- Authors: Olson, Ashley
- Date: 2022
- Type: Text , Thesis , PhD
- Full Text: false
- Description: A fundamental goal of biogeography is to determine how communities of species assemble. Islands offer an excellent opportunity to study community assembly because they have discrete boundaries, their species compliment can be readily quantified, and biogeographic processes operating at broad spatial scales can be separated from the effects of local interactions. Indeed, islands have contributed extensively to the development of biogeographical theory. Historically, the focus of island biogeography studies has been to predict the species richness of their communities. Yet, species richness provides no information about the ecological differences among the species that comprise a community, and thus cannot explain why different types of species do, or do not, appear in island communities. The niche of any particular species represents all of the abiotic and interspecific interactions that determine the survival of that species in a given location. Thus, a niche-based description of island communities differs from a richness-only description as it can link biogeography to the ecological interactions that ultimately drive successful colonisation and evolution on an island. However, island isolation and island area - the key predictors of species immigration and extinction, respectively - and the influence of the composition of the regional species pool have rarely been investigated for their effect on niche differences among species occupying an island. Understanding how the regional species pool, isolation and area influence niche-based diversity on islands provides an important link between biogeography and the ecological interactions that ultimately determine the composition of island communities. I used data on the island birds across Melanesian archipelagos to explore the role of biogeography in driving the niche-based structure of island communities. Specifically, I studied how the composition of the regional species pool, island isolation and island area influence: i) variation in a key functional trait (body size), ii) occupancy and saturation of niches, and iii) the phylogenetic structure of island communities. To do so, I studied three Melanesian archipelagos; the Bismarck, Solomon and Vanuatu islands, each of which represent a separate biogeographic region with a different degree of isolation from the primary source of avian colonists, mainland New Guinea. As such, the influence of oceanic dispersal barriers on the composition of the avifauna of each archipelago can be clearly distinguished. Using this model system, I demonstrate that the effects of island isolation and island area extend beyond determining the number of species on an island to influencing maximum body size, niche occupancy and the phylogenetic structure of island communities. Further, the research I describe in this thesis demonstrates that the influence of island isolation and area on the ecological and evolutionary differences among species that comprise each island community is mediated by the diversity of the regional species pool. Thus, the species observed in island communities, and the niches they occupy, may not be a product of local ecological interactions. Rather, immigration from the regional species pool may determine the persistence of a species on an island.
- Description: Doctor of Philosophy
Investigating bird responses to fire in the Heathy Dry Forests of Victoria, Australia
- Authors: Kuchinke, Diana
- Date: 2018
- Type: Text , Thesis , PhD
- Full Text:
- Description: Globally, forest birds are under pressure, from agriculture and urban development fragmenting the landscape. Adding to these pressures, changes in the patterns of global climate drivers give rise to an increase in the frequency of extreme weather events. In Victoria, Australia, changing weather conditions are resulting in increases in the frequency and extent of bushfires. Furthermore, prescribed burning is applied to the landscape in attempts to not only ameliorate the impacts from bushfire, but as part of a ‘pyrodiversity begets biodiversity’ protocol. These pressures all impact birds by reducing resources for: food, nesting and protection from predators. This thesis investigated bird responses to fire in the Heathy Dry Forests of Victoria, against variables of time-since-fire and fire frequency. Bird responses were modelled in terms of: community, foraging guilds and individual species. As a community, birds showed a resilience to both time since fire and fire frequency. Responses by foraging guilds and individual species highlighted some different responses. The common species from each foraging guild showed responses that broadly represent their guild. This thesis highlighted that an effective tool in adaptive management is to predict the trends of our common forest birds, as surrogates for entire bird communities, not just for fire responses, but for a broader reflection on the health of the landscape. The modelling of one species, the Laughing Kookaburra, showed a response to both time since fire and fire frequency, with a reduced abundance in post-fire new-growth vegetation. As this species is noted as being in decline down the east coast of Australia, it is flagged in this thesis as a species of concern. Further, this thesis investigated alpha and beta responses by the forest birds to prescribed burns of different severities. Results suggest that forest birds show little response to small prescribed burns in the landscape, regardless of severity. This may be a result of Heathy Dry Forests’ rapid regeneration post-fire. However, one species that exhibits site fidelity, the White-throated Treecreeper, left areas impacted by high severity prescribed burns. The White-throated Treecreeper’s response flagged the importance of tree hollows being maintained in the landscape, essential for the species that require hollows for roosting and nesting.
