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Stearns, Danielle Marie 1969. "Bird abundance as an indicator of habitat quality for breeding birds." Thesis, The University of Arizona, 1995. http://hdl.handle.net/10150/278475.
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Reproductive success and survival of birds often are impractical to measure. Therefore, biologists frequently rely on measures of bird abundance alone to evaluate habitat quality for breeding birds. I examined whether results from standard survey techniques for birds during the breeding season reflected number of nesting pairs and reproductive success of 5 passerine species. Abundance of 3 species was positively associated with number of nesting pairs, but the relationship between abundance and reproductive success varied among these species. Differences in detectability of breeding males may partly explain why abundance and number of nesting pairs were related in some species and not in others. Variations in the availability and quality of habitat patches among plots could produce the different relationships I observed between abundance and reproductive success. My results suggest that measures of reproductive success as well as abundance should be used to determine habitat quality for breeding birds.
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Latta, Steven C. "Ecology and population regulation of neotropical migratory birds in the Sierra de Bahoruco, Dominican Republic /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9998494.
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Blackburn, Emma. "The wintering and migration ecology of the whinchat Saxicola rubetra, a declining Palearctic migrant." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/11859.
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For migrant birds, the non-breeding season can greatly influence survival and future reproductive success. Knowledge of annual and overwinter survival, the degree of site fidelity and habitat use in the non-breeding season, migration ecology, routes and stopovers, and whether these differ with age or sex is fundamental to understanding population dynamics, vulnerability to anthropogenic habitat degradation, and consequently for understanding the severe widespread declines of migrant bird species. The degree to which a migrant is a winter specialist or generalist is likely to be central to understanding population dynamics. I studied survival rates and the wintering and migration ecology of a declining Palearctic migrant, the whinchat Saxicola rubetra, wintering in West Africa, to establish how the non-breeding season may influence migrant population dynamics. Whinchats were extremely site faithful to both within and between years, holding distinct winter territories and returning to those territories in subsequent winters, despite the opportunity to relocate. Overwinter survival was very high and annual survival was comparable to or higher than that reported on the breeding grounds. Because our power to detect resident and dispersing birds was high, survival rates likely estimated true survival well. Habitat characteristics varied widely across territories and territories were smaller if more perching shrubs and maize were present. Most individuals showed a tolerance or even preference for human modified habitats. Some individuals may have multiple wintering sites. There was no evidence of dominance-based habitat occupancy or any differences in winter ecology, site fidelity, survival and most aspects of migratory behaviour between age and sex classes. Migratory connectivity occurred only on a large-scale and individual migratory behaviour was also varied. Fundamentally, the results suggest a generalist strategy in the non-breeding season within their wintering habitat of open savannah, most likely as an adaption to stochastic site selection within the wintering range for juveniles undertaking their first migration plus changing and unpredictable conditions both within and between years. Consequently, wintering conditions may not significantly limit whinchat populations and mortality is probably highest during active migration. Notably, non-specialist migrants such as whinchats may have some resilience at the population-level to the increasing anthropogenic habitat modification occurring in Africa, suggesting that conditions during migration and in Europe may be driving declines; yet establishing the currently unknown thresholds of any resilience is likely to be fundamental for the future conservation migrants.
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Noel, Brandon Lennon. "The winter ecology of the piping plover (Charadrius melodus) in coastal Georgia." Connect to this title online (Georgia Southern site) Connect to this title online (U.S. Fish & Wildlife Service site), 2006. http://www.fws.gov/nc-es/birds/Noel_2006_MSThesis.pdf.
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Sayol, Altarriba Ferran. "Causes and consequences of brain size evolution: a global analysis on birds." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/565697.
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Per què alguns llinatges de vertebrats, incloent els humans, han evolucionat cervells grans és un dels grans trencaclosques de la biologia evolutiva. De les varies hipòtesis que s’han plantejat per intentar resoldre aquest misteri, la variació ambiental destaca com una de les principals causes de la variació en la mida relativa del cervell. Més formalment, la hipòtesis del cervell protector (CBH, de Cognitive buffer hypothesis”, en anglès) postula que els cervells relativament més grans han evolucionat per facilitar els ajustos de comportament per augmentar la supervivència en condicions canviants. Tot i que la CBH ha rebut suport empíric els darrers anys, alguns autors qüestionen la seva rellevància for explicar l’evolució del cervell argumentant que mantenir un cervell massa gran en períodes d’escassetat de recursos és massa costós, de manera que la variació ambiental hauria de limitar més que no pas afavorir l’evolució dels cervells grans. Aquesta tesi doctoral explora les causes i conseqüències de l’evolució de la mida del cervell, amb especial atenció en la CBH, validant les seves assumpcions, assajant les seves prediccions i avaluant les seves implicacions. La tesi treu profit d’una base de dades de mesures del cervell per més de 1900 espècies d’ocells en combinació amb els més recents mètodes filogenètics comparatius per tal de descobrir els orígens de la variació en la mida del cervell en la classe de vertebrats més diversa. Com a primer objectiu, aquesta tesi valida en quina mesura la mida relativa del cervell és una bona aproximació de la variació en estructures del cervell involucrades en la capacitat de construir respostes de comportament als nous reptes. El capítol 1 mostra que les àrees associatives del cervell, tradicionalment relacionades amb la intel·ligència general, són desproporcionadament més grans en espècies de cervell gran i poden predir de forma acurada la variació en el conjunt del cervell, de manera que es validi la seva utilització en anàlisis comparatives globals. Segons la CBH, les espècies que viuen en regions amb alta variabilitat ambiental haurien de ser seleccionades per cervells grans, a menys que tinguin adaptacions especialitzades per evadir les caigudes en la disponibilitat de recursos. El Capítol 2 mostra com els ocells que viuen en ambients més estacionals i impredictibles , com les regions de latituds altes, posseeixen cervells relativament més grans que els residents d’altres regions, recolzant la CBH en ocells. En el capítol 3 es mostra com els ocells que colonitzen illes oceàniques sembla que han evolucionat cervells relativament més grans que els seus parents continentals. Aquests canvis sembla que en part s’expliquen per un augment de la incertesa en la disponibilitat de recursos que caracteritza les illes, aportant una evidència addicional per la CBH. En el capítol 4 s’estudia el rol actiu del cervell en l’evolució. Tal com prediu la hipòtesi del behavioural drive (behavioural drive hypothesis en anglès), els ajustos de comportament més freqüents com a resposta als reptes ambientals hauria d’exposar els individus més sovint a nous conjunts de pressions selectives, tot afavorint la divergència evolutiva respecte els seus ancestres i finalment afavorint l’aparició de noves espècies. El capítol 4 mostra com els llinatges amb cervells relativament més grans han tingut majors taxes de diversificació taxonòmica. Aquesta troballa recolza així la idea que els animals no són agents passius de la selecció, però que poden modificar activament la seva relació amb l’ambient i influenciar el seu propi camí evolutiu. En resum, els resultats d’aquesta tesi aporten evidència empírica per la CBH, mostrant com els cervells relativament més grans funcionen, i per tant han evolucionat, per fer front als canvis ambientals, i que l’evolució de cervells grans pot a més influir en la diversificació evolutiva d’un llinatge.Why some vertebrate lineages, including humans, evolved large brains is one of the main puzzles in evolutionary biology. Of the many hypotheses that have been launched to try to resolve this puzzle, environmental variability stands out as a major cause of relative brain size variation. More formally, the cognitive buffer hypothesis (CBH) postulates that relatively large brains evolved to facilitate behavioural adjustments to enhance survival under changing conditions. The rationale of the CBH is that advanced cognition can increase fitness in varying environments by enhancing information gathering and learning, facilitating for instance shifts between different feeding sites or food types to alleviate periods of food scarcity. While the CBH has received ample empirical support in recent years, some authors have questioned its relevance to account for the evolution of enlarged brains on the grounds that maintaining the brain during periods of food scarcity may be excessively costly, so environmental variability should constrain rather than favour the evolution of large brains. The present PhD thesis explores the causes and consequences of the CBH, validating its assumptions, testing its predictions and assessing its evolutionary implications. It takes advantage of a large database on brain size comprising more than 1900 extant bird species in combination with recently developed phylogenetic comparative methods to elucidate the origins of brain size variation in the most diverse vertebrate class. As a first objective, the thesis validates the extent to which relative brain size is a good proxy of the brain structures involved in the capacity to construct behavioural responses to new challenges. Chapter 1 thus shows that the associative areas of the brain, classically related with general intelligence, are disproportionally larger in large brained species and accurately predict variation in the whole brain, therefore validating its use in broader comparative analyses. According to the CBH, species living in regions with higher environmental variation should be selected for larger brains, unless they have adaptive specialisations to avoid drops in resource availability. Chapter 2 shows that birds living in highly seasonal and unpredictable environments, like high-latitude regions, possess relatively large brains than residents from other regions, supporting the CBH in birds. Additional support for the hypothesis is found in Chapter 3, where birds colonizing oceanic islands seem to evolve relatively larger brains than their continental relatives. These changes seem to be in part caused by the increased uncertainty in resource availability that characterizes islands, which together with limited chances to disperse and a trend toward slower life-history strategies can facilitate the evolution of enlarged brains. Finally, Chapter 4 explores the active role of brain size on evolution. As predicted by the behavioral drive hypothesis, frequent behavioral changes as a response to environmental challenges should expose individuals to new sets of selective pressures, thereby favouring evolutionary divergence from the ancestors. Chapter 4 provides evidence for the behavioural drive hypothesis, showing that avian lineages with relatively large brained have experienced higher diversification rates than those with smaller brains. This finding is in line with the view that animals are not passive agents of selection, but by actively modifying its relationship with their environment also influence their own pace of evolution. Overall, the findings of the present thesis provide empirical support for the CBH, showing that a relatively large brain functions, and hence may have evolved, to cope with environmental changes, and that the evolution of enlarged brains may subsequently influence the evolutionary diversification of the lineage.
