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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Birds in the City : Bird biodiversity in a boreal northern urban environment

Eriksson Reuterborg, Izabel January 2022 (has links)
Urbanization is a growing threat to biodiversity across the globe. As more and more habitats are being destroyed and species extinction rates are rising, we have started looking at how we might decrease this loss of biodiversity. One answer is changing our urban environments to more biodiversity friendly ones. Since conditions within a city and a natural landscape might differ, it is important to understand how landscape variables affect biodiversity in urban areas. The purpose of this study was to investigate how landscape variables (Coniferous/mixed forest, Open uncultivated land, Fields, Deciduous forest, Water, High and Low urban development, and Industrial area) affect bird diversity, richness, and community assembly in a small city in central Sweden. Surveys were conducted on 33 sites. Results from a multiple regression comparing the environmental variables to richness or diversity showed that Water was positively correlated to both diversity and richness. A redundancy analysis (RDA) showed that bird species assemblage was significantly affected by Coniferous/mixed forest, Water, and Fields when the whole bird community was considered. However, when only passerines were included in the RDA, Urban development and Coniferous/mixed forest had the strongest impact. When conservation efforts are made in urban areas, these variables need to be considered since they are correlated with different species and they might not be the same ones that are associated with richness or diversity of birds.
2

The Conservation Value of Residential Landscapes for Native Bird Communities: Patterns, Processes, and Management Implications

Lerman, Susannah Beth 01 September 2011 (has links)
Urbanization, as it transforms natural biotic systems into human-dominated landscapes, is recognized as one of the greatest threats to biodiversity throughout the world. Furthermore, urban dwellers are becoming increasingly disconnected with the natural world. Here I investigate whether residential landscape designs that mimic the natural environment can provide habitat for native birds. First I uncover some of the patterns of bird distribution in residential yards by incorporating habitat features, urbanization measurements and socioeconomic factors with bird monitoring data into a multivariate analysis. The results indicate that native birds associate with neighborhoods with native plants and shrubs, neighborhoods closer to desert tracts, and higher income neighborhoods. Very few bird species associate with low income and predominantly Hispanic neighborhoods. Additional analyses based on social survey data demonstrate that residents notice the varying levels of bird variety in their neighborhood. Second, I address whether perceived habitat quality differs between residential landscape designs by testing foraging decisions at artificial food patches. Birds foraging in yards landscaped with native plants consume fewer resources than birds foraging in exotic landscaped yards. This suggests that alternative food sources are more available in the native landscaped yards, indicating better quality habitat. Third, I investigate the relationship between native bird diversity and neighborhoods with a Homeowner Association (HOA). Neighborhoods with an HOA have higher native bird diversity, perhaps due to an active and enforceable landscape maintenance plan. I suggest an HOA adapt features from the Sustainable Sites Initiative to further improve habitat conditions for native birds and other wildlife. Results from the Dissertation support the implementation of native landscaping in residential yards to help reverse the loss of urban biodiversity. Consequentially, these landscapes will provide positive opportunities for urban dwellers to reconnect with the natural world.
3

A Integrative Investigation of Urban Animals and the Ecosystem Services They Provide in Cities

