or more young matured to fledgling stage or later at 17 of the 26 nests, with an average fledging rate of 1.13 young per nest. Assuming that all active nests were detected, the breeding density of Brown Goshawks across the study area is 52 nests per 100 km 2 , which is higher than that recorded in previous studies on the species.
... through a case study which provided artificial cavities for the powerful owl, Ninox strenua. The powerful owl is a nocturnal raptor that inhabits a range of habitats in south-eastern Australia, including relatively undisturbed forests and urban environments(Bradsworth et al., 2017;Isaac et al., 2013). Powerful owls are listed as threatened in the southern parts of their range (Department of Environment, Land, Water and Planning, 2019), where the loss of large, cavity-bearing trees is the primary negative impact(Isaac et al., 2014). ...
Article
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The decline of critical habitat structures, such as large old trees, is a global environmental challenge. The cavities that occur in these trees provide shelter and nesting sites for many species but can take centuries to develop. Artificial cavities, including nest boxes and carved logs, offer an increasingly important conservation response. However, current methods of designing, manufacturing and deploying such habitats have constraints that limit innovation, feasibility and effectiveness. In response, this article aims to provide new and broadly useable methods that can improve the design of habitat structures for cavity‐dependent animals. To address the shortcomings of existing methods, we develop an approach that uses computer‐aided design techniques of generative and parametric modelling to produce structures that satisfy stakeholder needs, computer‐aided manufacturing techniques of 3D printing and augmented‐reality assembly to build functional prototypes, and computer‐assisted techniques of laser scanning and data‐driven design to support installation, monitoring and iterative improvement of designs. We demonstrate this approach through a case‐study project that designs and instals habitat structures for the powerful owl Ninox strenua, a cavity‐dependent and threatened bird. Through a comparison with existing methods, our pilot study shows that computer‐aided design and manufacturing can provide novel and useful approaches to develop artificial habitat‐structures. Computer‐aided design finds geometries that approximate the complex characteristics of natural tree cavities and automatically produces new versions to suit diverse sites or species. Computer‐aided manufacturing integrates materials that match the performance of naturally occurring habitat structures and facilitates the assembly of complex geometries by non‐experts. Computer‐assisted techniques produce precisely fitting and easy‐to‐instal designs, which support gradual improvement through ongoing prototyping and evaluation. These capabilities highlight how advanced design techniques can improve aspects of artificial habitat‐structures through geometric innovation, novel construction techniques and iterative exploration. Significantly, computational approaches can result in designs that can perform well, are easy to construct and instal and are applicable in many situations. Our reusable workflow can aid in the tasks of practical conservation and support ecological research by effectively negotiating the needs of both humans and target species.
... The increase in human population size, and the consequent increased needs for food, shelter and other products, has led to an unparalleled increase in the rates at which natural environments are transformed into agricultural lands, plantations and urban areas (Foley et al., 2014). Among the different forms of landscape modification by humans, urbanisation is arguably the most damaging, persistent and rapidly expanding across the globe, leading to the loss of a larger share of native biodiversity (McKinney, 2002;Mahan and O'Connell, 2005;McKinney, 2006;Tremblay and St Clair, 2011;Isaac et al., 2013). This has led to the growth of urban areas since the second half of the 20 th century to be considered the single greatest threat to biodiversity worldwide (Grimm et al., 2008;Elmqvist et al., 2013). ...
Article
Urbanisation is one of the most rapidly expanding forms of landscape modification by humans and leads to large-scale loss and fragmentation of native habitat. This can alter the structure, composition and function of remnant habitat. Therefore, understanding the influence of both landscape and patch characteristics is important for understanding factors affecting the distribution of organisms in urbanised landscapes. Consequently, the aim of this study was to establish the responses of forest dwelling mammals to landscape and habitat structure in an urban-forest mosaic in the EThekwini Municipality Area, Durban, South Africa. Using presence and absence data of mammals from camera traps, we modelled occupancy of species using the occupancy modelling framework. The occupancy by Philantomba monticola was positively influenced by forest cover (%), woody cover (%), leaf litter (%) and stem density of large trees and negatively influenced by road density. For Tragelaphus sylvaticus, Potamochoerus larvatus and Hystix africaeaustralis, occupancy was influenced positively by forest cover (%), woody cover (%) and foliage height diversity and negatively influenced by road density. For Genetta tigrina and Chlorocebus pygerythrus, occupancy was positively influenced by leaf litter (%), woody cover (%), forest cover (%) and road density and negatively influenced by distance to road. Thus, species showed varying responses to landscape and habitat structural variables. Genetta tigrina and C. pygerythrus appeared less vulnerable to the loss of forest habitat and degradation in habitat quality whereas T. sylvaticus, P. larvatus and H. africaeaustralis showed strong negative responses to such changes. The semi-arboreal habits of G. tigrina and C. pygerythrus may be an important factor facilitating their adaptability to urban environments as they can move unimpededly across the urban landscape in search of resources. The diversity of responses suggests that landscape management approaches that consider the habitat requirements of multiple species are more likely to be successful in this landscape. We suggest that conservation efforts directed primarily towards the protection and restoration of structurally intact forest habitats is the most prudent strategy for the conservation of mammalian diversity in this landscape.
... 24 This may be due in part to the low densities, large spatial requirements, and cryptic behaviors of many raptor species. 24,65 Recent technologies that make use of spatial modeling programs, including FRAGSTATS, 66 Geospatial Modeling Environment (GME), 67 and Geographical Information System (GIS), 68 have become increasingly important tools in raptor research. Using these technologies coupled with data obtained through field techniques such as radiotelemetry and direct observation, researchers have been able to analyze the effects of multiple land-use types on the spatial ecology of a species. ...
Chapter
Urbanization presents a major global issue for the conservation and survival of many different species. With the increasing footprint of cities and intensification of our use of urban areas, wildlife faces extremely difficult challenges to live there. Understanding how species respond to urban processes and how to design urban landscapes that facilitate species’ presences are major emerging research and management priorities. Despite general negative responses to increasing urbanization, some animal taxa, both native and introduced, appear to benefit from urban environments by capitalizing on novel environments and abundant resources.¹ Those that are common in urban systems display particular physical characteristics and ecological traits.2,3,4 They also frequently display a level of behavioral plasticity or tolerance, adjusting their behavior to interact with, and survive in, urban environments.5,6 Termed urban-adaptors,⁷ these species may exhibit altered spatial,8,9,10 foraging,11,12 and breeding behaviors,¹³ as detailed in chapter 2.
... As urban populations increase, the development of urban land is continuing to accelerate. Rapid urban development and large-scale urban expansion have caused many adverse effects on urban biodiversity (Isaac et al. 2013;Schueller et al. 2019) as well as the ecosystem services it provides (Brunori et al. 2017). One of the central threats to urban biodiversity is the fragmentation and heterogeneity of the urban landscape caused by changes in land use (Wang et al. 2018). ...
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As a form of green infrastructure, green roofs can enhance urban biodiversity by providing complex vegetation structures, supplying increased foraging and roosting opportunities for animals and increasing habitat connectivity. Although it is widely believed that green roofs can promote urban biodiversity, this idea has not been widely studied on an empirical scale. Therefore, a systematic understanding of the relationship between green roofs and biodiversity from different perspectives is still lacking. Here we provide a systematic review of the empirical literature on the relationship between green roofs and biodiversity. The results suggest that green roofs benefit urban biodiversity to some extent but cannot replace quondam natural habitats or complex artificial greening environments. Additionally, the studies reviewed here focused primarily on the diversity of plants or arthropods and were conducted almost exclusively in the United States and the United Kingdom. Moreover, most studies investigating the factors of green roofs affecting biodiversity focused on roof area, height, age, substrate depth, and plant community. To improve our understanding of the relationship between green roofs and urban biodiversity, more extensive research, particularly in developing countries, as well as more in-depth studies of a greater number of species and taxa, including chordates, mollusks and microbes, from different perspectives (e.g. at the genetic level) and other potential pathways are needed. In the future, the density, distribution pattern, distance and location relationship between different green roofs should be considered in an integrated manner. In order to more effectively support urban biodiversity, green roofs should be used in conjunction with other urban green spaces.