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Salisbury, Claire L. "Ecology and diversity of Amazonian birds." Thesis, University of Oxford, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596091.
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The Amazon rainforest harbours -10% of the world's birds, and more than 400 species are regularly recorded at single sites. Understanding the processes behind the generation and maintenance of biodiversity, especially on this scale, has been a central theme in the study of evolution and ecology since Darwin. Amazonian speciation and diversification models emphasise the importance ofhiogeography, geological history, and interspecifi c interactions in generating one of the most biodivcrse biomes on earth. However, the inherent ecological traits of Amazonian taxa are rarely considered. The role of rivers in Amazonian diversification is contentious, and are-evaluation of the river barrier hypothesis in the light of species ecology is timely, as behavioural, distributional and phylogenetic data for Amazonian birds are more detailed and robust than ever before. By examining the relationship between 20 major rivers and the distribution of 739 species and their subspecies in a comparative framework, I investigate (i) the role of the Amazonian river system in shaping and driving av ian diversification; (ii) how river dynamics affect river barrier strength; and (ii i) how ecology influences clade diversification propensity. I also examine (iv) how niche space is shared and partitioned, in a case study investigating mechanisms pennilting the coexistence of two closely related species of antbird. I demonstrate that rivers act as important barriers for particular ecological groups, and are stronger baniers for subspecies than species, indicating a role in recent and ongoing intraspecific diversification; that barrier strength increases with river width; Ihal dispersal limitation is a key predictor of divers ification, with higher subspecies richness in groups with poor dispersal; and that species coexistence is mediated by high levels of niche overlap. Taken together, these studies suggest that species ecology, dispersal limitation and river barriers interact to playa major role in structuring, generating and maintaining Amazonian avian biodiversity.
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Gibson, Michelle Rene. "Movement ecology of Australian arid-zone birds." Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12778/.
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The movements of nomadic species are poorly understood, being highly dynamic over time and space. There is an urgent need to better understand this group as current conservation approaches appear not to be providing adequate protection. In this thesis, I evaluate a survey method to monitor this dynamic group, assess environmental variables driving their movements over time, and explore how rainfall structures the overall avian community. To date, no standardized, large-scale monitoring has been carried out for arid zone or nomadic species. In Chapter 2, I describe a protocol for surveying this group over five years using two survey methods. Detection probabilities and robust density estimates were generated for 64 species and showed the majority fluctuated markedly over time. Line transect surveys were more effective for species richness and abundance measures. This survey method provides the first standardized density estimates for this assemblage and can be easily repeated in future for this and other remote, arid biological communities. The movement characteristics of species with unpredictable, aseasonal movements are very poorly understood and difficult to measure. In Chapter 3, I develop a method for quantifying extent of bird movement by analysing changes in species’ site persistence and variability in inter-annual densities over time, and compare results with existing movement classifications. Continuous variation in extent of species movement indicated that a binary grouping of resident versus nomadic species is inappropriate. Existing movement classifications likely underestimate species movements within arid regions of their distribution, suggesting that caution is needed when using sweeping species-level classifications, especially for Australian birds whose movements can be heavily environment-dependent. Unlike regular migration, which is triggered by seasonal cues such as day length and temperature, movement in nomads is thought to be triggered by less predictable environmental conditions. In Chapter 4, I explore the relative influence of dynamic and static environmental variables on species abundance. Dynamic variables were more important for nomadic versus resident species but static variables were equally important for nomadic and resident species. These findings suggest that habitat structure is important to consider in addition to dynamic environmental features for understanding nomadic species movements. Pulse events are thought to be positively correlated with nomadic species movements and to play an important role in structuring arid biological communities. In Chapter 5, I investigate how structural changes observed in Australia’s arid bird community relate to rainfall and vegetation greenness. The importance of rainfall was mediated through vegetation growth and the community is dynamic at a local level but exhibits stability at a landscape level, underscoring the importance of connectivity between suitable habitats within this landscape to enable species to reshuffle among sites. In sum, my thesis highlights the importance of standardized data for enabling an empirical approach to understanding nomadic and arid-zone bird species. Findings will advance our understanding of these species’ dynamics and lay groundwork for improving protection of this group by identifying further research priorities.
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Tracey, John Paul. "Ecology, impacts and management of pest birds." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/5187/.
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Pests can impact significantly upon the economy, the environment and on human and animal health. However, for pest birds there are surprisingly few studies of these impacts and how to reduce them. The aim of this thesis is to advance our understanding of the ecology, impacts, and management of pest birds using case studies for each of the three main impacts. In considering economic impacts I estimate pest bird abundance, describe a novel method for measuring bird damage, and evaluate the efficacy of lethal and non-lethal methods in vineyards and orchards. Using data across 185 property years, netting was found to be the most effective in reducing bird damage. Shooting was not as effective but was one-third of the cost and had 13% lower damage compared with nil-treatments. Scaring with electronic devices and visual deterrents had no effect on bird damage. Despite their widespread use, lethal methods had limited effectiveness for reducing pest abundance. In considering environmental impacts introduced mallards on Lord Howe Island were used as a case study. Phenotypic characteristics suggest that mallards have supplanted the native Pacific black duck on Lord Howe Island. Management alternatives are evaluated and discussed. In considering health-related impacts wild birds and avian influenza in Australia was used as a case study. Here, the ecology of Australia’s Anseriformes, and the epidemiology, modes of transmission, and the factors influencing the prevalence of avian influenza in Australia’s wild birds are investigated. Risk profiles to improve the efficiency and relevance of wild-bird surveillance are also provided. The case studies presented demonstrate that an understanding of a pest’s ecology, efficient measures of impacts, and thorough evaluations of surveillance and management strategies are essential for effectively managing their economic, environmental and health-related impacts.
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Cooper, Tessa June Groves. "The effects of land use changes on the distribution of forest dependent bird species in South Africa." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97842.
