Solitary Vireos (Vireo solitarius alticola) were studied on an extensive mature forest landscape in 1994 and on three sites harvested using the group selection method in 1995. Pairing success was 88% on the unharvested site in 1994, however it was lower on the harvested sites in 1995 (53.8%). Low reproductive success was observed in both years (12% and 22% respectively). In 1995, the amount of opening within a 200 meter radius of the first observation point of a male was positively related to pairing success (p<0.05). This suggests that females may be cueing in on the increased number of shrubs in and around openings. / Master of Science

The recent development of multi-core computer architectures has largely affected the creation of everyday applications, requiring the adoption of concurrent programming to significantly utilize the divided processing power of computers. Applications must be split into sections able to execute in parallel, without any of these sections conflicting with one another, thereby necessitating some form of synchronization to be declared. The most commonly used methodology is lock-based synchronization; although, to improve performance the most, developers must typically form complex, low-level implementations for large applications, which can easily create potential errors or hindrances. An abstraction from database systems, known as transactions, is a rising concurrency control design aimed to circumvent the challenges with programmability, composability, and scalability in lock-based synchronization. Transactions execute their operations speculatively and are capable of being restarted (or rolled back) when there exist conflicts between concurrent actions. As such issues can occur later in the lifespans of transactions, entire rollbacks are not that effective for performance. One particular method, known as nesting, was created to counter that drawback. Nesting is the act of enclosing transactions within other transactions, essentially dividing the work into pieces called sub-transactions. These sub-transactions can roll back without affecting the entire main transaction, although general nesting models only allow one sub-transaction to perform work at a time. The first main contribution in this thesis is SPCN, an algorithm that parallelizes nested transactions while automatically processing any potential conflicts that may arise, eliminating the burden of additional processing from the application developers. Two versions of SPCN exist: Strict, which enforces the sub-transactions' work to be made visible in a serialized order; and Relaxed, which allows sub-transactions to distribute their information immediately as they finish (therefore invalidation may occur after-the-fact and must be handled). Despite the additional logic required by SPCN, it outperforms traditional closed nesting by 1.78x at the lowest and 3.78x at the highest in the experiments run. Another method to alter transactional execution and boost performance is to relax the rules of visibility for parallel operations (known as their isolation). Depending on the application, correctness is not broken even if some transactions see external work that may later be undone due to a rollback, or if an object is written while another transaction is using an older instance of its data. With lock-based synchronization, developers would have to explicitly design their application with varying amounts of locks, and different lock organizations or hierarchies, to change the strictness of the execution. With transactional systems, the processing performed by the system itself can be set to utilize different rulings, which can change the performance of an application without requiring it to be largely redesigned. This notion leads to the second contribution in this thesis: AsR, or As-Serializable transactions. Serializability is the general form of isolation or strictness for transactions in many applications. In terms of execution, its definition is equivalent to only one transaction running at a time in a given system. Many transactional systems use their own internal form of locking to create Serializable executions, but it is typically too strict for many applications. AsR transactions allow the internal processing to be relaxed while additional meta-data is used external to the system, without requiring any interaction from the developer or any changes to the given application. AsR transactions offer multiple orders of magnitude more in throughput in highly-contentious scenarios, due to their capability to outlast traditional levels of isolation. / Master of Science