... As the human population and the proportion of urban areas both increase, there is a growing need for wildlife research that focuses on species interactions within a built-up landscape (DeStefano and DeGraaf 2003;Garden et al. 2006;Soulsbury and White 2015). An improved understanding of the ecology of urban wildlife is needed to inform management of the impacts of urbanisation on wildlife (Garden et al. 2006;Brearley 2012;Isaac et al. 2013;Stokeld et al. 2014;Weaving et al. 2014;FitzGibbon 2015) and to guide planning policies. There is a growing body of literature globally that indicates that tracking the movements of wildlife in urban environments can improve our understanding of urban wildlife ecology by providing insights into habitat utilisation and movement pathways (Grinder 2001;Lopez et al. 2004;Ordeñana et al. 2010;Poessel et al. 2014;Potapov et al. 2014;Weaving et al. 2014;Lewis et al. 2015). ...
Article
Context: As urban landscapes proliferate globally, the need for research into urban wildlife interactions is magnified. The eastern grey kangaroo (Macropus giganteus) is a widespread species commonly involved in wildlife-vehicle collisions in urban areas in Australia. Despite the many urban kangaroo populations and associated conflicts with human activities, few studies have examined how eastern grey kangaroos interact with, and are affected by, the urban matrix. Aims: The present study aimed to quantify kangaroo demography, movements, habitat utilisation and exposure to risks during a period of intensive urban development in a rapidly changing suburb located in a region undergoing high urban growth rates. Methods: We utilised foot-based census surveys, global positioning system (GPS) collars, direct observations and reports of wildlife mortality between 2014 and 2016. Geographical information systems (GIS) were used to integrate GPS-tracking data with spatial layers, to quantify kangaroo movements and habitat utilisation. Key results: The kangaroo population underwent a steep decline and kangaroo-vehicle collisions were the main source of mortality (73%) during the study period. Kangaroos were regularly exposed to the risk of injury, with roads intersecting many parts of their home range. Kangaroos showed positive habitat selection both for lawn and forest habitats and kangaroo movement and presence at the study site were influenced by high-quality forage and cover. Conclusions: The present research has highlighted that despite areas of suitable habitat remaining, road-kill was a major contributor to localised kangaroo-population decline. We showed that habitat preferences of eastern grey kangaroos in this urban area were consistent with those in natural landscapes. Implications: The present study is the first to implicate kangaroo-vehicle collisions as the major factor in population decline in kangaroos. These findings can be utilised to guide design and placement of kangaroo-vehicle collision mitigation and assist in planning of urban areas, particularly where kangaroo populations are in decline. Local extirpation of urban kangaroo populations would be greatly reduced by incorporating site-specific kangaroo habitat preferences and existing patterns of kangaroo habitat use in infrastructure planning. The study has contributed to our understanding of the effects of roads on urban wildlife in general and highlighted the importance of landscape permeability.
... To understand what factors influence powerful owl roost site selection across the broader landscape we used environmental variables considered important in previous studies (Table 1). We quantified roost locations in relation to three river types, road density, Normalised Difference Vegetation Index (NDVI) -a measure of vegetation productivity, parks, land use and tree cover (Bradsworth et al., 2017;Carter et al., 2019;Isaac et al., 2013;Isaac et al., 2014). We measured the Euclidian distance of roosts to primary, ephemeral, and man-made rivers across the study site. ...
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Increased urbanisation is placing respite areas for wildlife under stress, with the impact of anthropogenic disturbances such as noise, artificial light and infrastructure compounding as urban areas expand and become more populated. One essential, and sometimes overlooked behavioural activity is where urban wildlife sleep or rest. This is especially important for urban predators that are wide-ranging and exhibit specific ecological requirements. The powerful owl (Ninox strenua) is one such species. To ensure the future survival of urban powerful owls it is critical that we understand where they choose to roost/sleep and why. To determine these roosting characteristics, we used roosting data collected from GPS tagged powerful owls across Melbourne, Australia and examined these data at different spatial scales to provide a holistic understanding of habitat selection. At the landscape scale, potentially suitable roosting habitat was restricted heavily by urban and agricultural land use. Population-wide, roosts were located within dense tree cover with some flexibility between individuals in distance to river systems and tolerance of road density. At the microhabitat-scale, individual owls displayed flexibility by roosting in a variety of indigenous, non-indigenous native and exotic tree species. These considerations will assist urban planners to conserve suitable roosting habitat, while restoration efforts should be prioritised on private land and along river systems where roosting habitat can be enhanced and expanded, increasing landscape connectivity for other wildlife.
... In Powerful Owls, one model suggested that high prey abundance in urban woodland fragments could create an ecological trap if prey availability serves as cue to preferentially establish territories in areas without adequate nesting hollows 130(Isaac et al., 2014a). This followed on from a previous model that predicted declining habitat suitability with urbanization in Powerful Owls(Isaac et al. 2013). One study of nightbird occurrence in southeastern Australia, found differing impacts of fragmentation on occurrence of several owl species(Kavanagh and Stanton, 2002). ...
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The effects of habitat fragmentation on native wildlife can vary depending on the type of land use occurring in the matrix between remaining habitat fragments. I used Australian boobooks (Ninox boobook) in Western Australia to investigate interactions between matrix type and four different potential threatening processes: secondary poisoning by anticoagulant rodenticides (ARs); limitation of juvenile dispersal and impacts on spatial genetic structure; breeding site availability; and infection by the parasite Toxoplasma gondii. I also conducted a literature review on the use and regulation of ARs in Australia and published accounts of non-target impacts in order to contextualise exposure patterns observed in boobooks. The review revealed records of confirmed or suspected poisoning across 37 vertebrate species in Australia. World literature relating to AR exposure in reptiles suggests that they may be less susceptible to AR poisoning than birds and mammals. This relative resistance may create unevaluated risks for wildlife and humans in Australia where reptiles are more abundant than in cooler regions where AR exposure has been studied in greater depth. I analysed AR residues in boobook livers across multiple habitat types. Second generation anticoagulant rodenticides were detected in 72.6% of individuals sampled. Total AR concentration correlated positively with the proportion of urban land use within an area approximately the size of a boobook’s home range centred on the point where the sample was collected. ARs originating in urban habitat probably pose a substantial threat to boobooks and other predatory wildlife species. No spatial genetic structure was evident in boobooks across habitat types. I observed one individual dispersing at least 26km from its natal home range across urban habitat. The apparent permeability of anthropogenically altered landscapes probably explains the lack of spatial genetic structure and is likely related to the observed ability of boobooks to use resources in both urban and agricultural matrices. Boobooks did not appear to be limited by the availability of suitable nesting sites in urban or agricultural landscapes. Occupancy did not change significantly over the duration of the study in remnants provided with artificial nest boxes in either landscape type. However, in one instance, boobooks successfully used a nest box located in an urban bushland. Nest boxes may be a useful management tool in highly-altered areas where natural hollows are unavailable. Toxoplasma gondii seropositivity in boobooks did not vary significantly by landscape type but was more prevalent in individuals sampled during cooler wetter times of year. Risk of exposure due to greater cat abundance in urban and agricultural landscapes may be offset by creation of environmental conditions less favourable to the survival of T. gondii oocysts in soil. Taken together, this body of research demonstrates variation in relationships between different types of habitat fragmentation and threatening processes related to fragmentation. This research also raises questions about how habitat fragmentation is discussed and studied in the context of species which are capable of making extensive use of matrix habitat. I recommend greater consideration of the concept of “usable space” when studying fragmentation impacts in habitat generalists.