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Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Forests in South Africa have had a long history of human utilization and disturbance, and are under threat from a variety of anthropogenic land use changes. Foremost of these are deforestation and forest degradation, impacting the species native to these forests. The aims of this study were to determine changes in the distribution of forest dependent bird species according to the South African Bird Atlas Project; to relate these changes to changes in land-use; to identify links between these changes; to determine the extent, location and causes of the decline of each forest dependent bird species; and to identify current risks to forest dependent bird species in South Africa. Range data on 57 forest dependent bird species from SABAP1 (1987-1992) and SABAP2 (2007-present) were analyzed. Of these, 28 species were found to have declining ranges. Thirty sites across South Africa were identified as being most at risk, with all having experienced a loss of more than 10 of the 57 forest dependent bird species between SABAP1 and SABAP2. The range change data of the 28 species with decreasing ranges were correlated with data on changes in land cover over the same time period to infer relationships between changes in land use and change in bird ranges. Occupancy modelling was done to determine which land cover types affect extinction and initial presence. Individual species characteristics were analyzed to determine links between characteristics and response to land use change. A pan-European trait-based risk assessment framework was applied to all 57 species to identify habitats and species most at risk, as well as the most important threats to species persistence. Results showed that natural vegetation decreased in 67% of sites, while plantations and cultivation increased in 50% of sites. Occupancy modelling showed extinction likelihood to increase with plantations in some species, while plantations mitigated extinction likelihood in other species. Urbanization and cultivation likewise mitigated extinction likelihood in some species. Natural vegetation was replaced by cultivation, while cultivation was replaced by urbanization. The number of species lost increased with a loss of natural vegetation. Twenty two of the thirty sites experienced deforestation of indigenous forests between 2000 and 2013/2014; changes in natural vegetation in these sites can be attributed primarily to deforestation, and a loss of plantations. While most at-risk sites were in the Eastern Cape, there was no geographic grouping of species loss or of land use change. Most species lost were birds of prey or insectivores, and species characteristics and habitat preferences determined the sites from which they were lost. The Cape parrot (Poicephalus robustus), rufous-chested sparrowhawk (Accipiter rufiventris) and the migratory Eurasian golden oriole (Oriolus oriolus) suffered the largest declines in range size and are thought to be most at risk. Montane forests were found to be more at risk than other forest types. The major risks facing montane forests were increased abundance of small predators, increased fire suppression, increased soil management, removal of deadwood and reduced diversity of tree species. These threats are all products of plantation forestry and local harvesting. Nesting risk was higher than foraging risk for all species, indicating that nesting habitat should be better preserved. Half of South Africa’s forest dependent bird species have declining ranges, with the loss of these species most prominent in the Eastern Cape. Natural vegetation loss, comprising mostly recent deforestation; increased cultivation and urbanization; and changes in plantation cover are thought to be the main factors determining these declines. Montane forests in particular should be better protected to preserve forest dependent species, and the negative effects of plantation forestry and local harvesting should be mitigated.
AFRIKAANSE OPSOMMING: Suid-Afrika het ‘n lang geskiedenis van woude wat deur mense gebruik, asook vernietig word. Woude word bedreig deur verskeie menslike grondgebruike en veranderinge. Die mees vooraanstaande van die bedreigings is ontbossing en woud verdunning, wat ‘n invloed het op inheemse spesies in die woude. Die doelwitte van hierdie studie was om veranderinge in die verspreiding van bos-afhanklike voëlspesies vas te stel volgens die Suid Afrikaanse Voël Atlas Projek; om hierdie veranderinge te verband met veranderinge in grondgebruik; om verbande tussen hierdie veranderinge te identifiseer; om die mate, die plek en die oorsake van die agteruitgang van elke bos-afhanklike voëlspesies te bepaal; en om huidige risiko's aan die bos afhanklik voëlspesies in Suid-Afrika te identifiseer. Trefwydte inligting oor 57 woud afhanklike voëlspesies van SABAP1 (1987-1992) en SABAP2 (2007-nou) was geanaliseer. Daar was gevind dat vanuit die spesies, het 28 ‘n afneming in trefwydte ervaar. Dertig terreine in Suid-Afrika was uitgeken as dié met die hoogste risiko, met ‘n verlies van meer as 10 van die 57 woud afhanklike voëlspesies tussen SABAP1 en SABAP2. Die trefwydte inligting van die 28 spesies met ‘n afnemende trefwydte was gekorreleer met inligting oor veranderinge in grond bedekking oor dieselfde tydperk om verhoudings tussen veranderinge in grond gebruik en veranderinge in voël trefwydtes aftelei. Besetting modellering was gedoen om te bepaal watter tipes grond bedekking beinvloed uitwissing en aanvanklike teenwoordigheid. Kenmerke van individuele spesies is ontleed om verbande tussen kenmerke en reaksie op verandering in grondgebruik te bepaal. ‘n Pan-Europese eienskap gebaseerde risiko-analise raamwerk is toegepas op die 57 spesies om die spesies en habitatte met die grootse risiko te identifiseer, asook die belangrikste bedreigings vir spesies-volharding. Die resultate het gewys dat natuurlike plantegroei het verminder in 67% van terreine, terwyl plantasie en verbouing vermeerder het in 50% van terreine. Besetting-modellering het gewys dat waarskynlikheid van uitwissing vermeerder met plantasies in sommige spesies, terwyl plantasies die waarskynlikheid van uitwissing verminder het in ander spesies. Verstedeliking en verbouing het ook die waarskynlikheid van uitwissing verminder in sommige spesies. Natuurlike plantegroei was vervang deur verbouing, terwyl verbouing vervang is deur verstedeliking. Die aantal spesies verlies het vermeerder met die vermindering van natuurlike plantegroei. Twee en twintig van die dertig terreine het ontbossing van inheemse woude ervaar tussen 2000 en 2013/2014. Veranderinge in natuurlike plantegroei in die terreine is meestal as gevolg van ontbossing, en ‘n vermindering van plantasies. Terwyl meeste van die hoë risiko terreine in die Oos-Kaap was, was daar geen geografiese groepering van spesies vermindering of grondgebruik veranderinge nie. Meeste spesies wat vernietig is was roofvoëls of insectivore, en spesies kenmerke en habitat voorkeure het die terreine bepaal waaruit hulle verloor is. Die grootpapegaai (Poicephalus robustus), rooiborssperwer (Accipiter rufiventris) en die trekvoël Europese wielewaal (Oriolus oriolus) het die grootste vermindering in trefwydte grootte ervaar, en is vermoedelik die grootste risiko. Bergwoude was gevind om meer in gevaar te wees as ander woud tipes. Die grootste risikos wat bergwoude beïnvloed het was ‘n toenemende hoeveelheid klein roofdiere, verhoogde vuur onderdrukking, verhoogde grondbestuur, verwydering van dooie hout, en verlaagde diversiteit van boomspesies. Hierdie bedreigings is almal as gevolg van plantasie bosbou en plaaslike oes. Nes-risiko was hoër as kos soek risiko vir alle spesies, wat aandui dat nes-habitat beter bewaar moet word. Die helfte van Suid-Afrika se woud-afhanklike-voëlspesies het dalende trefwydtes, met die verlies van hierdie spesies mees opvallend in die Oos-Kaap. Die verlies van natuurlike plantegroei, as gevolg van onlangse ontbossing; verhoogde verbouing en verstedeliking; en veranderinge in plantasie bedekking is vermoedelik die hooffaktore wat die vermindering van voëlspesies veroorsaak. Veral bergwoude moet beter beskerm word om woud-afhanklike-voëlspesies te bewaar en die negatiewe invloede van plantasiebosbou en plaaslike oes te verminder.
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Mazzei, Benjamin A. "Monitoring birds and habitat in early-successional sites in Connecticut." Amherst, Mass. : University of Massachusetts Amherst, 2009. http://scholarworks.umass.edu/theses/229/.
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Ko, Wai-ping Ice. "The nutritional ecology of frugivorous birds in Hong Kong /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20667747.
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Brown, Robert Jeffrey. "BIRD STRIKE HAZARDS AT AIRPORTS AND ASSESSMENT OF BIRD STRIKES AT A MIDWESTERN AIRPORT: 2000-2007." Miami University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1229046725.
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Shoji, Akiko. "Incubation strategy in marine birds." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28466.
