• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 41
  • 4
  • 2
  • 2
  • 1
  • Tagged with
  • 61
  • 61
  • 13
  • 8
  • 7
  • 6
  • 5
  • 5
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 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.
41

Tritrophic interactions in forests direct and indirect interactions between birds, insect herbivores, and oaks /

Barber, Nicholas A. January 2009 (has links)
2 spread sheets included. Title from title page of PDF (University of Missouri--St. Louis, viewed February 8, 2010). Includes bibliographical references.
42

The biogeography of forest birds in the Limpopo Province, South Africa.

Forbes, Dale. 28 November 2013 (has links)
Forest assemblage composition is determined by local ecological (e.g. patch area, species interactions), landscape (e.g. patch connectivity) and regional (e.g. historical change in forest distribution) processes. I investigated the relative effect of these processes on bird and frog assemblage composition in two isolated archipelagos of Afrotemperate forest in the Limpopo Province. The linear relationship between local and regional species diversity suggests that forest bird assemblages in the Limpopo Province are unsaturated. In addition, 66% of bird species and 42% of frog species in southern African forests are generalist species (i.e., forest associated as opposed to forest dependent), suggesting that matrix species have invaded forest assemblages. I thus argue that forest bird and frog assemblage composition is primarily determined by regional (historical) processes and that local ecological processes play a relatively minor role. Forests in the Limpopo Province were eliminated by major climatic changes during the Quaternary with major forest expansion only in the last 6000 years. Limpopo Province forest assemblages have thus established fairly recently. No forest dependent frogs and one forest dependent bird have established in the Limpopo Province forests from the relatively proximate forests in eastern Zimbabwe. This suggests that the Limpopo River catchment has acted as a significant barrier to the dispersal of forest vertebrate faunas. Cluster analyses showed that the forest bird and frog assemblages are essentially Afrotemperate and South African in origin with all forest dependent frogs and 97% of forest dependent birds occurring in the KwaZulu-Natal scarp forests. In addition the most important environmental gradient of change in the southern African forest bird faunas was the geographical distance from northern KwaZulu-Natal. This gradient is congruent with a major northward radiation of faunas from the KwaZulu-Natal scarp into the Limpopo Province. As a result the Limpopo Province forests have low biodiversity values compared to the KwaZulu-Natal scarp because forest frog and bird faunas are largely derived from the latter region. However, the importance of the Limpopo Province forests lies in their protection of threatened vertebrates as well as in providing landscape heterogeneity and ecological services to the surrounding matrix. Soutpansberg forest bird assemblages appear to be more robust and resilient and comprise a significantly greater proportion of forest associated species than those of the Limpopo Province Drakensberg. This is likely to be a consequence of more severe climatic extinction filtering of these faunas caused primarily by the proximity of the Soutpansberg forests to the arid Limpopo valley during the development of these forests. Consequently, regional and historical processes have played a relatively greater role in determining forest bird assemblages in the Soutpansberg than in the Limpopo Province Drakensberg and species richness in the former region was not significantly affected by local ecological processes (including forest area, isolation and habitat heterogeneity). Forest area and habitat heterogeneity did, however, affect forest bird species richness and abundance in the Limpopo Province Drakensberg where the relatively lower importance of regional processes (compared to the Soutpansberg) has combined with anthropogenic disturbance of smaller forests to increase the influence of local ecological processes. However, the role of local processes in determining local species richness is likely to increase in both archipelagos if the current rates of anthropogenic change and disturbance to forests are sustained. Forests greater than 138 ha (minimum critical patch size) are needed to avoid an island effect on bird species richness in the Limpopo Province Drakensberg. However, the long-term conservation of vertebrate assemblages in Limpopo province forests depends upon the successful conservation of evolutionary and landscape processes. This can best be achieved by maximising forest connectivity and landscape heterogeneity through the protection of both riparian corridors and forests of all sizes. The maintenance of historical dispersal routes, in particular connectivity along the escarpment with the scarp forests of KwaZulu-Natal, is important. This would require the protection of forests on the KwaZulu-Natal scarp and along the entire northern Drakensberg escarpment. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.
43

Community composition and influence of forest structure on birds in the Evergreen State College forest reserve

Rehm-Lorber, Jora. January 1900 (has links) (PDF)
Thesis (M.E.S.)--Evergreen State College, 2009. / "March, 2009." Title from title screen (viewed 4/8/2010). Includes bibliographical references.
44