In order to prevent species extinctions, conservation strategies need to incorporate the identification and mitigation of the root causes of population decline with an assessment of vulnerability to genetic and stochastic factors affecting small populations. Species or populations with small ranges, such as those on islands, are particularly vulnerable to extinction, and deficient knowledge of these species often impedes conservation efforts. The Bahama Swallow (Tachycineta cyaneoviridis) is an endangered secondary cavity-nester that only breeds on three islands in the northern Bahamas: Abaco, Grand Bahama, and Andros. I investigated questions related to population size and distribution, genetic diversity and population structure, breeding biology, and ecological interactions of the swallow, with the goal of informing the conservation and management of the species. Using several population survey methods on Abaco, I found that swallow site occupancy and density is higher in southern Abaco, especially near roads and pine snags. Future research should prioritize identifying the causes of variable and low population densities in parts of the swallow's range. I used microsatellite markers and morphometrics to assess differences between populations on Abaco and Andros. We found a lack of genetic differentiation (G'ST = 0.03) between populations, but differences in morphology suggest that gene flow might be low enough to enable traits under selection to diverge. By locating and monitoring nests, I found that swallows rely on woodpecker-excavated cavities in pine snags and utility poles, and that swallows nesting in pine snags had higher fledging success (92%) than those nesting in utility poles (50-62%). Using a cavity nest-web approach, I assessed how swallows interact with cavity-nesting birds and resources on Abaco. Hairy Woodpeckers (Dryobates villosus) primarily excavated pine snags, while West Indian Woodpeckers (Melanerpes superciliaris) excavated utility poles in non-pine habitat. Only swallows and La Sagra's Flycatchers (Myiarchus sagrae) used nest sites in the pine forest. Swallows in non-pine habitat face competition for cavities with American Kestrels (Falco sparverius), and non-native House Sparrows (Passer domesticus) and European Starlings (Sturnus vulgaris). These results highlight the importance of pine forest and the Hairy Woodpecker for the persistence of the swallow. / Doctor of Philosophy / In order to prevent species extinctions, conservation strategies need to identify and resolve the problems that cause species to decline, as well as address issues characteristic of small populations. Species or populations with small ranges, such as those on islands, are particularly vulnerable to extinction, and lack of knowledge of these species often impedes conservation efforts. The Bahama Swallow is an endangered species that only breeds on three "pine islands" in the northern Bahamas. The swallow is a secondary cavity-nester, which means that it nests in a cavity, usually either a natural tree hole or a hole created by another bird species. In this study, I investigated where swallows are found on the islands, the genetics and body sizes of populations, nesting biology, and connections with other species, with the goal of providing information for the conservation and management of the species. On Abaco, I found that there are more swallows in the southern part of the island, especially near roads and the dead standing pine trees (pine snags) used for nesting. Future research should assess why there are fewer birds in other parts of the swallow's range. I tested whether the genetics and body sizes of populations on Abaco and Andros are different from each other. Populations were genetically similar, but may be separated enough to result in body size differences. I located swallow nests on Abaco, and found that swallows rely on cavities made by woodpeckers in pine snags and utility poles. By visiting some nests repeatedly, I found that swallows nesting in pine snags were more successful than those nesting in utility poles. I also assessed how swallows interact with the other bird species that create and use nesting cavities. Hairy Woodpeckers usually create cavities in pine snags, while West Indian Woodpeckers use utility poles outside of the pine forest. Swallows nesting in the pine forest compete with fewer bird species for cavities than swallows nesting in other habitats. These results show that managing the forest to retain pine snags and Hairy Woodpeckers is important for the conservation of the swallow.