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The incubation shift length of the Ancient Murrelet ( Synthliboramphus antiquus), an exceptionally long and varied for an auk. I studied colonies of this species at East Limestone Island (1993-1995, 2002-2003: data collected by Laskeek Bay Conservation Society) and Reef Island (2007-2008), Haida Gwaii, British Columbia. Incubation shift length was correlated between pair members and my results show that maintaining incubation schedule was an essential component of reproductive success. Incubation shift length varied in response to prevailing local weather and sea conditions (e.g. wind speed, wave height), perhaps as a consequence of reduced foraging efficiency. Incubation shift length was longer in years when sea surface temperature in April was high. In years with longer shift, birds had lower reproductive success and chicks departed the nest with a lower body mass. My results explained if we assume that multi-day incubation shifts in Ancient Murrelets are the adaptively preferred strategy, through reduction in predation risk, but that actual shift lengths are modified by immediate weather and foraging constraints.
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Kayello, Lima. "Opportunism and cognition in birds." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119422.
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Animals vary in their response to the distribution of resources in time and space. Opportunistic foraging is evident in many species and has indirectly been shown to be linked to measures of cognition such as innovation and problem solving. However, in the field of cognitive ecology, the operationalization and empirical use of opportunism is problematic. In chapter 1, I review the concept of opportunism in the zoological literature and propose an operational definition. The review suggests that many definitions of the concept are not useful, in particular those that equate it with generalism or use it to describe random choice in foraging. With the operational definition I propose ('latency to switch to a new, abundant, food source'), the relationship between ecological flexibility and cognition is then addressed through a small-scale comparative study in chapter 2. Here, the purpose is to determine if an opportunistic species will perform better at problem solving, and have lower neophobic tendencies, than a less opportunistic species. The study compares two sister species of Thraupidae with different foraging strategies: the Barbados bullfinch (Loxigilla barbadensis), an opportunistic forager, and the black-faced grassquit (Tiaris bicolor), a conservative forager. In the field, I carried out focal observations along with opportunism and neophobia experiments. In captivity, wild-caught individuals were run through a set of behavioural and cognitive tests, which included a neophobia test and a problem-solving obstacle removal task. Results show that although both species share overlapping foraging modes, territorial habits and neophobic tendencies, the Barbados bullfinch is much more opportunistic, bolder and better at problem-solving than the black-faced grassquit.Les animaux diffèrent dans leurs réponses à la distribution spatiale et temporelle des ressources. Plusieurs espèces manifestent un mode opportuniste de quête alimentaire et des preuves indirectes suggèrent que l'opportunisme est associé à des mesures de cognition telles que l'innovation et la résolution de problèmes. Toutefois, dans le domaine de l'écologie cognitive, la définition et l'opérationalisation de l'opportunisme pose problème. Dans le premier chapitre de ce mémoire, je fais une revue de littérature du concept d'opportunisme et j'en propose une définition opérationelle. La revue suggère que plusieurs acceptions du concept sont peu utiles, en particulier celles qui le confondent avec le concept de 'genéralisme' et celles qui lui donnent le sens de 'capture au hasard' de proies. A partir de la définition opérationelle que je propose ('la latence d'exploitation d'une nouvelle et abondate source de nourriture'), la relation entre l'opportunisme et la cognition est testée au chapitre 2 dans une étude comparative à petite échelle. Je prédis qu'une espèce opportuniste sera plus rapide à résoudre un problème alimentaire et sera moins néophobe qu'une espèce conservatrice. L'étude compare deux espèces génétiquement très proches, le sporophile de la Barbade (Loxigilla barbadensis), une espèce opportuniste, et le sporophile cici (Tiaris bicolor), une espèce conservatrice. J'ai effectué sur le terrain des observations focales et des expériences sur l'opportunsime et la néophobie. En captivité, j'ai soumis des individus piégés sur le terrain à des tests de néophobie et d'enlèvement d'obstacle pour atteindre de la nourriture. Les résultats révèlent que le sporophile de la Barbade est plus opportuniste, moins néophobe et meilleur à résoudre le problème que le sporophile cici, mais que ni sa territorialité ni son mode d'alimentation sur le terrain ne diffèrent suffisamment de celui du sporophile cici pour expliquer les différences de cognition.
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Elliott, Kyle Hamish. "How can birds live long and hard? patterns in the physiology and behaviour of aging birds." Company of Biologists, 2013. http://hdl.handle.net/1993/22283.
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As animals age, they are expected to invest successively more energy in reproduction as they have fewer subsequent chances to reproduce (the “restraint” hypothesis). Conversely, the oldest animals may show restraint in reproduction because even a small increase in energy expended during reproduction may lead to death. Alternatively, both young and very old animals may lack the ability to maintain high levels of energy expenditure (the “constraint” hypothesis), leading to reduced reproductive success. Many studies have observed an increase in reproductive success with age followed by a reduction at the end of life, but fewer studies have examined the proximate mechanisms, which provide a context for understanding ultimate causes. I examined over 30 behavioural and physiological metrics of aging in two species of free-living long-lived seabirds (thick-billed murres Uria lomvia and black-legged kittiwakes Rissa tridactyla) and a short-lived passerine (tree swallows Tachycineta bicolor). For all species, reproductive success was high at intermediate ages. In support of the “restraint” hypothesis, when birds were stressed glucocorticoid hormones, which direct energy away from reproduction and towards survival, were higher in young birds (swallows) and both young and very old birds (kittiwakes and murres). When birds were handicapped older birds expended more energy. When challenged exogenously, there was no change in hormone levels with age, implying that they were “choosing” to be restrained. Resting metabolic rate (RMR) declined linearly with age in both seabird species. T3, which I show is indicative of RMR in birds, also declined with age, demonstrating that the reduction in metabolism was strategic and not due to changing body composition. In contrast, daily energy expenditure in both seabird species during breeding was constant with age while antioxidant capacity became elevated during middle age, and further increased with age. Several measures of behavioural performance did not vary with age. I conclude that hormonal cues lead to greater investment in adult’s energy stores over its offspring’s energy reserves (restraint hypothesis) at the start of life. At the end of life, both hypotheses were supported; energy expenditure was constrained by senescence, leading to increased restraint in investing additionally in offspring.
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Somveille, Marius. "The global ecology of bird migration : patterns and processes." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709448.
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Lock, Nga Yi, and 駱雅儀. "The ecology of urban birds in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31240665.
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Donaldson, Lynda. "Conservation and ecology of wetland birds in Africa." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/31812.
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Conservation managers worldwide are increasingly faced with the challenges of managing and protecting fragmented landscapes, largely as a consequence of human activities. Over recent decades, ecological theory has made a significant contribution to the development of landscape-scale conservation and practice. However, recommendations accounting for what is practically achievable in the modern-day landscape are currently lacking, while criteria for conservation planning and prioritisation continue to neglect the role of habitat networks at the required spatial scale for the long-term persistence of biodiversity. In this thesis, I test and apply ideas surrounding the complexities of managing and conserving species in a landscape context, using a suite of bird species endemic to papyrus (Cyperus papyrus) swamps in East and Central Africa as a model system. In the face of large-scale habitat loss and degradation, practical measures that account for the fragmented nature of this system, the needs of multiple specialist species, and the reliance on this habitat by local people, are urgently required. I first review the concepts originating from reserve design theory to provide a decision-making framework for those involved in landscape-scale conservation amid 21st century challenges to biodiversity, highlighting the key principles to be considered for informed choices to be made. Second, I show that the needs of local people can be compatible with conservation planning in the tropics, and may play an important part in maintaining habitat quality for species residing in historically disturbed landscapes. Third, I develop a novel framework to make an explicit link between metapopulation dynamics and conservation planning. Despite differences in the patch-level dynamics of individual species, areas of habitat where populations of multiple species are resistant to extinction, and resilient because of high chances of (re)colonization can be identified, highlighting where resources could be invested to ensure species have the capacity to respond to future change. Finally, I simulate the metapopulation dynamics of the papyrus-endemic birds to demonstrate that the optimal conservation strategy for the long-term persistence of all species residing in a network depends on the characteristics of individual species, and the total area that can be protected. Overall, this thesis develops and tests the ecological theory used in spatial conservation planning, emphasising the importance of habitat disturbance and interspecific ecological differences for the effective management of habitat networks. The results increase the evidence base for the conservation of wetland birds in Africa, as well as for species residing in fragmented landscapes more generally.