Swartz, Timothy, 0000-0001-7248-2473 08 1900 (has links)
Urban landscapes are complex social-ecological systems comprising human and natural elements and their interactions. A key priority for research in these landscapes is understanding how humans affect the presence and abundance of wild organisms and how those organisms, in turn, provide ecosystem services that affect humans. In this dissertation, I use two field studies to understand the ecosystem services provided by urban animals in green spaces across Philadelphia and in a third study I investigate geographic bias in where urban animals have been studied in the United States. For the first study, I use a functional trait approach to examine how urban bird communities respond to landscape- and local-scale habitat and how community composition corresponds to potential ecosystem services. I show that the landscape-scale context of a green space has a stronger influence on species’ abundances than local-scale habitat. As a result, the effect traits associated with cultural and regulating ecosystem services varied strongly along the landscape-scale gradient of urbanization. Local-scale variation in habitat had little effect. The importance of landscape-scale habitat in driving the supply of bird-mediated ecosystem services underscores the importance of regional urban planning for green spaces.In the second study, I use a field experiment to determine the drivers of an understudied ecosystem service – the removal of littered food waste by birds and squirrels. I recorded food removal activity by animals in green spaces across Philadelphia and found that Eastern gray squirrels (Sciurus carolinensis) are the main driver of this service. With increased squirrel abundance, removal level is higher and is both initiated and completed more quickly. This service is also context dependent, such that more food is removed in urban parks and picnic areas, where animals are presumably accustomed to consuming anthropogenic foods. These results highlight the importance of animal behavior, and factors that affect it, for the supply of ecosystem services. In my third study, I take a geographic approach to identifying bias in the study of animals in urban landscapes. Our knowledge of urban ecosystems in the United States is based on hundreds of field studies and thousands of individual field sites, but the distribution of these sites has never been examined. I reviewed the literature and mapped field sites to assess geographic bias in the location of urban ecology field sites. At a national scale, I find that urban ecologists tend to work in larger cities, especially those that are less socioeconomically vulnerable (more affluent). I also find that the social-ecological attributes of the neighborhoods in which ecologists work depends on the framing of their study as well as the focal taxa and functional groups studied. Overall, the neighborhoods where marginalized people live are an underexplored segment of the urban landscape. This is the first study to identify geographic biases in urban ecology field sites and provides a basis for future urban ecology research that produces knowledge applicable to all cities and neighborhoods. / Biology
4

Synanthropy of the Australian Magpie: A Comparison of Populations in Rural and Suburban Areas of Southeast Queensland, Australia

Rollinson, Daniel J., n/a January 2004 (has links)
The urbanised environment provides ecologists with unique situations in which to undertake ecological study. It has been said that urbanisation is like a natural experiment; we often have populations of animals that have gone from living in natural or semi-natural environments to living in a highly modified anthropogenic environment. These situations provide ideal settings to study the ecological and behavioural differences that may develop in populations located in different habitats. Urbanisation typically results in a minority of species dominating the fauna, and this thesis aimed to examine one such species, the Australian magpie. Despite the magpie being a common and well-liked suburban bird, the majority of previous research on this species has been undertaken within rural or exurban locations. This thesis aimed to examine what actually happens to the species when it lives in the suburban environment. In particular I focused on specific behavioural and ecological features, to see if there were any particular adaptations the suburban magpies showed and also if the suburban habitats provide certain resources favourable to the magpies and what ecological effects these may have. Comparisons of the territory structure and resources of rural and suburban magpies showed that although many features of the territory are similar between rural and suburban locations, notably the choice of native nest trees, magpie territories within suburban areas were smaller and contained more anthropogenic features. The reduced territory size may possibly be related to a greater abundance of key food resources also evident within suburban areas. Furthermore, suburban magpies are more successful in their foraging attempts, again possibly reflecting a more abundant food supply in suburbia and also the simplified nature of suburban foraging areas might facilitate more successful foraging. The increased foraging success is likely to explain the greater provisioning rate to nestling suburban magpies. Suburban magpies also utilised human provided foods. I quantified the extent of wildlife feeding within many of the suburban study sites of this thesis (through the use of questionnaire surveys). In each of the locations it was evident that at least one person (usually more) was providing a regular supply of food to wildlife and magpies appeared to be the main recipients of this food. Previous ecological studies suggest the provision of extra food to avian populations is likely to affect the breeding ecology, and this was so for magpies. The suburban populations initiated breeding significantly earlier than rural magpies. To test the influence of food, supplementary food was provided to rural magpies, not currently receiving any additional human provided foods. The fed rural magpies initiated breeding before control rural magpies (i.e. not receiving any additional food) but suburban magpies still initiated breeding before all other groups. This suggests additional factors present within suburbia, such as warmer temperatures, may also control the timing of breeding in magpies. Magpies in rural and suburban locations lived within different vertebrate communities. Within suburban magpie territories a greater number of intrusions were made by domestic animals, notably dogs (Canis lupus) and cats (Felis domesticus). The frequency of raptors entering the territorial areas occupied by magpies appears to suggest such events are more common in rural areas. The number of humans entering magpie territories was obviously greater in the more populated suburban areas and the majority of magpies responded neutrally to humans. However a group of magpies that previously exhibited extreme aggression towards humans were found to have a greater frequency of aggressive interactions with potential predatory intruders, which were primarily humans. Subsequent examination of the level of corticosterone from this aggressive group of magpies found that a high level of aggressive interactions with potential predators and humans is reflected in higher level of corticosterone, which may have implications for further behavioural and even physiological changes. An ability to habituate to human in urbanised areas is a key attribute of successful synanthropic species. Comparisons of magpies disturbance distances at different points along the urban gradient (the gradient that runs from the urbaised city to natural wildlands) found suburban magpies only responded to humans when they had approached to a close distance (often less than one metre) and many simply walked away to avoid the approaching human. Rural and exurban magpies responded to humans at greater distances than suburban magpies. The distance at which they responded to the human was usually 100 meters plus, and these magpies always flew away. A continuation of this investigation over a temporal scale again found the large difference in response to humans, with suburban magpies exhibiting a decreased response towards humans. However, a certain proportion of responses from suburban magpies were also aggressive. The examination of disturbance distance over the breeding season found that in suburban magpies the responses of most disturbance distance variables remained similar between breeding stages. Rural magpies, however, exhibited variation in their responses towards humans depending on the stage of breeding. It is suggested that the response of rural magpies may be a typical fear response towards an unusual potential threat. The studies presented in this thesis show that magpies have the behavioural capacity to take advantage of resources in suburban landscapes that are not available or are in lessor supply in rural landscapes, it is these abilities that facilitate the magpies synanthropy.
5

