Bronwyn Louise Isaac

Simplification of arboreal marsupial assemblages in response to increasing urbanization.

Arboreal marsupials play an essential role in ecosystem function including regulating insect and plant populations, facilitating pollen and seed dispersal and acting as a prey source for higher-order carnivores in Australian environments. Primarily, research has focused on their biology, ecology and response to disturbance in forested and urban environments. We used presence-only species distribution modelling to understand the relationship between occurrences of arboreal marsupials and eco-geographical variables, and to infer habitat suitability across an urban gradient. We used post-proportional analysis to determine whether increasing urbanization affected potential habitat for arboreal marsupials. The key eco-geographical variables that influenced disturbance intolerant species and those with moderate tolerance to disturbance were natural features such as tree cover and proximity to rivers and to riparian vegetation, whereas variables for disturbance tolerant species were anthropogenic-based (e.g., road density) but also included some natural characteristics such as proximity to riparian vegetation, elevation and tree cover. Arboreal marsupial diversity was subject to substantial change along the gradient, with potential habitat for disturbance-tolerant marsupials distributed across the complete gradient and potential habitat for less tolerant species being restricted to the natural portion of the gradient. This resulted in highly-urbanized environments being inhabited by a few generalist arboreal marsupial species. Increasing urbanization therefore leads to functional simplification of arboreal marsupial assemblages, thus impacting on the ecosystem services they provide.

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

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.

The distribution of three nocturnal bird species across a suburban-forest gradient

Abstract On a global scale, urbanisation has a profound effect on the distribution of wildlife. Here we seek to test the effects of urban encroachment on the distribution of three key members of the Australian nocturnal bird community: the Tawny Frogmouth (Podargus strigoides), Australian Owlet-nightjar (Aegotheles cristatus) and Southern Boobook (Ninox novaeseelandiae). The distribution of the species was recorded in three landscape types—suburban, urban-fringe and forest—with the level of urbanisation classified according to attributes at both landscape level and site level. The effects of urbanisation on individual species were determined by a comparison of broad landscape attributes and species distributions. Site-level attributes were modelled to determine their influence on the presence of species. Although all three species occurred in the urban-fringe landscape (50–64% of sites), the presence of the Tawny Frogmouth, a species with more generalist habitat requirements, increased in response to increasing levels of urbanisation. The Australian Owlet-nightjar and Southern Boobook, which have more specialised habitat requirements than the Frogmouth, showed a corresponding decrease in presence to increasing levels of urbanisation. Although all three species appear to tolerate the level of disturbance in urban-fringe environments, these areas are also at risk of further degradation. It is critical that continued research focuses on urban-fringe environments to investigate species-specific demographic responses to urban gradients.

Powerful Owls: Possum Assassins Move into Town

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

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

Abstract 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.

Urbanization and Raptors: Trends and Research Approaches

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.

New tools for a new age: An evolution or revolution in higher education?

In this paper we describe how digital technologies can be used to enhance collaboration and student engagement in a large, multicampus undergraduate science unit. Four innovations developed and implemented over a period of eight years are described: use of electronic whiteboards, on-line discussion forums, social media and blogs. In showing the intermediate steps in the evolution of the use of digital and communication technologies, we demonstrate that to be effective, good educational principles are paramount.