- Description: Doctor of Philosophy
- Description: Globally, forest birds are under pressure, from agriculture and urban development fragmenting the landscape. Adding to these pressures, changes in the patterns of global climate drivers give rise to an increase in the frequency of extreme weather events. In Victoria, Australia, changing weather conditions are resulting in increases in the frequency and extent of bushfires. Furthermore, prescribed burning is applied to the landscape in attempts to not only ameliorate the impacts from bushfire, but as part of a ‘pyrodiversity begets biodiversity’ protocol. These pressures all impact birds by reducing resources for: food, nesting and protection from predators. This thesis investigated bird responses to fire in the Heathy Dry Forests of Victoria, against variables of time-since-fire and fire frequency. Bird responses were modelled in terms of: community, foraging guilds and individual species. As a community, birds showed a resilience to both time since fire and fire frequency. Responses by foraging guilds and individual species highlighted some different responses. The common species from each foraging guild showed responses that broadly represent their guild. This thesis highlighted that an effective tool in adaptive management is to predict the trends of our common forest birds, as surrogates for entire bird communities, not just for fire responses, but for a broader reflection on the health of the landscape. The modelling of one species, the Laughing Kookaburra, showed a response to both time since fire and fire frequency, with a reduced abundance in post-fire new-growth vegetation. As this species is noted as being in decline down the east coast of Australia, it is flagged in this thesis as a species of concern. Further, this thesis investigated alpha and beta responses by the forest birds to prescribed burns of different severities. Results suggest that forest birds show little response to small rescribed burns in the landscape, regardless of severity. This may be a result of Heathy Dry Forests’ rapid regeneration post-fire. However, one species that exhibits site fidelity, the White-throated Treecreeper, left areas impacted by high severity prescribed burns. The White-throated Treecreeper’s response flagged the importance of tree hollows being maintained in the landscape, essential for the species that require hollows for roosting and nesting.
- Authors: Kuchinke, Diana
- Date: 2018
- Type: Text , Thesis , PhD
- Full Text:
- Description: Globally, forest birds are under pressure, from agriculture and urban development fragmenting the landscape. Adding to these pressures, changes in the patterns of global climate drivers give rise to an increase in the frequency of extreme weather events. In Victoria, Australia, changing weather conditions are resulting in increases in the frequency and extent of bushfires. Furthermore, prescribed burning is applied to the landscape in attempts to not only ameliorate the impacts from bushfire, but as part of a ‘pyrodiversity begets biodiversity’ protocol. These pressures all impact birds by reducing resources for: food, nesting and protection from predators. This thesis investigated bird responses to fire in the Heathy Dry Forests of Victoria, against variables of time-since-fire and fire frequency. Bird responses were modelled in terms of: community, foraging guilds and individual species. As a community, birds showed a resilience to both time since fire and fire frequency. Responses by foraging guilds and individual species highlighted some different responses. The common species from each foraging guild showed responses that broadly represent their guild. This thesis highlighted that an effective tool in adaptive management is to predict the trends of our common forest birds, as surrogates for entire bird communities, not just for fire responses, but for a broader reflection on the health of the landscape. The modelling of one species, the Laughing Kookaburra, showed a response to both time since fire and fire frequency, with a reduced abundance in post-fire new-growth vegetation. As this species is noted as being in decline down the east coast of Australia, it is flagged in this thesis as a species of concern. Further, this thesis investigated alpha and beta responses by the forest birds to prescribed burns of different severities. Results suggest that forest birds show little response to small prescribed burns in the landscape, regardless of severity. This may be a result of Heathy Dry Forests’ rapid regeneration post-fire. However, one species that exhibits site fidelity, the White-throated Treecreeper, left areas impacted by high severity prescribed burns. The White-throated Treecreeper’s response flagged the importance of tree hollows being maintained in the landscape, essential for the species that require hollows for roosting and nesting.