Optimising urban green networks in Taipei City : linking ecological and social functions in urban green space systems

Shih, Wan-Yu January 2010 (has links)
With the global population becoming more urban and less rural, increasingly research has argued for concepts such as establish Green Infrastructure (GI) as a tool for enhancing wildlife survival and human’s living quality (e.g. Harrison et al., 1995; Benedict and McMahon, 2006). However, an interdisciplinary planning approach underpinned by ecological and social evidence has not yet been fully developed. This research therefore seeks to integrate an ecological network with a green space planning standard by exploring the use of biotope and sociotope mapping methods. Seeking a comprehensive planning that takes all green resources into account, a green space typology is firstly developed according to Taiwanese contexts for identifying green spaces from land use maps. In order to specify effective features of these green spaces to bird survival and user preferences, an insight was conducted into the relationship of ‘birds and urban habitats’, as well as ‘human preferred urban green spaces’ in Taipei City. Important environmental factors influencing bird distribution and influencing human experiences in urban green spaces are respectively specified and developed into an ecological value index (EVI) to detail potential habitats and a social value index (SVI) to evaluate recreational green space provision. Interestingly, proximity to green space appears to plays a more critical role in human preferences than bird survival in Taipei city; size is important both as a habitat and for creating an attractive green space; and green space quality tends to be a more significant factor than its structure for both wildlife and people. Utilising the bio-sociotope maps, this thesis argues for a number of strategies: conserving, enlarging, or creating large green spaces in green space deficient areas; increasing ecological and recreational value by enhancing green space quality of specific characteristics; and tackling gravity distance by combining green space accessibility and attractiveness in optimising urban green structure. As these suggestions are a challenge to apply in intensively developed urban areas, barriers from land use, political mechanisms, technical shortages, and cultural characteristics are also explored with possible resolutions presented for facilitating implementation. It is clear that optimising a multifunctional GI for both wildlife and people requires interdisciplinary knowledge and cooperation from various fields. The EVI and SVI developed within this thesis create the potential for a more place-specific and quantifiable green spaces strategy to help better link ecological and social functions in urban areas.

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