Anthropogenic activities at coastal areas are assessed to be a major threat to seabirds and associated with habitat degradation and loss, subsequently leading to population declines. After severe floods at the millennial shift a restriction of the water regulation of Lake Vänern, Sweden, with lower variations between high and low water levels was introduced, which has led to an increase of the vegetational cover in the lake’s islands, islets and skerries. Known as important seabird nesting-habitats, the vegetational increase on these islands has been assessed as a threat to the lake’s Laridae-populations and a cause to their negative population growth that has been noticed during the recent decades. Within LIFE Vänern 2014–2018 and an ongoing management strategy of nesting-habitats, 211 of 800 yearly bird-monitored nesting-locations were restored by clearing the locations from all brushwood, bushes and trees. I have evaluated the clearings with the expectation to see a positive long-term effect on the Laridae population growth at cleared compared to uncleared nesting-locations, and foremost on Laridae with a strong colonial nesting-behaviour and thus a strong dependency on open nesting-habitats. Against expectations, I found no difference in the Laridae-population growth at cleared compared to uncleared nesting-locations and thus no significant effects from the clearings on a larger scale, but when analysed by area and species, I found positive effects from the clearings in one of the nine management areas, as for one species (Common Gull) in one area. Moreover, the analysis of small cleared locations (&lt;0.3 ha) revealed a negative correlation with all Laridae and in particular the black-headed gull, indicating that Laridae with a strong colonial nesting-behaviour responded negatively to the clearing of smaller nesting-locations. Turning a population decline of longevity species with low reproduction rates, such as Laridae, is difficult and might be one explanation for the fact that no major positive effects from the clearings could be detected after nine years of the management strategy (2015–2023). The results from the analysis of the clearings rather indicate that other factors might be more important for habitat-selection in the species studied. Moreover, my results show that the availability of nesting-locations might not be the most important factor limiting population growth, and that other factors such as the quality of foraging-habitat, predation or ground-substrate might be more important targets of conservation and population management efforts. / Mänskliga aktiviteter i kust- och strandområden anses utgöra ett stort hot mot sjöfåglar och förknippas med degradering och förlust av habitat, vilket successivt leder till populationsminskningar. Efter omfattande översvämningar vid årsskiftet 2000/2001 infördes en restriktivare vattenreglering av Vänern med minskade variationer mellan hög- och lågvatten, vilket har lett till en ökad tillväxt av sly, buskar och träd på Vänerns många öar, kobbar och skär. Dessa öar, kobbar och skär är kända som viktiga häckningsplatser för sjöfåglar och ökningen av vegetation har bedömts utgöra ett hot mot Vänerns måsfåglar (Laridae) och anses vara en bidragande faktor till den negativa populationsutvecklingen av Laridae som observerats under de senaste decennierna. I LIFE Vänern 2014–2018 och inom ramen för rådande förvaltningsplan för häckningsskär har årligen 211 av 800 sjöfågel-inventerade häckningslokaler restaurerats och all vegetation röjts och avlägsnats för att därefter hållas fria från vegetation. I denna studie utvärderades röjningsåtgärderna av häckningslokalerna med förväntan att se en positiv populationsutveckling på röjda häckningslokaler i jämförelse med icke röjda häckningslokaler samt främst för Laridae med starkt kolonialt häckningsbeteende och stort behov av öppna häckningshabitat. Mot förmodan visade analysen inga effekter från röjningsåtgärderna och att inga signifikanta skillnader i populationsutvecklingen på röjda i jämförelse med icke röjda lokaler i Vänern kunde fastställas i någon större skala. Däremot visade analysen av olika delområden samt på artnivå att positiva effekter kunde urskiljas i ett av nio delområden liksom för en art (fiskmås) i ett av delområdena. Därutöver fastställdes en negativ effekt från vegetationsröjningarna på mindre häckningslokaler (&lt;0.3 ha) och speciellt för skrattmås, vilket indikerar att Laridae med starkt kolonialt häckningsbeteende svarade negativt på röjningsåtgärderna av mindre häckningslokaler. Att vända negativa populationstrender för långlivade arter med låg reproduktionsförmåga är vanskligt och kan vara en orsak till att inte några större positiva långtidseffekter från röjningarna kunde urskiljas efter nio år (2015–2023). Resultaten från analysen av röjningsåtgärderna indikerar snarare att andra faktorer kan vara av större betydelse vid valet av häckningsområde för arterna som studien omfattar. Studien visar även att tillgången till häckningslokaler inte kan ses som en utslagsgivande faktor för en begränsning av negativa populationsutvecklingar utan att beaktning av andra faktorer såsom födosökningsmiljö, predation eller marksubstrat kan vara mer betydelsefulla inom förvaltningen och skyddet av Laridae-populationer.