... molt 26 , migration 27 , hibernation 28 , breeding 29,30 ) to maintain efficiency in the future 31,32 . However, while theoretical and experimental investigations of changing foraging behaviors [33][34][35][36] and field-based assessments of predator habitat selection 32,[37][38][39] are common, studies examining how energetic demands impact the foraging behaviors of wide-ranging natural populations at fine temporal and spatial scales are rare 40,41 . Because these populations are likely to encounter complex patterns of environmental heterogeneity, obtaining this information will improve our understanding of the degree to which optimal foraging theory can describe animal behavior in dynamic environments. ...
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Optimal foraging theory states that animals should maximize resource acquisition rates with respect to energy expenditure, which may involve alteration of strategies in response to changes in resource availability and energetic need. However, field-based studies of changes in foraging behavior at fine spatial and temporal scales are rare, particularly among species that feed on highly mobile prey across broad landscapes. To derive information on changes in foraging behavior of breeding brown pelicans (Pelecanus occidentalis) over time, we used GPS telemetry and distribution models of their dominant prey species to relate bird movements to changes in foraging habitat quality in the northern Gulf of Mexico. Over the course of each breeding season, pelican cohorts began by foraging in suboptimal habitats relative to the availability of high-quality patches, but exhibited a marked increase in foraging habitat quality over time that outpaced overall habitat improvement trends across the study site. These findings, which are consistent with adjustment of foraging patch use in response to increased energetic need, highlight the degree to which animal populations can optimize their foraging behaviors in the context of uncertain and dynamic resource availability, and provide an improved understanding of how landscape-level features can impact behavior.
... Traditionally regarded as an old growth forest 87 specialist, this species is known to occur in urban landscapes (e.g. Cooke et al. 2018), 88 however, their presence is restricted due to land clearance and increased impervious 89 surfaces ( Isaac et al. 2013;Isaac et al. 2014). Most research to date has focussed on 90 ecological aspects such as diet, breeding, home range and habitat use; however, their 91 extremely limited sexual dimorphism has precluded adequate assessments of population 92 demography. ...
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The ability to distinguish (in the field) the sex of wildlife that show limited sexual dimorphism is, at best, challenging but is nonetheless essential to ensure appropriate conservation strategies are implemented. We developed a technique using highly varied images, similar to those taken by amateur photographers, to accurately sex individual powerful owls (Ninox strenua) through the measurement of facial features. Powerful owls show extremely limited sexual dimorphism and have been almost impossible to sex without genetic analysis, however, we report a process that results in the unambiguous assignment of sex. Image selection was extremely important; images where the owl’s head and body faced towards the camera, in an alert posture, were selected. We derived five facial features (inter-nostril distance, inter-eye distance, head width, forehead height and facemask), all measured in pixels to account for variation in the resolution and the size of images. Ratios were then produced from these facial features enabling standardised metrics, which we tested with regard to the assignment of sex. Logistic regression analysis indicated that the ratio of head width to the inter-nostril distance was the key sexually diagnostic relationship, giving 100% accuracy in sex determination (assessed against known-sex birds). We also identified a sex-specific plumage character; where facemask feathers protrude beyond the profile of the contour feathers of the head, the bird was a female, whereas when these feathers did not protrude beyond the profile, the bird was a male. For powerful owls, simple image analysis reliably determines the sex of individuals and has potential as an extremely cost efficient approach, that can provide essential information on species dynamics such as sex ratios, social organization and behaviour. The use of photographic images is especially beneficial for species that are cryptic or are extremely difficult to capture. The quantification and analysis of images captured by amateurs enables a greater contribution of citizen scientists to conservation research.
... It has been shown to occupy remnant vegetation in urban environments, but requires tree hollows for nesting and will also regularly utilise them for roosting (Weaving et al. 2011). Powerful owls were selected because, although they display some tolerance to urbanisation, they require extensive tree cover, a prey base of arboreal marsupials and large tree hollows for breeding (Cooke et al. 2006;Isaac et al. 2013Isaac et al. , 2014bBradsworth et al. 2017). The eastern barn owl was chosen because there has been very little research on aspects other than diet on this species in Australia. ...
Article
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.
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From the 1960s onwards, the European wild boar population has grown and expanded dramatically, invading agricultural areas and causing increasing damage to croplands and economic losses. The problem is particularly weighty in protected areas, where hunting is forbidden. In these areas the main ways the problem is tackled is through shooting, compensation payments after claims and prevention using electric fences. The aim of this study, based on the case of Elba Island (Central Italy), was to apply a management model for wild boar populations in protected areas able to mitigate social and economic conflicts with farmers and hunters. We identified which types of crops and structures were sensitive to damage, and the months in which the events were concentrated. Leslie–Davis and Ricker models were used to estimate the wild boar population in every year. Population viability analyses (PVAs) were carried out to define the minimum control effort that can lead to a strong population decline. Finally, to identify the areas most at risk of damage, we built a predictive model, using an ensemble forecasting approach, averaging the prediction obtained following Resource Selection Probability Functions and the maximum entropy algorithm Maxent.
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Information from natural history collections (NHCs) about the diversity, taxonomy and historical distributions of species worldwide is becoming increasingly available over the Internet. In light of this relatively new and rapidly increasing resource, we critically review its utility and limitations for addressing a diverse array of applications. When integrated with spatial environmental data, NHC data can be used to study a broad range of topics, from aspects of ecological and evolutionary theory, to applications in conservation, agriculture and human health. There are challenges inherent to using NHC data, such as taxonomic inaccuracies and biases in the spatial coverage of data, which require consideration. Promising research frontiers include the integration of NHC data with information from comparative genomics and phylogenetics, and stronger connections between the environmental analysis of NHC data and experimental and field-based tests of hypotheses.
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The distribution of records for the seven species of owls that have been recorded in the Sydney region are presented. Records made during the past decade have been compared, where possible, with records made since the beginning of the twentieth century. Information is also presented on aspects of the ecology (diet, habitat, nest sites, roost sites, breeding success) of these species in the Sydney region. The Powerful Owl is widely distributed, albeit at very low population density, throughout the outer suburbs of the greater metropolitan area, particularly where these suburbs adjoin substantial areas of bushland and reserves. The Sooty Owl and the Masked Owl are restricted to a few such locations near Sydney, but both are more common in the wetter and the drier forests, respectively, of the Central Coast. The Barking Owl appears to be uncommon and of concern because this species is poorly conserved in national parks of the region and its habitat is threatened by continued clearing for agriculture and urban developments. The Grass Owl appears to be a rare vagrant to the Sydney region. The Southern Boobook and the Barn Owl may be common in the region, but their distribution and abundance appears to have been under-represented by official records. The status of all owls is imperfectly known within the most suburban parts of the Sydney metropolitan area and on surrounding semi-rural properties. Efforts are needed to encourage broadscale community participation in voluntary surveys for owls (and several of their main prey species) throughout residential areas. The conservation of owls in the Sydney region depends on the protection of extensive bushland areas from urban and rural development, especially the major forested gully systems which provide essential nesting, roosting and core foraging habitat for most species. The role of fire frequency and weed control in Sydney's urban bushland needs to be examined in terms of its impact on populations of the Common Ringtail Possum, and other important prey species of the owls.