Anti-brood parasite defenses and nest-site selection by forest-edge songbirds in Central Missouri /

Burhans, Dirk E., January 1996 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.
45

Anti-brood parasite defenses and nest-site selection by forest-edge songbirds in Central Missouri

Burhans, Dirk E., January 1996 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.
46

Relative abundances of birds of prey in different forest habitats in the Western Newfoundland Model Forest /

Gosse, John W., January 1997 (has links)
Thesis (M. Sc.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 44-51.
47

Avifauna de matas ciliares do Rio Batalha e adjacências, região centro-oeste do estado de São Paulo, Brasil

Lucindo, Anderson da Silva 09 March 2011 (has links)
Made available in DSpace on 2016-06-02T19:31:55Z (GMT). No. of bitstreams: 1 3702.pdf: 4025151 bytes, checksum: 2e413c751a3db69e16a3736b9236c225 (MD5) Previous issue date: 2011-03-09 / Financiadora de Estudos e Projetos / Forest fragmentation and habitat loss in tropical regions are implicated for different organisms responses, with special attention to avian species susceptible to disturbance. They react negatively in the face of changes in their habitats, reducing population size. In this scenario, the riparian forests play an important role as refuge for many species of birds. This study aimed to survey the avifauna of two riparian forests belonging to the Batalha River, West-central region of the state of São Paulo. The birds were described according to their composition, guild structures, degree of dependence on forest quality and level of sensitively to disturbances. Altogether, the census methods applied across the paths and point counts revealed a total of 162 bird species distributed in 48 families and 21 orders, among which 98 were forests, 14 endemic to other kind of vegetation, 3 endangered, 8 near threatened 32 abundant residents and various insectivorous specialists. These results testify the important contribution of riparian forests of west-central of São Paulo state in the conservation of local birds that are sensitive to the fragmentation. / Fragmentação florestal e perda de hábitat em regiões tropicais têm suscitado diferentes respostas em diferentes organismos, com especial atenção às espécies sensíveis a perturbações e dependentes de florestas. Estas reagem negativamente frente às alterações em seus hábitats, reduzindo em tamanho populacional. Neste cenário as matas ciliares exercem importante papel como refúgio para diversas espécies de aves. O presente estudo teve por objetivos inventariar as aves de dois fragmentos ciliares pertencentes ao Rio Batalha, região centro-oeste paulista. A avifauna foi caracterizada quanto à sua composição e estrutura, bem como em relação à ocorrência de espécies dependentes e semi-dependentes de florestas, as quais respondem mais sensivelmente a perturbações em seus hábitats. O censo quali-quantitativo, aplicado através dos métodos de trajetos e de pontos de escuta, revelou uma riqueza de 162 espécies de aves somando a avifauna de ambas as áreas, distribuídas em 48 famílias e 21 ordens. Foram identificadas 98 espécies florestais, sendo 27 migratórias, 14 endêmicas a outras formações, 3 ameaçadas de extinção, 8 quase ameaçadas, 32 residentes abundantes e várias insetívoras e frugívoras especialistas. Esses resultados são suficientes para demonstrar a relevante contribuição de matas ciliares do Rio Batalha na conservação da avifauna regional, sensível ao processo de fragmentação. Palavras-chave:, guildas tróficas. 2
48

Phylogenetics and speciation of African Bradypterus and the Apalis thoracica complex

Solms, Lisel Esme 05 September 2005 (has links)
Presented in this thesis is the mitochondrial DNA (mtDNA) cytochrome b gene analysis of the phylogenetic relationships within the Apalis thoracica complex (600bp) as well as among selected African Bradypterus species (603bp). Within A. thoracica 28 individuals from 20 subspecies were analysed. There was only molecular support for 13 historically isolated clades as opposed to the 21 subspecies recognized based on morphology. Among these molecularly defmed clades were clades lynesi, juscigularis and flavigularis, all three of which are of conservation concern and were previously treated as species by some based on their distinct morphology. Molecular clock dating estimated the clades to be of Pliocene age, whereas genetic differentiation within clades was of Plio-Pleistocene to Pleistocene age. This result is consistent with that of other African montane birds. Under the phylogenetic species concept all 11 clades could be recognised as species although a multifaceted approach to species recognition which will include vocalisation data is suggested. Contrary to expectation, the isolated East African clades did not exhibit more variation than the continuously distributed clades within southern Africa. In fact, significant phylogeographic breaks were identified within South Africa that need further investigation. For the African Bradypterus, 13 individuals from six of the 10 African species were analysed. These species were not monophyletic. Based on sequence divergence B. victorini was as different from the other members of the genus as it was from the out groups. In addition its song is very distinct and both males and females sing. Therefore, based on the molecular results presented in this thesis as well as vocalisation data and, it is proposed that B. victorini is not a Bradypterus. This result is particularly significant in light of the growing evidence that the Cape region acted as a repository for ancient animal taxa and holds implications for the conservation status of the region. The molecular data supported the classification of the taxa based on habitat and song but in addition clarified the placement of B. victorini and B. sylvaticus. The basal position of the latter among the remaining members of the genus indicates that Bradypterus is primarily a forest taxon that radiated into other habitats. It must however be kept in mind that the current dataset is based on six of the 10 African Bradypterus and none of the Asian species. The possibility of hybridisation between B. sylvaticus and B. barratti was raised and needs to be tested through additional sampling. / Dissertation (MSc (Genetics))--University of Pretoria, 2006. / Genetics / unrestricted
49