- Description: Doctor of Philosophy
- Description: Globally, forest birds are under pressure, from agriculture and urban development fragmenting the landscape. Adding to these pressures, changes in the patterns of global climate drivers give rise to an increase in the frequency of extreme weather events. In Victoria, Australia, changing weather conditions are resulting in increases in the frequency and extent of bushfires. Furthermore, prescribed burning is applied to the landscape in attempts to not only ameliorate the impacts from bushfire, but as part of a ‘pyrodiversity begets biodiversity’ protocol. These pressures all impact birds by reducing resources for: food, nesting and protection from predators. This thesis investigated bird responses to fire in the Heathy Dry Forests of Victoria, against variables of time-since-fire and fire frequency. Bird responses were modelled in terms of: community, foraging guilds and individual species. As a community, birds showed a resilience to both time since fire and fire frequency. Responses by foraging guilds and individual species highlighted some different responses. The common species from each foraging guild showed responses that broadly represent their guild. This thesis highlighted that an effective tool in adaptive management is to predict the trends of our common forest birds, as surrogates for entire bird communities, not just for fire responses, but for a broader reflection on the health of the landscape. The modelling of one species, the Laughing Kookaburra, showed a response to both time since fire and fire frequency, with a reduced abundance in post-fire new-growth vegetation. As this species is noted as being in decline down the east coast of Australia, it is flagged in this thesis as a species of concern. Further, this thesis investigated alpha and beta responses by the forest birds to prescribed burns of different severities. Results suggest that forest birds show little response to small rescribed burns in the landscape, regardless of severity. This may be a result of Heathy Dry Forests’ rapid regeneration post-fire. However, one species that exhibits site fidelity, the White-throated Treecreeper, left areas impacted by high severity prescribed burns. The White-throated Treecreeper’s response flagged the importance of tree hollows being maintained in the landscape, essential for the species that require hollows for roosting and nesting.
Movements, Behaviour and Ecology of the Brolga, Antigone rubicunda, at multiple spatial and temporal scales
- Authors: Veltheim, Inka
- Type: Thesis , PhD
- Full Text:
- Description: The study of animal movement patterns, within and between habitats, is a key consideration in ecological and evolutionary disciplines. Movement studies address: where, when, why and how animals move and what scales are movements taken at? For example: when and how animals move in response to internal factors, such as the need to breed, or external factors such as weather? Understanding animal movements is crucial in conservation planning and management of species. My thesis aim was to understand brolga (Antigone rubicunda) spatial landscape use across their south-east Australian core range at multiple scales. The information presented in this thesis can be applied for conservation and management of the species. I deployed 23 GPS transmitters on adults (5), juveniles (6) and chicks (12) and used a range of modelling approaches, location data and behavioural data to study their movements. Modelling methods included: behavioural change point analysis, kernel density analysis and Brownian bridge movement models to estimate home ranges; Maxent to build a species distribution model, parametric compositional analysis to study habitat selection; Bayesian and frequentist linear models to investigate relationships between environmental variables and movements, habitat use and behaviour; and NicheMapperTM to understand ecophysiological drivers of movement behaviour. GPS-tracking revealed two seasonal movement strategies within the south-west Victorian brolga range with individuals moving either 100 km or 20 km on average, between non-breeding and breeding areas, depending on capture location. However, I found many exceptions to a strictly seasonal pattern of movement, suggesting brolgas have a flexible and adaptable movement strategy. Brolgas adopted a migratory or resident strategy, indicating that the south-west Victorian population is partially migratory. I investigated whether a dynamic species distribution model (dSDM), built with Maxent using short-term weather variables, could predict seasonal distribution and movements of brolgas at a landscape scale. Using GPS tracking data to validate the dSDM output, I demonstrated that the dSDM was useful for modelling occupancy and seasonal distribution, but did not explicitly capture movements at the scale the movements occurred. However, brolgas moved further and occupied highest suitable habitat available when predicted habitat suitability in south-west Victoria was low, suggesting brolgas track areas with high predicted habitat suitability. Dynamic species distribution models may be useful in identifying suitable habitat when overall habitat suitability within a species’ range is low. At the home range scale, I used the Brownian bridge movement model to estimate breeding home range size and parametric compositional analysis to determine habitat use and selection by brolgas. I expected wetland size, density and number of chicks in a clutch to influence home range sizes, however, found only weak evidence for greater home ranges with increased clutch size. Brolgas used either single or multiple wetlands within their home ranges, and those using multiple wetlands either switched between wetlands or relocated permanently. Within their breeding home ranges brolgas appeared to select against buildings and watercourses but showed no selection for land use type. At the daily scale, I focused on movement behaviour of brolgas between foraging areas in cropped paddocks and wetland roosts. I used a correlative and a mechanistic model to investigate the influence of thermoregulatory constraints and weather on daily movement decisions of brolgas. Movements between the two habitats were not driven by biophysical requirements. The results suggest brolgas tolerate a range of weather conditions before shifting habitats to reduce heat stress and metabolic costs or to maintain water balance. In this thesis, I discuss the ecological and conservation implications of my research findings. Finally, I also provide recommendations for avoiding wind farm impacts on the threatened south-west Victorian brolga population given my findings on daily, seasonal and annual movement patterns. Many studies have investigated wind farm impacts on birds. However, this is one of a few that considers all lifecycle stages, and takes a multi-site and -scale approach to studying bird movements to inform conservation and wind farm planning.