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Urban development can alter species composition and diversity within an area through biotic homogenization, the introduction of exotic species, and localized extinctions of native species. In this study we examined the composition and diversity of small terrestrial mammals within nature reserves surrounded by urban landscapes and compared this with previous surveys of these reserves and nearby non-urban reserves with similar vegetative and geomorphological characteristics. A combination of live trapping and indirect detection techniques was employed in eight reserves in the Australian Capital Territory and surrounding New South Wales to determine current species composition. Compared with previous studies and the non-urban reserves, the urban reserves appear to have lost two-thirds of their native terrestrial small mammal species in the past 26 years. Exotic species were present in all urban reserves, but were only associated with areas characterized by human-induced disturbance in non-urban reserves. Possible causes of this disparity in native species diversity between urban and non-urban reserves are discussed.
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We conducted point counts of diurnal raptors on Boulder, Colorado, grasslands for three winters and summers, and compared results to landscape features of the count areas. Four wintering species were scarce on plots that included significant amounts of urban habitat, with a critical landscape threshold at about 5-7% urbanization: Bald Eagle (Haliaeetus leucocephalus), Ferruginous Hawk (Buteo regalis), Rough-legged Hawk (B. lagopus), and Prairie Falcon (Falco mexicanus). Counts of the first three species also were positively correlated with proximity of the count plots to the nearest colony of black-tailed prairie dogs (Cynomys ludovicianus). Two breeding species, the Red-tailed Hawk (B. jamaicensis) and Swainson's Hawk (B. swainsoni), were more abundant on plots dominated by lowland hayfields and tallgrass prairies, as opposed to upland mixed and shortgrass prairies. They, along with the ubiquitous American Kestrel (Falco sparverius), were not sensitive to the amounts of urbanization (up to 30%) that occurred in the landscapes sampled. Results of this study suggest that urban open space grasslands can support sizable populations of most diurnal raptors, as long as prey populations persist, but that some species are highly sensitive to landscape urbanization.
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The diet of a pair of Powerful Owls, successfully breeding in regrowth open forest and woodland at Mt. Coot-tha, Brisbane, was assessed over two consecutive years. Diet was examined by analysing pellets and prey remains found below roosts and identifying carcasses the birds were holding. Eight mammal, sixteen bird and two insect species were recorded as prey, ranging in weight from 1 kg to 2 g. Fruit-bats, Common Ringtail Possums and Scalybreasted Lorikeets were taken most frequently. The estimated biomass of the four prey groups consumed each year was fruit-bats (46% both years), Common Ringtail Possum (25% in 1989, 29% in 1990), other arboreal marsupial species (17% and 7%) and diurnal birds (12% and 18%). There was a significant difference in biomass among prey groups each year. The frequency and biomass of prey groups in the diet did not differ significantly between the two years. There was no significant variation in the frequency of prey groups taken during the first four stages of the breeding cycle (incubation to fledgling) each year. Predation on Black and Greyheaded Fruit-bats and Scaly-breasted Lorikeets, species that are normally nomadic blossom and fruit feeders, occurred during all stages of the breeding cycle. Predation on the Common Ringtail Possum (predominantly juveniles) took place in suburbs adjacent to the study site. Hunting was observed within parkland and along forest edges.
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FULL-TEXT OF THE WHOLE PAPER AVAILABLE AT: http://www.scribd.com/doc/73688921/Roberge-Angelstam-2004-UsefulnessOfUmbrellaSpConc ABSTRACT: In the face of limited funding, knowledge, and time for action, conservation efforts often rely on shortcuts for the maintenance of biodiversity. The umbrella species concept - proposed as a way to use species requirements as a basis for conservation planning-has recently received growing attention. We reviewed the literature to evaluate the concept's general usefulness. An umbrella species is defined as a species whose conservation is expected to confer protection to a large number of naturally co-occurring species. This concept has been proposed as a tool for determining the minimum size for conservation areas, selecting sites to be included in reserve networks, and setting minimum standards for the composition, structure, and processes of ecosystems. Among the species suggested as potential umbrellas, most are large mammals and birds, but invertebrates are increasingly being considered. Eighteen research papers, most of which were based on hypothetical reserves or conservation networks, have provided evaluations of umbrella species schemes. These show that single-species umbrellas cannot ensure the conservation of all co-occurring species because some species are inevitably limited by ecological factors that are not relevant to the umbrella species. Moreover, they provide evidence that umbrella species from a given higher taxon may not necessarily confer protection to assemblages from other taxa. On the other hand, multi-species strategies based on systematic selection procedures (e. g., the focal species approach) offer more compelling evidence of the usefulness of the concept. Evaluations of umbrella species schemes could be improved by including measures of population viability and data from many years, as well as by comparing the efficiency of the proposed scheme with alternative management strategies.
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Human development impacts the landscape by altering the size and shape of natural habitat patches, replacing natural vegetation with other types such as lawns and row crops, or introducing environmental stressors such as increased human activity and pollutants. We investigated the effects of human alterations to the landscape on the distribution of 3 mammalian carnivores (coyote [Canis latrans ], raccoon [Procyon lotor ], and red fox [Vulpes vulpes ]) along an urban-rural gradient in northern Illinois. Distribution of each species was assessed from occurrence at scent stations placed within or along the edges of 47 sites ≥ 4 ha, representing 7 different natural or anthropogenically altered habitats. We averaged presence or absence scores across several seasonal samples over a year, and used an outlying mean index analysis to compare them to environmental variables gathered for each site, including habitat and landscape metrics presumed to reflect varying degrees of anthropogenic influence across the urban-rural gradient. Coyotes used a variety of habitats within the rural part of the gradient. Red foxes were found in forest interiors or shrubland and old fields near forests where coyotes were least detected. Both canids were detected more often in areas of lower human densities but prey abundance was not a strong determinant of their occurrence. Overall occurrence along the gradient was highest for raccoons, which were positively associated with urban areas with relatively high residential land use.
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Although spatial scale is important for understanding ecological processes and guiding conservation planning, studies combining a range of scales are rare. Habitat suitability modelling has been used traditionally to study broad-scale patterns of species distribution but can also be applied to address conservation needs at finer scales. We studied the ability of presence-only species distribution modelling to predict patterns of habitat selection at broad and fine spatial scales for one of the rarest mammals in the UK, the grey long-eared bat (Plecotus austriacus). Models were constructed with Maxent using broad-scale distribution data from across the UK (excluding Northern Ireland) and fine-scale radio-tracking data from bats at one colony. Fine-scale model predictions were evaluated with radio-tracking locations from bats from a distant colony, and compared with results of traditional radio-tracking data analysis methods (compositional analysis of habitat selection). Broad-scale models indicated that winter temperature, summer precipitation and land cover were the most important variables limiting the distribution of the grey long-eared bat in the UK. Fine-scale models predicted that proximity to unimproved grasslands and distance to suburban areas determine foraging habitat suitability around maternity colonies, while compositional analysis also identified unimproved grasslands as the most preferred foraging habitat type. This strong association with unimproved lowland grasslands highlights the potential importance of changes in agricultural practices in the past century for wildlife conservation. Hence, multi-scale models offer an important tool for identifying conservation requirements at the fine landscape level that can guide national-level conservation management practices.