Examination of bird assemblages along an environmental gradient which encompasses both climate and habitat change is needed if we are to better understand the potential effects of these changes for avians and the ecological process that depend upon them. Climate change is predicted to have a significant impact on deserts and desert margins, resulting in distributional shifts of entire ecosystems and new community associations. This study explores the probable responses of avian communities to increasing desertification. In general, species richness and numbers of birds in arid zones are low compared to more mesic areas. Different combinations of habitat types and the variety of patches in a landscape influence the diversity and community structures of avians in that landscape. The role of vegetation structure in avian habitat selection in semi-arid areas is dictated by horizontal habitat density as well as vertical structure. Although bird distribution is determined by habitat boundaries, most birds are flexible and can disperse across small habitat barriers. The hypothesis tested, was that bird species assemblages along an aridity gradient are affected primarily by rainfall and secondarily by habitat type. Assessing the impacts of rainfall and habitat on bird variables, such as species richness, abundance, diversity, biomass, and life history traits, were the objectives of the study. An east-west aridity gradient of 300 mm, stretching over 370 km, was chosen in central Namibia for the study area. The climate is harsh with localised rain and considerable daily fluctuations in temperature. Grasses, and trees and shrubs up to 7 m in height are the co-dominant life-forms. Surveys were conducted over three years; one winter and one summer survey in each year. Rainfall, seasons and vegetation height were recorded as environmental variables. Three structurally different habitat types were selected for stratified sampling: open areas, rivers and thickets. Open areas were dominated by grass; river refers to ephemeral dry river lines with mature trees; and thickets comprise woody shrubs and trees. At each site, the same three habitats were used for bird sampling, resulting in 15 sample units. Sampling took place on 51 discontinuous line transects of 1km in length and without a width limit. Univariate analyses included ANOVA and t-tests. Multivariate analyses consisted of cluster analysis, MRPP tests, indicator analysis, Shannon diversity index and NMS ordinations. NMS bi-plots were used to define avian community structures responding to aridity, habitat, migration and life history traits. The results showed that bird species richness, abundance, and diversity remained relatively constant across the aridity gradient, until they declined significantly once a certain aridity threshold was crossed at the most arid site. There were significantly more bird species and individual birds at the wetter sites than at the drier sites. Rivers contained more birds than thickened or open habitat types, suggesting the importance of riparian habitat types for maintaining avian diversity. The three more mesic sites included higher numbers of species from the nesting and feeding guilds, regardless of habitat type, than the two more arid sites. The aridity threshold had a significant effect on bird community structures: more migrant and nomadic species, and omnivore and insectivore species persisted in very arid conditions. From the results it was predicted that climate change will cause avian species to undergo range shifts from west to east, resulting in community composition changes and a reduction in diversity. Life history traits affect the adaptive capabilities of bird species and it is predicted that nomadism, flexibility in diet, and adaptability of nesting requirements will contribute to species persistence in the drier conditions predicted under current climate change scenarios. Dry river lines will act as refugia for avian diversity, but crucial habitat types that currently contain less diversity are also important for maintaining unique avian assemblages. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Examination of bird assemblages along an environmental gradient which encompasses both climate and habitat change is needed if we are to better understand the potential effects of these changes for avians and the ecological process that depend upon them. Climate change is predicted to have a significant impact on deserts and desert margins, resulting in distributional shifts of entire ecosystems and new community associations. This study explores the probable responses of avian communities to increasing desertification. In general, species richness and numbers of birds in arid zones are low compared to more mesic areas. Different combinations of habitat types and the variety of patches in a landscape influence the diversity and community structures of avians in that landscape. The role of vegetation structure in avian habitat selection in semi-arid areas is dictated by horizontal habitat density as well as vertical structure. Although bird distribution is determined by habitat boundaries, most birds are flexible and can disperse across small habitat barriers. The hypothesis tested, was that bird species assemblages along an aridity gradient are affected primarily by rainfall and secondarily by habitat type. Assessing the impacts of rainfall and habitat on bird variables, such as species richness, abundance, diversity, biomass, and life history traits, were the objectives of the study. An east-west aridity gradient of 300 mm, stretching over 370 km, was chosen in central