Tree-Encoded Bitmaps

We propose a novel method to represent compressed bitmaps. Similarly to existing bitmap compression schemes, we exploit the compression potential of bitmaps populated with consecutive identical bits, i.e., 0-runs and 1-runs. But in contrast to prior work, our approach employs a binary tree structure to represent runs of various lengths. Leaf nodes in the upper tree levels thereby represent longer runs, and vice versa. The tree-based representation results in high compression ratios and enables efficient random access, which in turn allows for the fast intersection of bitmaps. Our experimental analysis with randomly generated bitmaps shows that our approach significantly improves over state-of-the-art compression techniques when bitmaps are dense and/or only barely clustered. Further, we evaluate our approach with real-world data sets, showing that our tree-encoded bitmaps can save up to one third of the space over existing techniques

Movements, Behaviour and Ecology of the Brolga, <i>Antigone rubicunda</i>, at multiple spatial and temporal scales

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