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Background/Question/Methods Maxent, one of the most commonly used methods for inferring species distributions and environmental tolerances from occurrence data, allows users to fit models of arbitrary complexity. Model complexity is typically constrained via a process known as L1 regularization, but at present little guidance is available for setting the appropriate level of regularization, and the effects of inappropriately complex or simple models are largely unknown. In this study, we demonstrate the use of information criterion approaches to setting regularization in Maxent, and compare models selected using information criteria to models selected using other criteria that are common in the literature. We evaluate model performance using occurrence data generated from a known “true” initial Maxent model, using several different metrics for model quality and transferability. Results/Conclusions We demonstrate that models that are inappropriately complex or inappropriately simple show reduced ability to infer habitat quality, reduced ability to infer the relative importance of variables in constraining species’ distributions, and reduced transferability to other time periods. We also measure the relative effectiveness of different model selection criteria, and demonstrate that information criteria may offer significant advantages over the AUC-based methods commonly used in the literature.
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I examined the distribution and abundance of bird species across an urban gradient, and concomitant changes in community structure, by censusing summer resident bird populations at six sites in Santa Clara County, California (all former oak woodlands). These sires represented a gradient of urban land use that ranged from relatively undisturbed to highly developed, and included a biological preserve, recreational area, golf course, residential neighborhood, office park, and business district. The composition of the bird community shifted from predominantly native species in the undisturbed area to invasive and exotic species in the business district. Species richness, Shannon diversity, and bird biomass peaked at moderately disturbed sites. One or more species reached maximal densities in each of the sites, and some species were restricted to a given site. The predevelopment bird species (assumed to be those found at the most undisturbed site) dropped out gradually as the sites became more urban. These patterns were significantly related to shifts in habitat structure that occurred along the gradient, as determined by canonical correspondence analysis (CCA) using the environmental variables of percent land covered by pavement, buildings, lawn, grasslands, and trees or shrubs. I compared each formal site to four additional sites with similar levels of development within a two-county area to verify that the bird communities at the formal study sites were representative of their land use category.
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Compared with an undisturbed climax beech-maple forest, urbanization was presumed to be responsible for decreasing bird species richness and diversity, increasing biomass and density, and favoring dominance by a few species. Foraging guilds shifted from forest insectivores that were canopy foliage gleaners or bark drillers to urban ground gleaners. Although urban foliage height diversity was like that of the forest, the urban area contained only one-third of the total percent vegetative cover. Compared to the forest, urban vegetative cover was: 1) significantly less in all but the middle layer; 2) replaced by man-made structures, ground cover and ornamental vegetation in the low and middle layers but dominated the high layer; and 3) highly discontinuous, existing as isolated strata. -from Authors
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Defines urbanisation as those areas with a population of >620 individuals km-2. Characteristic urban structure and the range of components are also described. Urbanisation is seen as presenting a complex environmental gradient. Landscape ecology is discussed. By studying urban gradients humans can be seen as integral and critical components of ecological systems. -S.J.Yates
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ABSTRCT.--The Powerful Owl (Ninox strenua) is Australia's largest owl and is considered of least concern nationally. Although a number of studies have reported on the ecology of Powerful Owls inhabiting forests, few have focused on these owls living in urban areas. We report on the characteristics of different roost trees used by Powerful Owls in a continuum of habitats from urban Melbourne to the more forested outskirts. Records of weather conditions and daily temperatures were also analyzed to deter- mine whether the owls were selecting particular roost trees for specific climatic conditions. We found that roost-tree height and perch height was highly correlated, with the owls always roosting in the top one-third of the tree, regardless of the tree height. As ambient temperature increased perch height decreased, and vice-versa, but owls always roosted in the top one-third of the roost tree. Powerful Owls did not simply move up and down the one tree, but moved to more suitable trees according to the weather conditions. Hence, the species requires a structurally heterogeneous habitat to provide roost trees for different temperatures. Furthermore, successful management of this species in the future will require the protection of structurally diverse vegetation.
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This study investigates the diet of six breeding pairs of powerful owls in the Yarra Valley Corridor in Victoria, Australia, and compares prey consumption with prey availability. The six sites represent a continuum of habitats, ranging from urban Melbourne, through the urban fringe interface to a more forested landscape. We found that powerful owls in the Yarra Valley Corridor are reliant almost exclusively on arboreal marsupial prey as their preferred diet, with 99% of their overall diet comprising four arboreal marsupial species. These four species (the common ringtail possum, common brushtail possum, sugar glider and greater glider) were also the most abundant species observed while spotlighting; however, their abundance varied along the continuum. There was a strong positive relationship with the presence of these species in the diet and their site-specific availability, indicating that the powerful owl is a generalist hunter, preying on the most available prey at a given site and in a given season. This study suggests that food resources are high in these disturbed urban fringe sites and it is unlikely that food availability in urban environments will limit the potential survival of urban powerful owls.
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The Powerful Owl Ninox strenua is Australia's largest owl, and is mainly found east of the Great Dividing Range on the mainland in tall-open forests. The species is considered rare, both nation- ally and in the State of Victoria; and threatened in the Greater Melbourne area. Recovery plans for the future conservation management of N. strenua are being prepared in 2 states. Historically, Powerful Owls have been thought to require large homes ranges (about 1000 ha per pair) in suitable old-growth forest, which provides nest hollows for the owls and their arbo- real marsupial prey. Recent research, however, has found N. strenua may be more numerous and breed more successfully in a wider range of habitats than previously believed. In particular, the birds have been found living in forests and woodlands within the greater metropolitan areas of cities. The most extreme case is where a nest tree has been found within 800m of urban settle- ment and 6km from the centre of Brisbane. In this paper we report on the diet, habitat use, and conservation management by a number of breeding pairs of owls in outer urban Melbourne. Study sites range from a relatively undisturbed rainforest habitat 80km from central Melbourne, through dry sclerophyll, eucalyptus-dominated open forest with some disturbance to a site 8km from central Melbourne in highly disturbed urban parkland. Diets of the families of owls were determined by analyzing remains in regurgitated pellets. The data confirm that arboreal marsupials constitute the major prey items, especially the Common Ringtail Possum Pseudocheirus peregrinus. There were differences in diets depending on the availability of prey species, which suggest a level of opportunism not previously suspected. Our study is also the first to confirm the owls capture adult Common Brushtail Possums Trichosurus vulpecula (15% of pellets containing the remains of this large opossum have bones of mature adults at 1 site) and thus take prey up to two and a half times their own weight. As well our data suggest Powerful Owls are not restricted to hollow-dwelling prey, as in some sites the marsupials rested during the day either in leafy nests called dreys (P. peregrinus) or in house roofs (T. vulpecula). In the most heavily disturbed sites, breeding success has been reduced, and we have evidence that in one particular year the young were eaten by one of the parents. This followed construc- tion of a bicycle track under the nest during the breeding season. Recommendations are made for the future conservation and habitat management of Powerful Owls in the Yarra Valley corridor. Abstract
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The scent-station survey method has been widely used to estimate trends in carnivore abundance. However, statistical properties of scent-station data are poorly understood, and the relation between scent-station indices and carnivore abundance has not been adequately evaluated. We assessed properties of scent-station indices by analyzing data collected in Minnesota during 1986-93. Visits to stations separated by <2 km were correlated for all species because individual carnivores sometimes visited several stations in succession. Thus, visits to stations had an intractable statistical distribution. Dichotomizing results for lines of 10 stations (0 or ≥1 visits) produced binomially distributed data that were robust to multiple visits by individuals. We abandoned 2-way comparisons among years in favor of tests for population trend, which are less susceptible to bias, and analyzed results separately for biogeographic sections of Minnesota because trends differed among sections. Before drawing inferences about carnivore population trends, we reevaluated published validation experiments. Results implicated low statistical power and confounding as possible explanations for equivocal or conflicting results of validation efforts. Long-term trends in visitation rates probably reflect real changes in populations, but poor spatial and temporal resolution, susceptibility to confounding, and low statistical power limit the usefulness of this survey method.