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Lock, Nga-yi. "The ecology of urban birds in Hong Kong /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B22424945.
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Sabol, Thomas David. "Effects of Western Juniper (Juniperus occidentalis) removal on avian species composition in shrub-steppe habitat in south-central Oregon." View full-text version online, 2005. http://soda.sou.edu/awdata/060221a1.pdf.
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Thesis (M.S.)--Southern Oregon University, 2005."A thesis submitted to the Department of Biology of Southern Oregon University in partial fulfillment of the requirements for the degree of Master of Science in Environmental Education." Includes bibliographical references (p. 36-50) Also available via Internet as PDF file through Southern Oregon Digital Archives: http://soda.sou.edu. Search Bioregion Collection.
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Rodríguez-Ferraro, Adriana. "Community ecology and phylogeography of bird assemblages in arid zones of northern Venezuela implications for the conservation of restricted-range birds /." Diss., St. Louis, Mo. : University of Missouri--St. Louis, 2008. http://etd.umsl.edu/r3141.
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May, Celia A. "VNTR studies of birds of prey." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358003.
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Logie, John W. "Population ecology and lifetime reproductive success of dippers Cinclus cinclus." Thesis, University of Stirling, 1998. http://hdl.handle.net/1893/26684.
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Acidified catchments are known to hold significantly reduced dipper Cinclus cinclus populations throughout the year relative to circum-neutral rivers, although the processes leading to these declines remain unclear. This study considered the population ecology of dippers within the circumneutral River Devon catchment, Central Scotland, and focused primarily on determining the factors influencing survival, breeding probabilities and reproductive success. It aimed to examine the role of spatial variation in 'habitat quality' on the population (and meta-population) dynamics of dippers, based on measures of seasonal and lifetime reproductive success, and the balance between survival and reproduction; in particular, to assess if the reduced reproductive success of dippers on acid rivers is likely to lead to population declines. Within the Devon catchment, approximately 81% of all adults survived from spring (March/April) to autumn (September/October), with 65% of these birds surviving from autumn to the following breeding season. Overall, these estimates predicted annual adult survival rates of c.53%, with no significant differences between years. Population density had no detectable effect on adult mortality rates, although juvenile over-winter survival was significantly lower than the adult rate at between 40 and 58%, and negatively related to the total size of the autumn population. There was no evidence of sex differences in juvenile over-winter survival, or any significant influence of weather or river flows on the rates for adults or juveniles. The local post-fledging survival of females was significantly lower than for males, however, apparently reflecting sex differences in post-natal dispersal. On average, less than 6.5% of all eggs laid, or 10.4-14.5% of male and 6.3-9.2% of female fledglings raised within the Devon catchment survived locally to breeding age. Juvenile, although not adult, recapture rates in spring were significantly lower than for birds known to have bred previously and negatively related to spring river flows. This suggested that with recapture dependent on a breeding attempt that was successful at least until laying, either more first year birds failed during the initial stages of nesting or that full breeding was not achieved at age one. The birds fledging the most young, both within a season and over a lifetime, all bred at 'prime' lowland sites characterised by wide, shallow rivers of intermediate gradient, although with less than 10% of all birds attempting to raise a second brood each year, no significant habitat differences were identified in any component of reproductive output measured until fledging. River width, altitude and gradient were all significantly inter-correlated and related to laying date, however, and post-fledging survival was significantly reduced for late fledged young. On average, lowland birds laid earlier than upland breeders, and were significantly more likely to produce autumn 'recruits' due to the enhanced post-fledging survival prospects of their young. This suggested that broad measures of river structure can provide a biologically appropriate classification of habitat quality. The size of the breeding population of dippers within the Devon catchment appeared to be related to the availability of critical resources, most likely food, roost sites and ultimately breeding territories through density-dependent changes in over-winter mortality and recruitment. The relative importance of resource abundance and recruitment levels in determining autumn population densities on acid streams still remained unclear, although reference to published relationships between acidity and reproductive success suggested that with adult survival at the rate estimated for the Devon catchment, many dipper populations are unlikely to produce sufficient recruits to match all adult losses, and may only persist with continued immigration from more productive (circumneutral) catchments elsewhere.
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Addison, BriAnne Ashley. "Maternally derived antibodies in avian eggs and offspring ecology, life history, and development /." Diss., St. Louis, Mo. : University of Missouri--St. Louis, 2009. http://etd.umsl.edu/r3961.
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Knowles, S. C. L. "Ecology and evolutionary significance of malaria in wild birds." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543017.
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Ko, Wai-ping Ice, and 高惠冰. "The nutritional ecology of frugivorous birds in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31238683.
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Spottiswoode, Claire N. "Behavioural ecology and tropical life-histories in African birds." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615302.
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Jenkins, Antoinette. "The evolutionary ecology of Leucocytozoon blood parasites of birds." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/4381.
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Parasites can impose fitness effects on host populations: there may be seasonal and geographic variation in the interaction as well as over a longer time scale, host-parasite cospeciation. I investigate the Leucocytozoa parasites of birds as a model system to try to understand the role of diversity of infection, dispersal and scale on the nature of the coevolutionary process between the hosts and parasites. Leucocytozoa had effects on the breeding success of a population of the blue tit, Cyanistes caeruleus. Number of infections was important, and old birds infected with mixed lineage infections raised broods of significantly lower quality than those infected by a single lineage or uninfected birds. There was also evidence for individual lineage effects. The parasites showed seasonal dynamics, and overall prevalence followed a model previously proposed for the dynamics of avian malaria. Individual lineages, however, displayed different dynamics; this emphasises the importance of consideration of lineage identity. These results may have consequences for the evolutionary dynamics of this host-parasite interaction. The geographic context of the Leucocytozoa-bird interaction was investigated, and little phylogeographic structuring was found in parasite lineages across Europe. Contrary to predictions, the distribution of individual lineages followed the abundance-occupancy relationship, suggestive of widespread dispersal. At a larger phylogenetic scale I looked for evidence of host-parasite cospeciation in this system. There was a strong signal of coevolution due to cospeciation in 40% of the host-parasite associations. Migrant hosts harboured significantly fewer cospeciating parasites than residents and partial migrants. The implications and potential applications of this type of cospeciation analysis are discussed. I conclude by suggesting that the bird-Leucocytozoon system is an excellent model system for the study of host-parasite interactions, attaining high diversity and prevalence in some cases. Furthermore, the role of diversity, mixed lineage infections and dispersal are key to our understanding of the evolutionary dynamics of this system.
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Mealey, Brian Keith. "Reproductive ecology of the burrowing owl, Athene cunicularia floridana, in Dade and Broward Counties, Florida." FIU Digital Commons, 1992. https://digitalcommons.fiu.edu/etd/3642.
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From 1988 to 1990 a study of the reproductive ecology of the burrowing owl was conducted to determine seasonality and reproductive success in Dade and Broward Counties. Reproductive data for each of the three years (1988- 1990) reveal a higher reproductive success rate (54%) for 1990 than 1989 (40%) and 1988 (40%). Owls using previously used burrows had a higher success in fledging young (63%) than newly excavated burrows (19%). T-tests were conducted on several appendage measurements of male and female owls to determine sexual dimorphic traits. Metatarsus lengths of males and females were different (t=2.36, p=0.02). As of 1990,197 owls had been banded in the study area. In 1989, 75% and in 1990, 83% of the banded adults were found on the same territory. Only 4 of 129 banded nestlings have been reencountered in the study sites.
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Jackson, Susan. "Seabird digestive physiology in relation to foraging ecology." Doctoral thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/21813.