- Authors: Veltheim, Inka
- Type: Thesis , PhD
- Full Text:
- Description: The study of animal movement patterns, within and between habitats, is a key consideration in ecological and evolutionary disciplines. Movement studies address: where, when, why and how animals move and what scales are movements taken at? For example: when and how animals move in response to internal factors, such as the need to breed, or external factors such as weather? Understanding animal movements is crucial in conservation planning and management of species. My thesis aim was to understand brolga (Antigone rubicunda) spatial landscape use across their south-east Australian core range at multiple scales. The information presented in this thesis can be applied for conservation and management of the species. I deployed 23 GPS transmitters on adults (5), juveniles (6) and chicks (12) and used a range of modelling approaches, location data and behavioural data to study their movements. Modelling methods included: behavioural change point analysis, kernel density analysis and Brownian bridge movement models to estimate home ranges; Maxent to build a species distribution model, parametric compositional analysis to study habitat selection; Bayesian and frequentist linear models to investigate relationships between environmental variables and movements, habitat use and behaviour; and NicheMapperTM to understand ecophysiological drivers of movement behaviour. GPS-tracking revealed two seasonal movement strategies within the south-west Victorian brolga range with individuals moving either 100 km or 20 km on average, between non-breeding and breeding areas, depending on capture location. However, I found many exceptions to a strictly seasonal pattern of movement, suggesting brolgas have a flexible and adaptable movement strategy. Brolgas adopted a migratory or resident strategy, indicating that the south-west Victorian population is partially migratory. I investigated whether a dynamic species distribution model (dSDM), built with Maxent using short-term weather variables, could predict seasonal distribution and movements of brolgas at a landscape scale. Using GPS tracking data to validate the dSDM output, I demonstrated that the dSDM was useful for modelling occupancy and seasonal distribution, but did not explicitly capture movements at the scale the movements occurred. However, brolgas moved further and occupied highest suitable habitat available when predicted habitat suitability in south-west Victoria was low, suggesting brolgas track areas with high predicted habitat suitability. Dynamic species distribution models may be useful in identifying suitable habitat when overall habitat suitability within a species’ range is low. At the home range scale, I used the Brownian bridge movement model to estimate breeding home range size and parametric compositional analysis to determine habitat use and selection by brolgas. I expected wetland size, density and number of chicks in a clutch to influence home range sizes, however, found only weak evidence for greater home ranges with increased clutch size. Brolgas used either single or multiple wetlands within their home ranges, and those using multiple wetlands either switched between wetlands or relocated permanently. Within their breeding home ranges brolgas appeared to select against buildings and watercourses but showed no selection for land use type. At the daily scale, I focused on movement behaviour of brolgas between foraging areas in cropped paddocks and wetland roosts. I used a correlative and a mechanistic model to investigate the influence of thermoregulatory constraints and weather on daily movement decisions of brolgas. Movements between the two habitats were not driven by biophysical requirements. The results suggest brolgas tolerate a range of weather conditions before shifting habitats to reduce heat stress and metabolic costs or to maintain water balance. In this thesis, I discuss the ecological and conservation implications of my research findings. Finally, I also provide recommendations for avoiding wind farm impacts on the threatened south-west Victorian brolga population given my findings on daily, seasonal and annual movement patterns. Many studies have investigated wind farm impacts on birds. However, this is one of a few that considers all lifecycle stages, and takes a multi-site and -scale approach to studying bird movements to inform conservation and wind farm planning.
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