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Anthropogenic land transformation processes in the vicinity of the Walter Sisulu National Botanical Garden, Johannesburg, South Africa, are a significant threat to natural vegetation and biodiversity. Breeding and feeding records of a Verreauxs' eagle (Aquila verreauxii),pair in the garden were analysed in relation to changes in the local environment due to urbanization. Natural prey-suitable habitat within a 10 km radius of the nest diminished by approximately 29.7 km2 (9.5%) during 1984–2007. In 2007 approximately 116.7 km2 (37.2%) of suitable prey habitat remained within this radius. Feeding data within a more recent period (1996–2008) suggest that there has been a switch from an optimal diet of rock hyrax (Procavia capensis)to less characteristic avian prey species such as helmeted guineafowl (Numida meleagris),francolins (Francolinus spp.) and supplemented food. Annual breeding success indicated few inconsistencies in incubation period, nestling period and postfledging dispersal period relative to breeding Verreauxs' eagle elsewhere. Despite a reduction in the suitable prey habitat and change in prey composition (including supplemental feeding), breeding has persisted successfully over a 16-year period (1993–2008). The presence of a large apex avian predator in an extensively urbanized metropolis is encouraging with regard to ecological integrity and functioning but the future prospects for these Verreauxs' eagles may depend on an as yet unknown threshold of prey abundance, both natural and supplemented, and environmental disturbance.
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The problem in biodiversity monitoring and conservation is that usually exist vast gaps in available information on the spatial distribution of biodiversity that poses a major challenge for the development of biodiversity indicators and regional conservation planning. Within this context, models that establish relationships between environmental variables and species occurrence have been developed to predict species distribution over large areas. We present an example using two indicator bird species, Tengmalm owl (Aegolius funereus) and Pygmy owl (Glaucidium passerinum). Maximum entropy (Maxent), a presence-only modelling approach, is used to model the distribution of these two species within a large study area in the French Alps. Despite biased sampling design, this method performs very well in predicting spatial distribution of the two owl species and brings useful information to help decision-making concerning the protection of valuable habitats.
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Abstract A Geographic Information System (GIS)-based model, using presence-only data, was used to predict suitability of habitat for large grazing ungulates on a Zimbabwean wildlife reserve. The management-driven study focused on rare and economically valuable herbivores during the resource-limited hot-dry season. The modelling software Biomapper was used to quantify species–habitat association and derive habitat suitability (HS) maps. Herbivore distribution was primarily determined by distance to surface water, time since last burn and herbaceous layer composition. Findings are discussed within the context of tools available to management and are used to address concerns about the potential for interspecific competition at the habitat level, stocking rate estimation and proposed infrastructure development. Biomapper allowed for the derivation of HS maps here despite the authors’ little modelling experience, and appears well suited to management-driven research of African fauna where access to GIS software is available.
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We present software that facilitates quantitative comparisons of environmental niche models (ENMs). Our software quantifies similarity of ENMs generated using the program Maxent and uses randomization tests to compare observed similarity to that expected under different null hypotheses. ENMTools is available online free of charge from <http://purl.oclc.org/enmtools>.
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When large carnivores are extirpated from ecosystems that evolved with apex predators, these systems can change at the herbivore and plant trophic levels. Such changes across trophic levels are called cascading effects and they are very important to conservation. Studies on the effects of reintroduced wolves in Yellowstone National Park have examined the interaction pathway of wolves (Canis lupus L., 1758) to ungulates to plants. This study examines the interaction effects of wolves to coyotes to rodents (reversing mesopredator release in the absence of wolves). Coyotes (Canis latrans Say, 1823) generally avoided areas near a wolf den. However, when in the proximity of a den, they used woody habitats (pine or sage) compared with herbaceous habitats (grass or forb or sedge)- when they were away from the wolf den. Our data suggested a significant increase in rodent numbers, particularly voles (genus Microtus Schrank, 1798), during the 3-year study on plots that were within 3 km of the wolf den, but we did not detect a significant change in rodent numbers over time for more distant plots. Predation by coyotes may have depressed numbers of small mammals in areas away from the wolf den. These factors indicate a top-down effect by wolves on coyotes and subsequently on the rodents of the area. Restoration of wolves could be a powerful tool for regulating predation at lower trophic levels.
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The exotic and native birds in the eastern suburbs of Melbourne, including the campus of Monash University, were studied during 1974-77. The proportion of exotic to native birds was far greater in suburban than native habitats. 'Total native vegetation' was found to be the most influential factor governing the number of both native and exotic birds, showing a positive and a negative correlation respectively. 'Total exotic plants' and various vegetation heights were also correlated, but were less important. The ground was the major foraging site for birds as a whole, followed by Eucalyptus spp. Native birds foraged proportionately more than did exotic birds on native rather than exotic plants, and in trees or shrubs rather than on the ground. When not foraging, they were seen proportionately more often than the exotics on native rather than exotic plants, and the exotics were seen proportionately far more often than the natives on artificial structures.
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Between 2004 and 2008 the diet and breeding success of a pair of Powerful Owls Ninox strenua were studied near Lakes Entrance, Victoria. In early November 2006 the adult female Powerful Owl was captured and radio-tracked for a period of 7.5 months. During this time the Owl's location was recorded on 111 occasions, including 65 nocturnal locations over 29 nights. Her home-range was calculated as 1589 ha using the Minimum Convex Polygon (MCP) method, or 871 ha based on the 95% Adaptive Kernel method. The area of forested habitat within the MCP home-range was 896 ha (the remainder representing cleared land). Her activity was centred primarily on the nesting gully where two dependent juveniles roosted, but several long-distance foraging expeditions (including roosting) that occurred more than 2.5 km from the juveniles were recorded. Arboreal mammals and birds dominated the Owls' diet. Low prey availability is suggested as being responsible for the single successful breeding event recorded in four nesting seasons.
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Aim Urbanization is a major driver of global land-use change, substantially modifying patterns of biodiversity. Managing these impacts has become a conservation priority. The creation and maintenance of greenways, such as river corridors, is frequently promoted as a strategy for mitigating habitat fragmentation in urban areas by bringing semi-natural habitat cover into city centres. However, there is little evidence to support this assertion. Here, we examine whether riparian zones maintain semi-natural habitat cover in urban areas and how species richness varies along such zones.
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With the rise of new powerful statistical techniques and GIS tools, the development of predictive habitat distribution models has rapidly increased in ecology. Such models are static and probabilistic in nature, since they statistically relate the geographical distribution of species or communities to their present environment. A wide array of models has been developed to cover aspects as diverse as biogeography, conservation biology, climate change research, and habitat or species management. In this paper, we present a review of predictive habitat distribution modeling. The variety of statistical techniques used is growing. Ordinary multiple regression and its generalized form (GLM) are very popular and are often used for modeling species distributions. Other methods include neural networks, ordination and classification methods, Bayesian models, locally weighted approaches (e.g. GAM), environmental envelopes or even combinations of these models. The selection of an appropriate method should not depend solely on statistical considerations. Some models are better suited to reflect theoretical findings on the shape and nature of the species’ response (or realized niche). Conceptual considerations include e.g. the trade-off between optimizing accuracy versus optimizing generality. In the field of static distribution modeling, the latter is mostly related to selecting appropriate predictor variables and to designing an appropriate procedure for model selection. New methods, including threshold-independent measures (e.g. receiver operating characteristic (ROC)-plots) and resampling techniques (e.g. bootstrap, cross-validation) have been introduced in ecology for testing the accuracy of predictive models. The choice of an evaluation measure should be driven primarily by the goals of the study. This may possibly lead to the attribution of different weights to the various types of prediction errors (e.g. omission, commission or confusion). Testing the model in a wider range of situations (in space and time) will permit one to define the range of applications for which the model predictions are suitable. In turn, the qualification of the model depends primarily on the goals of the study that define the qualification criteria and on the usability of the model, rather than on statistics alone.