Habitat Use, Productivity, and Fruit Selection of Birds in Early-Successional Habitats in Western Massachusetts

Labbe, Michelle A 01 January 2011 (has links) (PDF)
Early-successional habitats have become rare in much of the eastern United States, largely due to landuse change, forest maturation and the disruption of natural disturbance regimes. In addition to providing nesting habitat for shrubland species of high conservation concern, wildlife openings may be an important habitat for mature-forest birds during the postfledging period – a critical phase in the avian lifecycle with the potential for high mortality. The habitat requirements of birds during this time period are poorly understood. In this study I examined the relationship between habitat and landscape characteristics on; 1) the abundance of forest nesting birds in shrubland habitat during the postfledging season, and 2) the reproductive success of shrubland bird species. And lastly, I also examined the relationship between avian body condition and seed dispersal, with a focus on comparing native and invasive species. I found that the abundance of forest birds was strongly influenced by landscape characteristics, as well as food abundance and structurally complex vegetation. Shrubland birds varied in their response to habitat variables, but overall productivity was positively related to taller vegetation structure, and was negatively related to lower-dense vegetation. Frugivore diets were generalized, yet they selected native fruit more often than invasive fruit, and invasive fruit negatively affected condition. My findings are consistent with the results of previous studies of habitat use among postfledging birds, and suggest that, like for forest birds, habitat requirements for shrubland birds during the postfledging period differ from those during the nesting season. Hopefully these results will encourage other studies of this important, but poorly understood stage of the avian lifecycle.
50

Greenspace Conservation Planning Framework for Urban Regions Based on a Forest Bird-Habitat Relationship Study and the Resilience Thinking

Kato, Sadahisa 01 May 2010 (has links)
The research involves first conducting a "case study" of ecological data and applying the results, together with the resilience concept, to the development of a greenspace conservation planning framework for urban regions. The first part of the research investigates the relationship between forest bird abundance and the surrounding landscape characteristics, especially, forest area and its spatial configuration in urban regions at multiple scales. The results are similar for simple and multiple regression analyses across three scales. The percentage of forest cover in a landscape is positively correlated with bird abundance with some thresholds. Overall, the percentage of forest cover in the landscape, contrast-weighted forest edge density, and the similarity of land cover types to forest cover are identified as important for the conservation of the target bird species. The study points to the importance of species-specific habitat requirements even for species with similar life history traits and of maintaining some forest edges and/or edge contrast. The second part of the research involves the development of a landscape planning meta-model and its conceptual application to greenspace conservation planning, integrating the results of the first part. Administrative and planning units are recognized to exist in a nested hierarchy of neighborhood, city, and urban region, just as biodiversity can be conceived in a nested hierarchical organization of genes, populations/species, communities/ecosystems, and landscapes. Resilience thinking, especially the panarchy concept, provides a scientific basis and a metaphorical framework to develop the meta-model, integrating a proposed landscape planning "best practice" model at each planning scale. Ecological concepts such as response and functional diversity, redundancy, and connectivity across scales are identified as key concepts for conserving and increasing biodiversity and the resilience of an urban region. These concepts are then used in the meta-model to develop the greenspace conservation planning framework. Ecological processes such as pollination and dispersal, as well as social memory and bottom-up social movements---small changes collectively making a large impact at the broader scales as well as these incremental changes gaining momentum as they cascade across scales---are identified as cross-scale processes and dynamics that connect various planning scales in the meta-model.

Page generated in 0.0831 seconds