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This study addresses the question: are seabirds digestive opportunists or specialists? The extent of specialization in seabird digestive processes to different diets and foraging methods, is investigated experimentally. Gut passage rates of different food types of tested in vitro digestibility may reflect dietary specialization, with favoured prey types excreted more rapidly than less frequently encountered prey. Mean retention times of solid digesta are significantly correlated with foraging trip duration, and with gut length. Gut length and volume in tum scale with body mass. Assimilation efficiencies of various dietary components are not predictable purely on the basis of food composition, and show a high degree of inter- and intraspecific variability. Energy assimilation efficiency does not reflect dietary specialization, and may be maintained at approximately 75% regardless of diet. Assimilation efficiency is, however, temporarily elevated in energetically-stressed birds, such as penguins that have recently completed moult. Digestive specializations are reflected in seabirds' abilities to assimilate substances specific to certain prey organisms. Unlike most terrestrial vertebrates, seabirds are able to digest wax esters, compounds important in marine food webs. Procellariiforms exhibit unique gastric adaptations facilitating extended foraging trips and efficient transport of food to their young, both important advantages for predators exploiting patchy and unpredictable food resources. Seabirds which naturally feed on crustaceans secrete the specific enzyme chitinase from their gastric mucosae, permitting digestion of the chitinous exoskeleton of the prey. The ability to secrete this enzyme is probably a retained ancestral trait rather than a newly evolved one, and may have been lost by seabirds that do not prey on crustaceans. Differences between penguins and procellarids reflect unique adaptations to the different foraging techniques employed by these two families. The synthesis of the thesis explores the adaptive significance of gut passage rate and allometry of the gut in relation to the two predominant foraging techniques employed by seabirds: long- distance aerial soaring and subsurface swimming. Scaling of seabird gut size may play an important role in the interplay between metabolic rate, the energy demands of foraging, and digestive physiology. The allometric approach taken here is potentially useful for studies of seabird digestion, and has application in studies linking the evolution of avian body size, and foraging ecology.
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Ausprey, Ian J. "Post-fledging Ecology of Two Songbird Species Across a Rural-to-Urban Landscape Gradient." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276811589.
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Briggs, Christopher W. "Survival and nesting ecology of the Swainson's hawk in Butte Valley, CA /." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447802.
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Thesis (M.S.)--University of Nevada, Reno, 2007."May, 2007." Includes bibliographical references. Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2007]. 1 microfilm reel ; 35 mm.
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Groot, Damon. "A deep dive into the Prinia atrogularis complex : A tale of birds and taxonomy." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-435486.
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The taxonomy of the taxa in the Prinia atrogularis-khasiana-superciliaris complex has changed several times in recent history. To this day, different world bird lists classify this complex as 1–3 species. These classifications are based mainly on morphological comparisons of museum specimens. No study has analysed the songs and genetics of this complex. This thesis focuses on the integrative taxonomy of this complex by analysing and comparing their song and mitochondrial cytochrome b (cytb) gene. Seventeen different variables from in total 172 individual songs were measured and analysed. A linear discriminant analysis showed a clear separation in song between atrogularis, khasiana and the superciliaris group (latter including the taxa superciliaris, erythropleura, klossi, dysancrita and waterstradti). The mitochondrial cytb phylogenetic tree produced using Bayesian inference suggested that atrogularis and khasiana split from superciliaris around 4.9 million years ago (mya), with atrogularis and khasiana splitting from each other around 3.4 mya. Based on the combined results of the song and cytb analysis I propose to recognise three species: Black-throated Prinia Prinia atrogularis, Rufous-crowned Prinia P. khasiana and Hill Prinia P. superciliaris. The study also showed some support for classifying klossi as a separate species, but acquisition of additional information is needed to verify this.
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Tompkins, Daniel Michael. "Evolutionary ecology of bird-parasite associations." Thesis, University of Oxford, 1996. http://ora.ox.ac.uk/objects/uuid:a5f5ea19-b799-490b-b738-99ff52df25c1.
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This thesis investigates the ecological determinants of chewing louse (Insecta: Phthiraptera) host-specificity on four species of Malaysian swiftlets (Aves: Apodidae). Influences of host coloniality on louse ecology were also demonstrated, illustrating the dependence which these permanent ectoparasites have on their hosts. Louse collections were made to look for incidences of host-specific lice occurring on the "wrong" host ("straggling"). Straggling was observed, implying that lice disperse among host species. Thus, opportunity for louse dispersal (or lack thereof) does not govern the host-specificity of chewing lice on swiftlets. Experimental transfers of lice between hosts were conducted. Louse survival was reduced on foreign host species. This implies adaptation to specific host characters, suggesting that specialisation governs chewing louse host-specificity on swiftlets. There was no evidence for reciprocal adaptation of swiftlets to their normal louse species. Lice had no impact on the fitness of either swiftlets or the related common swift. Furthermore, neither swiftlet nor swift lice were transmitting pathogenic endoparasites. This implies that chewing lice and Malaysian swiftlets have not "coevolved". Survival of transferred lice was determined by the relatedness of donor and recipient hosts. Closer related swiftlet species are more similar in body size and feather dimensions. When the feather dimensions of the microhabitat distributions of the same louse species on different hosts were compared the results suggested that lice keep the dimensions of barb and barbule diameter, at which they occur, "constant" through microhabitat shifts. This suggests that feather dimensions are the host characters which determine the survival (and host-specificity) of chewing lice on birds. The ability of chewing lice to survive on hosts with similar feather morphology implies that "host-switching", between distantly related hosts with similar morphological characters (due to parallel or convergent host evolution), may have been an important factor in the evolution of bird-louse associations.
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Ecklar, Brooke Irene. "Evaluating Migratory Stopover Success: Monitoring the Decline of Bird Populations at Hueston Woods Biological Station." Miami University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=miami1596196643385067.
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Slater, Steven J. "Wyoming's riparian bird communities issues of scale and human-caused vegetation and landscape change /." Laramie, Wyo. : University of Wyoming, 2006. http://proquest.umi.com/pqdweb?did=1212779261&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Zolkowski, Stephanie B. "Habitat relationships of bird communities in Wisconsin peatlands /." Link for full-text, 2008. http://epapers.uwsp.edu/thesis/2008/Zolkowski.pdf.
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Rolek, Brian William Hill Geoffrey E. "Microhabitat associations of wintering birds in a southeastern bottomland forest within the easter Gulf coastal plain of Florida." Auburn, Ala., 2009. http://hdl.handle.net/10415/1795.
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Baltz, Michael E. "The nonbreeding season ecology of neotropical migratory birds in the dry zone of Puerto Rico /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9988644.
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Bamford, Andrew J. "The ecology and conservation of scavenging birds in southern Africa." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.495539.
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Like many large raptors, vultures are intolerant of humans, making them difficult to study; consequently their ecology is not well understood. New technologies such as satellite tracking, and more powerful statistical analysis have the potential to reveal more about these birds. White-backed vultures display an aversion to nesting in proximity to humans, and, in areas with high human population densities, are restricted to nesting in nature reserves and private game farms; lappet-faced vultures display even less tolerance to human presence. Cape vultures, fitted with satellite tracking devices, showed a preference for foraging close to their nest or roost, but avoided areas of human settlement when foraging. White-backed vultures appear adaptable in their choice of nest site and can nest at high densities; they appear able to survive in small protected areas, but this is not true of other species. Habitat associations of vultures were not general across regions. Breeding success of vultures and marabou storks is apparently related to food availability. In the case of white-backed vultures nest success was also negatively affected by nesting density, but density did not affect the colonially nesting marabou or territorial lappet-faced vulture. Immature birds are capable of moving large distances after fledging: movements of over 1000km from the nest site were recorded by cape vultures and marabous. These results have implications for the continued survival of these species; their differing abilities to adapt to human presence will most likely affect those chances of survival.
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Robinson, Robert A. "The ecology and conservation of seed-eating birds on farmland." Thesis, University of East Anglia, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389198.