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Urban development can have multiple effects on mammalian carnivore communities. We conducted a metaanalysis of 7,929 photographs from 217 localities in 11 camera-trap studies across coastal southern California to describe habitat use and determine the effects of urban proximity (distance to urban edge) and intensity (percentage of area urbanized) on carnivore occurrence and species richness in natural habitats close to the urban boundary. Coyotes (Canis latrans) and bobcats (Lynx rufus) were distributed widely across the region. Domestic dogs (Canis lupus familiaris), striped skunks (Mephitis mephitis), raccoons (Procyon lotor), gray foxes (Urocyon cinereoargenteus), mountain lions (Puma concolor), and Virginia opossums (Didelphis virginiana) were detected less frequently, and long-tailed weasels (Mustela frenata), American badgers (Taxidea taxus), western spotted skunks (Spilogale gracilis), and domestic cats (Felis catus) were detected rarely. Habitat use generally reflected availability for most species. Coyote and raccoon occurrence increased with both proximity to and intensity of urbanization, whereas bobcat, gray fox, and mountain lion occurrence decreased with urban proximity and intensity. Domestic dogs and Virginia opossums exhibited positive and weak negative relationships, respectively, with urban intensity but were unaffected by urban proximity. Striped skunk occurrence increased with urban proximity but decreased with urban intensity. Native species richness was negatively associated with urban intensity but not urban proximity, probably because of the stronger negative response of individual species to urban intensity.
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Habitat models are now broadly used in conservation planning on public lands. If implemented correctly, habitat modelling is a transparent and repeatable technique for describing and mapping biodiversity values, and its application in peri-urban and agricultural landscape planning is likely to expand rapidly. Conservation planning in such landscapes must be robust to the scrutiny that arises when biodiversity constraints are placed on developers and private landholders. A standardized modelling and model evaluation method based on widely accepted techniques will improve the robustness of conservation plans. We review current habitat modelling and model evaluation methods and provide a habitat modelling case study in the New South Wales central coast region that we hope will serve as a methodological template for conservation planners. We make recommendations on modelling methods that are appropriate when presence-absence and presence-only survey data are available and provide methodological details and a website with data and training material for modellers. Our aim is to provide practical guidelines that preserve methodological rigour and result in defendable habitat models and maps. The case study was undertaken in a rapidly developing area with substantial biodiversity values under urbanization pressure. Habitat maps for seven priority fauna species were developed using logistic regression models of species-habitat relationships and a bootstrapping methodology was used to evaluate model predictions. The modelled species were the koala, tiger quoll, squirrel glider, yellow-bellied glider, masked owl, powerful owl and sooty owl. Models ranked sites adequately in terms of habitat suitability and provided predictions of sufficient reliability for the purpose of identifying preliminary conservation priority areas. However, they are subject to multiple uncertainties and should not be viewed as a completely accurate representation of the distribution of species habitat. We recommend the use of model prediction in an adaptive framework whereby models are iteratively updated and refined as new data become available.
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Since European settlement of Australia, the dry open forests and woodlands of central Victoria have been extensively cleared and most large trees harvested, resulting in a decline of arboreal mammal populations. The Powerful Owl, which was formerly reliant on these prey species, still persists in the region but at very low densities and uncertain viability. Previous research has shown that Powerful Owls select home-ranges with more large trees and hollows than the forest at large, but the amount of such habitat that is required remained undefined. Four adult Powerful Owls (two males and two females) from four pairs occupying geographically separate territories in box-ironbark forest were radio-tracked over 1-6 months. Home-range size was much greater than previously assumed for this species (minimum convex polygon of 4774, 2896, 1770 and 1382 ha). Range-length was 5.7-8.9 km, and on average 5-12% of each home-range was used during a single night. Core foraging areas comprised many, typically small, patches scattered across the entire home-range. Selection of roosting sites was flexible and did not constrain spatial use of home-range, with 96% of roosts in very small to medium-sized trees, which are widely distributed. The finding of unexpectedly large foraging ranges suggests that enhancement of habitat quality and mammalian prey abundance in currently occupied home-ranges is the foremost goal for forest managers if a viable population is to be sustained.
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Variation in bird assemblages associated with forest clearing and urbanisation in the greater Brisbane area was assessed by counting birds in sites within six habitat categories: large remnants, small remnants, no- understorey remnants, canopy suburbs (original trees present), planted suburbs, and bare suburbs. Total bird abundance and species richness were generally highest in canopy suburbs. Individual species showed many significant abundance differences among the habitat types, and were classified into three major response categories: bushland species (3 in summer, 13 in winter), tolerant species (13 in summer, 13 in winter), and suburban species (12 in summer, 11 in winter). The commonly proposed notion that urbanisation results in lowered bird species richness and increases in introduced species is broadly consistent with the observed differences between bare suburbs and large remnants. However, it does not adequately describe the situation in the planted and canopy suburbs, where there was high species richness and extremely high abundance of some native species (including noisy miners, lorikeets, friarbirds, and butcherbirds) but low abundance of a majority of the species common in the original habitats (including fantails, wrens, whistlers, and other small insectivores). Retained forest remnants are essential for the latter group. Urban plantings of prolifically flowering native species do not reverse the effects of deforestation, but promote a distinctive group of common native suburban bird species. Origins of the urban bird assemblage are discussed.
Article
We studied the species richness and distribution of the forest raptor community in a New Jersey watershed in relation to urbanization. Raptors were systematically surveyed using high volume broadcasts of conspecific and heterospecific calls during the breeding season at a total of 81 survey stations. Ten habitat variables relevant to urbanization were measured at each survey station using to- pographic maps and aerial photographs. Results showed a community composed of 10 species of breed- ing raptors. Buteo lineatus, Accipiter gentilis and Strix varia showed a significant avoidance of suburban habitat, whereas B. jamaicensis and Bubo virginianus had a greater tendency to occupy such areas. Lowland habitat was significantly selected by S. varia, B. lineatus and A. cooper/i, a habitat usually most susceptible to development in the study region. Raptor species richness showed a strong positive correlation (r = 0.79, P < 0.01) with wilderness area size. No wilderness area less than 1000 ha had more than four raptor species while four to eight species were found in areas from 1000-8000 ha. Utilization of three
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In 1995, birds were surveyed in riparian woodlands along a gradient of urbanization in the Santa Clara Valley, CA, USA, in order to determine the relationships between riparian bird communities and urbanization. Bird species richness and density decreased at a location as the number of bridges near that location increased and as the volume of native vegetation decreased. Species richness also increased as the distance to the nearest building and the width of the riparian habitat increased. Canonical correspondence analysis confirmed that bird community structure was influenced strongly by these variables. Many individual species responded significantly to variables associated with urbanization, most having lower densities on more urbanized sites. Whereas previous studies have demonstrated substantial effects of urbanization on bird communities in the habitats being directly altered, this study indicates that urbanization on lands adjacent to intact riparian woodlands has substantial impacts on riparian bird communities.