Namibia for the study area. The climate is harsh with localised rain and considerable daily fluctuations in temperature. Grasses, and trees and shrubs up to 7 m in height are the co-dominant life-forms. Surveys were conducted over three years; one winter and one summer survey in each year. Rainfall, seasons and vegetation height were recorded as environmental variables. Three structurally different habitat types were selected for stratified sampling: open areas, rivers and thickets. Open areas were dominated by grass; river refers to ephemeral dry river lines with mature trees; and thickets comprise woody shrubs and trees. At each site, the same three habitats were used for bird sampling, resulting in 15 sample units. Sampling took place on 51 discontinuous line transects of 1km in length and without a width limit. Univariate analyses included ANOVA and t-tests. Multivariate analyses consisted of cluster analysis, MRPP tests, indicator analysis, Shannon diversity index and NMS ordinations. NMS bi-plots were used to define avian community structures responding to aridity, habitat, migration and life history traits. The results showed that bird species richness, abundance, and diversity remained relatively constant across the aridity gradient, until they declined significantly once a certain aridity threshold was crossed at the most arid site. There were significantly more bird species and individual birds at the wetter sites than at the drier sites. Rivers contained more birds than thickened or open habitat types, suggesting the importance of riparian habitat types for maintaining avian diversity. The three more mesic sites included higher numbers of species from the nesting and feeding guilds, regardless of habitat type, than the two more arid sites. The aridity threshold had a significant effect on bird community structures: more migrant and nomadic species, and omnivore and insectivore species persisted in very arid conditions. From the results it was predicted that climate change will cause avian species to undergo range shifts from west to east, resulting in community composition changes and a reduction in diversity. Life history traits affect the adaptive capabilities of bird species and it is predicted that nomadism, flexibility in diet, and adaptability of nesting requirements will contribute to species persistence in the drier conditions predicted under current climate change scenarios. Dry river lines will act as refugia for avian diversity, but crucial habitat types that currently contain less diversity are also important for maintaining unique avian assemblages. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Agriculture and, more recently, oil and gas development have contributed to extensive degradation and loss of temperate grasslands. I investigated the landscape-scale effects of oil and gas development, and roads, on grassland birds in southern Alberta using abundance, clutch size and nesting success data collected from 2010-2014. I estimated: (i) the distance at which there are effects of edge, and effects of shallow gas well density, using piecewise regressions; (ii) the locations and extent of habitat affected by infrastructure for obligate grassland species– Baird’s Sparrow (Ammodramus bairdii), Chestnut-collared Longspur (Calcarius ornatus) and Sprague’s Pipit (Anthus spragueii); and generalist species – Clay-colored Sparrows (Spizella pallida), Horned Lark (Eremophila alpestris), Savannah Sparrow (Passerculus sandwichensis), Vesper Sparrow (Pooecetes gramineus) and Western Meadowlark (Sturnella neglecta), and (iii) the total area affected by wells and roads. My findings suggest that the effects of roads, overall, extended to further distances than edge effects associated with natural gas wells, obligate species had more habitat affected by infrastructure than generalist species and shallow gas wells affected more habitat than did oil wells, due to their greater density on the landscape. Additionally, obligates, on average, were negatively affected by proximity to edge where as generalists were more productivity closer to edge. Reducing fragmentation caused by roads, minimizing the spread of non-native vegetation and management of cattle around gas wells could improve habitat quality for these focal species. / February 2016

A B S T R A C T This study examines the impact of catastrophic flood on the species com- position and size of fish prey in the diet of kingfisher (Alcedo atthis) nest- ing in Prague's Botič stream in 2013. Floods in June 2013 affected mainly Bohemia and partly Moravia. The streams across the Vltava river basin, in part of the Elbe river basin and marginally in the Thaya river got swollen. The effect of the flood on the Botič stream was further ampli- fied by draining of water from the dam Hostivař. Hundred and forty year water caused considerable damage to property and it is likely that it also changed the character and size composition of biota, especially fish. This change should be reflected naturally in the diet of kingfisher, which nests and hunts here. The species composition and size of fish prey in the diet of kingfisher before and after the catastrophic flood was investigated from the mass of regurgitated pellets collected from nest tunnels and chambres. In the nesting sediment, 689 head diagnostic bones (pharyngeal bones - ossa pharyngea and preopercual bones - praeoperculare) were found before the flood on Botič stream in June 2013. These bones belonged to 10 fish species and 3 families (Cyprinidae, Percidae and Balitoridae). The average length of fish was 6,5 cm, average weight 2,6 g, and the index of...