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1. Many species of bird breeding in Britain have declined in recent decades. However, only in the farmland ecosystem are the majority of species, primarily seed-eating passerines, declining. Similar declines in these species are also occurring elsewhere in Europe and North America. This thesis aims to model the effects of habitat change on population size ofthese species through an understanding of their behaviour. 2. A wide range of factors, primarily relating to the intensification of agricultural management, have been implicated in these declines, and these are reviewed in detail. There is little evidence for consistent impacts on the breeding biology, but considerable circumstantial evidence that declines in winter food supply have been a major cause of the declines. 3. Three species of seed-eating passerine are studied in detail, skylark Alauda arvensis, yellowhammer Emberiza citrinelia and com bunting Miliaria calandra. In winter, yellowhammers and com buntings used stubble fields exclusively; skylarks much preferred stubble fields. All avoided winter cereal fields. This is related to seed density, stubble fields held virtually all the cereal grain found in the soil and many more weed seeds than winter cereal fields. 4. The functional responses of skylarks, yellowhammers and com buntings are described. Seed availability plays an important role in determining intake rate, with seeds buried beneath the surface harder to obtain, particularly for yellowhammers. Seed availability has more general implications for the nature of functional responses. 5. Bird numbers were related to seed density, the aggregative response. The scale at which aggregative responses were observed varied between species. The availability of seeds in the soil column affected the birds use of fields, with the number of seeds on the surface important. The location of hedgerows was also important, yellowhammers and com buntings preferred to forage close to them, skylarks did not. 6. The general effects of overwinter mortality on population size are modelled and the effects of two causes of winter mortality, starvation and predation are analysed. Individuals traded-off these two risks which had an interactive effect on mortality. Density-dependence in the breeding season interacts with winter mortality to set population size. 7. The results presented in this thesis are used to model the effects of habitat changes on populations of seed-eating birds. The predicted population, on the basis of winter food supply, was close to the current actual population size. These models are used to assess the effectiveness of different management options, with unharvested conservation headlands being best for species such as the yellowhammer and tree sparrow Passer montanus, while set-aside is best for species such as the skylark.
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Smith, Nicoleen Celeste. "Birds and the urban ecology of Potchefstroom / Nicoleen Celeste Smith." Thesis, North-West University, 2004. http://hdl.handle.net/10394/593.
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Human activities cause drastic changes in the environment, such as the
fragmentation of habitats, which is the greatest threat to the world's
biodiversity and biogeography. By using birds to study habitat changes, it is
possible that the type of habitat qualities that may still be possible near and in
cities could be determined. It is possible that by improving the quality or
conditions of habitats for birds, habitat qualities for other fauna would also
improve. Birds are also considered to be good indicators as they are
collectively sensitive to changes in their environments; however, they are also
easy and relatively inexpensive to survey.
There is no single definition for an urban area, however, these are the places
where environmental problems greatly affect the quality of life. Urbanisation
is a continuous complex process and in order to understand the ecology of
urban areas, the reasons and factors behind this process need to be
understood. Cities themselves represent the extremes of human-modified
environments and usually only contain a few remnants of the original habitat.
On the other hand, many cities in South Africa are characterised by
secondary woodland, as trees and other plants are planted in gardens and
parks. This creates habitat that could be advantageous to birds. Biotopes
have been used to map this aspect of cities, and it has generally been
assumed that birds will distribute accordingly.
The hypothesis for this study was as follows: Due to the mobility of birds,
coupled with their ability to use multiple biotopes (e.g. nesting and feeding),
urban bird communities or bird demography will show patterns different from
vegetation and structure based biotopes alone, and could therefore be
considered as avitopes.
The primary aim of this study was to determine the distribution patterns of
avian diversity in Potchefstroom. Secondary aims/objectives for this study
included:
Determining the bird species distribution in Potchefstroom using point
counts
Determining the distribution of feeding and nesting guilds in
Potchefstroom
Determining whether it is possible to identify urban avian indicators
with this type of research
To investigate, develop and define the concept of "active-habitat
selectors" (AHS)
To introduce, develop and define the concept of "avitopes"
The research area included the city of Potchefstroom, with its associated
suburban areas, lkageng, Promosa, Mohadin, the rural areas and the
surrounding natural areas. Point counts were used to identify bird species at
56 different sites. The data was analysed using to two different programmes,
GS+ and Primer 5. The data was analysed according to species richness,
species abundance and numbers of birds.
I found that species were most abundant in the agricultural areas, the eastern
residential areas and the military areas. The socio-economic factors affecting
the abundance and distribution of all the species, still needs to be further
researched. When looking at the total avian biomass for this study, biomass
was highest in the industrial area, which is probably the most highly urbanised
site in the study area, due to the high numbers of doves and pigeons. The
results for species richness indicated that the greatest species richness
occurred in the less highly urbanised areas, and was lowest in the more highly
urbanised (industrial) areas. The lower half of the western part of lkageng
also had a low species richness, even though this is not a highly urbanised
area. However, it is possible that conditions in this area are highly unsuitable
for bird species due to various reasons such nesting availability, resource
availability, density of people etc.
When looking at the results for granivores, the majority of the species, and
more so their numbers, were found primarily in the urbanised areas, with
some present in the agricultural areas. However, this could possibly be put
down to the fact that the agricultural areas are primarily a foraging area. In
the case of omnivores, the highest numbers were found in the military areas
and included only a small part of the very top section of the residential areas.
The military areas are not highly urbanised areas. However, it is possible the
reason for their low occurrence in the more urbanised areas was due to the
insufficient 0bSeNati0n time, since omnivores were 0bSe~edin many of the
more urban areas whilst not sampling in those areas. Omnivores and
granivores are superior competitors when compared to other species, as they
are better able to exploit urban food resources.
In the case of the insectivores, the majority of them were located outside of
the more urbanised areas; however, a focal point did occur in the very
southern tip of the eastern residential areas. It is possible that they nest in
this part of the residential areas but forage in the nearby agricultural areas.
Birds were therefore not restricted to a single area or biotope, as they are able
to utilise various suitable areas for different purposes e.g. foraging, nesting
etc. Because of their mobility and ability to choose a suitable habitat, I have
introduced the concept of active-habitat-selectors (AHS) in this study. Various
elements support this idea, such as birds being able to choose a suitable
habitat through choice, rather than as an automatic response, and that birds
are able to continuously select habitats to support their needs etc. A
preliminary definition for AHS could be the following:
Active habitat selectors are those species of which the adult individuals
within their lifetime are almost continuously able to select multiple,
suitable habitats for different purposes, through choice, due to their
mobility and comparative knowledge of different available habitats that
are in range.
The concept of avitopes has also been introduced and various elements have
been taken into account with its definition. Some of these elements include,
birds are good indicators of environmental change, they are not restricted to
any single areas, etc. Various elements should be considered when defining
avitopes. A preliminary definition could be:
Avitopes are geographically delineated areas, defined by diversity
indices, and do not take into account non-naturally occurring, nonvagrant,
and otherwise generalist bird species.
There are still arguable aspects of these definitions, which will require more
development, refinement and research.
All the objectives for this study have been achieved and new issues identified,
that will require further investigation.Thesis (M. Environmental Sciences)--North-West University, Potchefstroom Campus, 2005.
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Bennett, P. M. "Comparative studies of morphology life history and ecology among birds." Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379453.
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Jacobs, Jennifer H. "The birds and the bees : pollination of fruit-bearing hedgerow plants and consequences for birds." Thesis, University of Stirling, 2008. http://hdl.handle.net/1893/1319.
Full textAbstract:
Hedgerow fruits provide a food resource for several UK farmland bird species from late summer, through winter and into spring. This project aims to develop the understanding of the interactions between fruit-bearing hedgerow flowers, their pollinators, hedgerow fruits and frugivorous birds. Experiments revealed that flowers of blackthorn, hawthorn and ivy all benefited from insect visits in order to develop fruit. The flowers of bramble and dog rose showed little requirement for insect pollination, and produced fruit when insects were excluded. There was evidence that for the hedges under study, the pollination service provided by insects to blackthorn and hawthorn flowers was inadequate since the flowers of these plants were pollen limited. The relative abundance of different insect groups foraging on blackthorn flowers was highly variable between hedges, suggesting that the contribution of a particular insect group to blackthorn pollination may vary according to their local density. Bumblebees, bristly flies and solitary bees were considered to have the greatest value for pollinating blackthorn flowers, based on foraging attributes (bumblebees and solitary bees), and abundance (bristly flies), but their activity did not correlate with the proportion of flowers that set fruit. Solitary bee activity correlated with hawthorn pollination, and there was strong evidence that social wasps were the best pollinators of ivy flowers on the hedges studied. Environmental factors such as hedge aspect did not significantly affect the activity of most pollinators (with the exception of solitary bees) or the proportion of blackthorn flowers that set fruit. Equally, the presence of the mass-flowering, attractive forage source, oilseed rape in fields adjacent to hedgerows, did not significantly influence the activity of most pollinators or the proportion of hawthorn flowers that set fruit. The abundance of some frugivorous birds, in particular the migratory thrushes (redwings and fieldfares) was positively related to the yield of fruits, including sloes and haws in hedges. So the evidence suggests that on these farms, pollinator communities are important for ensuring some hedgerow shrubs provide copious fruit, which may be vital for birds during winter months when invertebrate food is scarce. These links between flowers, pollinators, fruits and birds are discussed, alongside suggestions for safeguarding the fruit supply for farmland birds in the future.