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Coyotes (Canis latrans) are now ubiquitous throughout most of the eastern United States; however, little information exists on how they are able to exploit and thrive in fragmented landscapes. We investigated home ranges, movements, and scale-dependent resource selection of coyotes along a gradient (suburban/exurban/rural) of anthropogenic disturbance. Home-range sizes varied along a suburban-to-rural gradient and were inversely correlated to urbanization (R2 = 0.79, P < 0.001). Habitat composition and coyote use of 95% (home range) and 50% (core area) contours were nonrandom. Coyotes used corridor habitat extensively and avoided urban and crop-field habitats. Forested habitat was used extensively for diurnal cover. Rural coyotes traveled greater distances at faster rates than did suburban/exurban coyotes. Diel activity patterns were similar along the gradient, suggesting that coyotes responded similarly to differing levels and types of human activity. Coyotes appeared to assess habitat quality at the landscape scale and exploited small, disjunct resource patches present in developed landscapes. We believe that the availability of foraging habitat and travel corridors is critical to movement of coyotes in areas of high human activity.
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Varios aspectos de la ecología de los coyotes (Canis latrans) han sido estudiados en las ciudades (por ejemplo, su dieta, uso y selección del hábitat, movimientos), sin embargo información adicional puede ayudar a las personas responsables del manejo de depredadores urbanos. Estudiamos a los coyotes en el área central de Tucson, condado de Pima, Arizona, desde noviembre del 2005 hasta noviembre del 2006. Nuestro objetivo fue monitorear coyotes con radio-collares para determinar el tamaño del rango del hogar, para confirmar el uso del hábitat basado en categorías de uso de tierra y movimientos, y para describir una guarida de coyotes urbanos. El tamaño promedio del rango del hogar estimado para coyotes residentes, usando el método de fixed-kernel al 95%, fue 26.8 ± 5.1 ES km2. En general, las áreas mayormente seleccionadas fueron los arroyos secos y las áreas residenciales con densidad poblacional media y baja. Los movimientos fueron <520 m/h en las áreas que los coyotes utilizaron mayormente durante el día y la noche (por ejemplo las áreas de densidad residencial media y los arroyos secos) y >800 m/h en áreas que fueron usadas más durante la noche (por ejemplo áreas de alta densidad residencial y comercial). Los coyotes fueron capaces de suplir sus requisitos de vida en el centro de Tucson probablemente debido a los recursos disponibles y a la diversidad de categorías del uso de tierra, especialmente los arroyos secos.
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Adaptive and science-based management is widely accepted as necessary to safeguard wildlife and their habitats into the future. However, many of the decisions in this field are still based on unsupported ideas that lack validation with real data and which do not make their analysis available for a public review. Decisions based on soft foundations can be harmful to wildlife, habitat and the survival of both. I suggest a new wildlife management approach founded on scientific databases that has become possible, if not imperative, with improved technology and increasing access to freely available data over the Word Wide Web (WWW). This approach is partly a consequence of the effective implementation of the U.S. Freedom of Information Act and the National Spatial Data Infrastructure. In order to justify management decisions relating to wildlife, habitat, and conservation, the listing, use, and full investigation of all available and relevant databases needs to be implemented, voluntarily or legally, as a prerequisite. Second, similar to International Organization for Standardization (ISO) Standards, each major wildlife management decision needs to add a standard management documentation system as a backup that clearly records what data and research were or were not available at that time and what the recommended research still needs to address in order to complete the data situation and to decrease uncertainty.
Article
Aim The area under the receiver operating characteristic (ROC) curve (AUC) is a widely used statistic for assessing the discriminatory capacity of species distribution models. Here, I used simulated data to examine the interdependence of the AUC and classical discrimination measures (sensitivity and specificity) derived for the application of a threshold. I shall further exemplify with simulated data the implications of using the AUC to evaluate potential versus realized distribution models. Innovation After applying the threshold that makes sensitivity and specificity equal, a strong relationship between the AUC and these two measures was found. This result is corroborated with real data. On the other hand, the AUC penalizes the models that estimate potential distributions (the regions where the species could survive and reproduce due to the existence of suitable environmental conditions), and favours those that estimate realized distributions (the regions where the species actually lives). Main conclusions Firstly, the independence of the AUC from the threshold selection may be irrelevant in practice. This result also emphasizes the fact that the AUC assumes nothing about the relative costs of errors of omission and commission. However, in most real situations this premise may not be optimal. Measures derived from a contingency table for different cost ratio scenarios, together with the ROC curve, may be more informative than reporting just a single AUC value. Secondly, the AUC is only truly informative when there are true instances of absence available and the objective is the estimation of the realized distribution. When the potential distribution is the goal of the research, the AUC is not an appropriate performance measure because the weight of commission errors is much lower than that of omission errors.
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1. Biogeographical models of species' distributions are essential tools for assessing impacts of changing environmental conditions on natural communities and ecosystems. Practitioners need more reliable predictions to integrate into conservation planning (e.g. reserve design and management). 2. Most models still largely ignore or inappropriately take into account important features of species' distributions, such as spatial autocorrelation, dispersal and migration, biotic and environmental interactions. Whether distributions of natural communities or ecosystems are better modelled by assembling individual species' predictions in a bottom-up approach or modelled as collective entities is another important issue. An international workshop was organized to address these issues. 3. We discuss more specifically six issues in a methodological framework for generalized regression: (i) links with ecological theory; (ii) optimal use of existing data and artificially generated data; (iii) incorporating spatial context; (iv) integrating ecological and environmental interactions; (v) assessing prediction errors and uncertainties; and (vi) predicting distributions of communities or collective properties of biodiversity. 4. Synthesis and applications. Better predictions of the effects of impacts on biological communities and ecosystems can emerge only from more robust species' distribution models and better documentation of the uncertainty associated with these models. An improved understanding of causes of species' distributions, especially at their range limits, as well as of ecological assembly rules and ecosystem functioning, is necessary if further progress is to be made. A better collaborative effort between theoretical and functional ecologists, ecological modellers and statisticians is required to reach these goals.
Article
Summary 1. Conservation managers require accurate and timely information on the occurrence, size and viability of populations, but this is often difficult for cryptic species living at low densities over large areas. This study aimed to provide such information for tigers in the 36 400-km 2 Kerinci Seblat (KS) region, Sumatra, by identifying and assessing subpopu- lation viability under different management strategies. 2. Tiger occurrence was mapped within a geographical information system (GIS) using repeat detection-non-detection surveys to incorporate a function of detection probability into a logistic regression model. The landscape variables that influenced tiger occupancy were then used to construct a spatially explicit habitat model to identify core areas. 3. The number of tigers within each core area was estimated by calculating the area of different forest types and their respective tiger densities as determined through camera trapping. The viability of each subpopulation was then assessed under different management scenarios using a population viability analysis (PVA). 4. Tiger occurrence was negatively correlated with distance to public roads. Four core tiger areas were identified, all predominantly located within KS National Park, estimated to support subpopulations of 21, 105, 16 and three adult tigers, respectively. PVA showed that the three larger subpopulations could be demographically viable if well protected. However, if poaching removed ≥ 3 tigers per year, then only the largest subpopulation would not reach extinction within 50 years. Connectivity to this large subpopulation would ensure survival of the smaller subpopulations, through providing a source of tigers to offset poaching losses. 5. Synthesis and applications. Our key management recommendations for tigers in the Kerinci Seblat region of Sumatra stress the importance of maintaining connectivity between the smaller areas and the larger area, and minimizing poaching within these smaller areas. More widely, our research has shown the feasibility of using detection- non-detection surveys combined with spatial modelling to provide timely information for conservation management.
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