O problema de empacotamento em faixas de peças irregulares consiste em cortar um conjunto de peças bidimensionais a partir de um objeto de largura fixa utilizando o menor comprimento possível. Apesar de sua importância econômica para diversos setores industriais, há poucos trabalhos que abordam o problema de forma exata devido a sua dificuldade de resolução. Recentemente, Toledo et al. (2013) propuseram um modelo inteiro misto para este problema, no qual as peças são posicionadas em uma malha de pontos. Este modelo obteve bons resultados, provando a otimalidade para instâncias com até 21 peças. No entanto, o modelo possui um grande número de restrições de não-sobreposição, que cresce rapidamente de acordo com a discretização utilizada e a quantidade de peças distintas que devem ser alocadas. Neste trabalho, são propostas novas formulações matemáticas baseadas neste modelo, com o objetivo de reduzir o número de restrições. Na primeira abordagem, são propostos dois modelos reduzidos que mostraram ser eficientes para instâncias com poucas repetições de peças. Na segunda abordagem, foi proposto um modelo de cobertura por cliques para o problema. Este modelo obteve desempenho igual ou superior ao modelo da literatura para todas as instâncias avaliadas, obtendo uma solução ótima para instâncias com até 28 peças. / The irregular strip packing problem consists of cutting a set of two-dimensional pieces from an object of fixed width using the smallest possible length. Despite its economic importance for many industrial sectors, few exact studies have been made on this problem due to its difficulty of resolution. Recently, Toledo et al. (2013) proposed a mixed-integer model to this problem in which the pieces are placed on a grid. This model has worked successfully proving the optimality for instances up to 21 pieces. However, the model has a large number of non-overlapping constraints, which grows quickly in accordance with the discretization resolution and number of distinct pieces. In this work, we propose new mathematical formulations based on this model in order to reduce the number of constraints. In the first approach, we present two reduced models that have shown to be effective for instances with few repetitions of pieces. In the second approach, it was proposed a clique covering model for the problem. This model achieved a greater or equal performance than the literature for all instances, getting an optimal solution for instances up to 28 pieces.

Um dos maiores desafios da Astrofísica é tentar compreender a complexidade da composição química das estrelas. Elementos com massas atômicas acima de A>60 são formados pelos chamados processos de captura de nêutrons (processo-s e processo-r). A presença destes em espectros de estrelas de baixa massa (longo período de vida) e com pouco conteúdo metálico sugere episódios de enriquecimento por estrelas massivas nos primórdios da Galáxia. Portanto, o estudo das estrelas chamadas \"pobres em metais\" enriquecidas por elementos formados por captura de nêutrons pode reproduzir as condições físicas dominantes à época de sua formação. O objetivo deste trabalho é explorar os padrões de abundâncias das estrelas muito pobres em metais observadas no survey HERES. Através deste estudo, é possível inferir correlações entre elementos químicos e restringir a operação dos processos de captura de nêutrons na Galáxia. Para tanto, utiliza-se técnicas estatísticas como a análise de conglomerados, que permite o estudo da formação de grupos naturais baseado na relação entre as abundâncias elementais. Este estudo fornece uma análise compreensiva de uma amostra de 382 estrelas pobres em metais, além de introduzir duas novas subclasses para estrelas pobres em metais enriquecidas em elementos formados por captura de nêutrons. / One of the most challenging subjects of Astrophysics is trying to understand the complexity of the chemical composition of stellar objects. Spectroscopic observations are widely used nowadays in order to achieve these goals, as they provide the chemical composition of the atmosphere of the stars. Elements with atomic masses above A>60 are formed by the so called neutron capture processes (r-process and s-process). Its presence on low-mass star spectra (which have long life-time) and low metal content suggests episodes of enrichment by high-mass stars that took place in the early times in the Galaxy formation. Then, the study of those \"metal-poor\" stars enriched by neutron-capture elements may help reproduce the physical conditions of the environment from where they were formed. The main goal of this project is to explore the abundance patterns of the very metal-poor stars observed by the HERES survey. This study allows the analysis of the correlations between chemical elements and place some constraints on the operation of the neutron capture processes in the early Galaxy. This approach made use of statistical tools, such as agglomerative nesting, which can identify the formation of natural groups based on relations among elemental abundances. In this context, this study provides a comprehensive analysis of a 382 metal-poor stars sample, and introduces two new subclasses for metal-poor stars with determined abundances of neutron-capture elements.