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Håstad, Olle. "Plumage colours and the eye of the beholder : the ecology of colour and its perception in birds /." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3864.
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Hulme, Mark F. "The density and diversity of birds on farmland in West Africa." Thesis, St Andrews, 2007. http://hdl.handle.net/10023/424.
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Palmer, Grant Campbell, and grant palmer@deakin edu au. "Ecological value of riparian zones to birds in forest landscapes." Deakin University. School of Life and Environmental Sciences, 2007. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20071115.083927.
Full textAbstract:
Riparian zones are a characteristic component of many landscapes throughout the world and increasingly are valued as key areas for biodiversity conservation. Their importance for bird communities has been well recognised in semi-arid environments and in modified landscapes where there is a marked contrast between riparian and adjacent non-riparian vegetation. The value of riparian zones in largely intact landscapes with continuous vegetation cover is less well understood. This research examined the importance of riparian habitats for avifauna conservation by investigating the ecological interactions contributing to the pattern of bird assemblages in riparian and adjacent non-riparian habitats. Specifically, the focus is on the bird assemblages of riparian zones and those of adjacent non-riparian vegetation types and the influence that associated differences in resource availabilities, habitat structure and conditions have on observed patterns.
This study was conducted in the foothill forests of the Victorian Highlands, south-east Australia. Mixed-species eucalypt (genus Eucalyptus) forests dominate the vegetation of this region. Site selection was based on the occurrence of suitable riparian habitat interspersed within extensive, relatively undisturbed (i.e. no recent timber harvesting or fire events) forest mosaics. A series of 30 paired riparian and non-riparian sites were established among six stream systems in three forest areas (Bunyip State Park, Kinglake National Park and Marysville State Forest). Riparian sites were positioned alongside the stream and the non-riparian partner site was positioned on a facing slope at a distance of approximately 750 m. Bird surveys were carried out during 29 visits to each site between July 2001 and December 2002.
Riparian sites were floristically distinct from non-riparian sites and had a more complex vegetation structure, including a mid-storey tree layer mostly absent from non-riparian sites, extensive fine litter and coarse woody debris, and dense ground-layer vegetation
(e.g. sedges and ground ferns). The characteristic features of non-riparian habitats included a relatively dense canopy cover, a ground layer dominated by grasses and fine litter, and a high density of canopy-forming trees in the smaller size-classes.
Riparian zones supported a significantly greater species richness, abundance and
diversity of birds when compared to non-riparian habitats. The composition of bird assemblages differed significantly between riparian and non-riparian habitats, with riparian assemblages displaying a higher level of similarity among sites. The strongest contributors to observed dissimilarities between habitat types included species that occurred exclusively in either habitat type or species with large contrasts in abundance between habitat types. Much of the avifauna (36%) of the study area is composed of species that are common and widespread in south-east Australia (i.e. forest generalists). Riparian habitats were characterised by a suite of species more typical of wetter forest types in south-east Australia and many of these species had a restricted distribution in the forest mosaic. Some species (7%) occurred exclusively in riparian habitats (i.e. riparian selective species) while others (43%) were strongly linked to these habitats (i.e. riparian associated species). A smaller proportion of species occurred exclusively (2%) in non-riparian habitats (i.e. non-riparian selective species) or were strongly linked to these habitats (10%; i.e. non-riparian associated species).
To examine the seasonal dynamics of assemblages, the variation through time in species richness, abundance and composition was compared between riparian and non-riparian sites. Riparian assemblages supported greater richness and abundance, and displayed less variation in these parameters, than non-riparian assemblages at all times. The species composition of riparian assemblages was distinct from non-riparian assemblages throughout the annual cycle. An influx of seasonal migrants elevated species richness and abundance in the forest landscape during spring and summer. The large-scale movement pattern (e.g. coastal migrant, inland migrant) adopted by migrating species was associated with their preference for riparian or non-riparian habitats in the landscape. Species which migrate north-south along the east coast of mainland Australia (i.e. coastal migrants) used riparian zones disproportionately; eight of eleven species were riparian associated species. Species which migrate north-south through inland Australia (i.e. inland migrants) were mostly associated with non-riparian habitats. The significant differences in the dynamics of community structure between riparian and non-riparian assemblages shows that there is a disproportionate use of riparian zones across the landscape and that they provide higher quality habitat for birds throughout the annual cycle.
To examine the ecological mechanisms by which riparian assemblages are richer and
support more individual birds, the number of ecological groups (foraging, nest-type and body mass groups) represented, and the species richness of these groups, was compared between riparian and non-riparian assemblages. The structurally complex vegetation and distinctive habitat features (e.g. aquatic environments, damp sheltered litter) provided in the riparian zone, resulted in the consistent addition of ecological groups to riparian assemblages (e.g. sheltered ground invertebrates foraging group) compared with non-riparian assemblages. Greater species richness was accommodated in most foraging, nest-type and body mass groups in riparian than non-riparian assemblages. Riparian zones facilitated greater richness within ecological groups by providing conditions (i.e. more types of resources and greater abundance of resources) that promoted ecological segregation between ecologically similar species. For a set of commonly observed species, significant differences in their use of structural features, substrates and heights were registered between riparian and non-riparian habitats.
The availability and dynamics of resources in riparian and non-riparian habitats were examined to determine if there is differential availability of particular resources, or in their temporal availability, throughout the annual cycle. Riparian zones supported more abundant and temporally reliable eucalypt flowering (i.e. nectar) than non-riparian habitats throughout the annual cycle. Riparian zones also supported an extensive loose bark resource (an important microhabitat for invertebrates) including more peeling bark and hanging bark throughout the year than at non-riparian sites. The productivity of eucalypts differed between habitat types, being higher in riparian zones at most times for all eucalypts combined, and for some species (e.g. Narrow-leaved Peppermint Eucalyptus radiata). Non-riparian habitats provided an abundant nectar resource (i.e. shrub flowering) at particular periods in the annual cycle. Birds showed clear relationships with the availability of specific food (i.e. nectar) and foraging resources
(i.e. loose bark). The demonstration of a greater abundance of resources and higher primary productivity in riparian zones is consistent with the hypothesis that these linear strips that occupy only a small proportion of the landscape have a disproportionately high value for birds.
Riparian zones in continuous eucalypt forest provide high quality habitats that contribute to the diversity of habitats and resources available to birds in the forest
mosaic, with positive benefits for the landscape-level species pool. Despite riparian and non-riparian habitat supporting distinct assemblages of birds, strong linkages are maintained along the riparian-upslope gradient. Clearly, the maintenance of diverse and sustainable assemblages of birds in forest landscapes depends on complementary management of both riparian and non-riparian vegetation.
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Phillips, Richard A. "Population ecology of Arctic skuas Stercorarius parasiticus, on Foula." Thesis, University of Glasgow, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294176.
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Line, Eric R. "Effects of Landscape Aggregation and Landscape Conversion on Bird Diversity in Ohio from 2013-2017." Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1621604319860423.
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Roades, Heather Nicole. "Species Composition, Relative Abundance, and Habitat Occurrence of Neotropical Migratory Birds Overwintering in Dominica, West Indies." Miami University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=miami1343956255.
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