Global land-use change and industrialisation has driven biodiversity declines and impaired ecosystem functioning. Recently, there have been large-scale efforts to not only halt habitat loss but create and restore habitat on formerly managed (e.g. agricultural) land. However, although the effects of habitat loss and fragmentation on biodiversity are well understood, our understanding of how biodiversity responds to habitat created in a patchy configuration is not. In particular, little is known about the relative importance of local (e.g. patch size) vs landscape scales (e.g. amount of habitat in the landscape) for restoring biodiversity in created habitat. Here, a long-term, large-scale natural experiment (the Woodland Creation and Ecological Networks project) was used to understand how bird species, communities and behaviour respond to woodland created in a patchy configuration on post-agricultural land. I used a combination of direct and indirect survey methods to quantify bird diversity, abundance and vocal behaviour in post-agricultural woodlands of known age in Great Britain. I show that secondary woodlands favour generalist species and older patches contain more individuals and species due to their vegetation structure. In relative terms, local-scale factors such as patch size made the greatest contribution to bird diversity and abundance. Colonisation events drive community assembly in new habitat, and I found that large-scale (km2) habitat patterns were more important than patch-level factors during colonisation of breeding territories by a long distance migrant bird (Willow Warbler Phylloscopus trochilus). Land management practices surrounding a habitat patch can also affect its perceived quality and relative attractiveness to potential colonisers. Using the Eurasian Wren Troglodytes troglodytes as a model species, I found that high proportions of agricultural land at woodland edges caused an increase in perceived predation risk. In conclusion, I suggest that post-agricultural woodlands rapidly provide valuable habitat for generalist woodland birds. Local, patch-level factors (area, vegetation structure) also appear relatively more important than landscape factors for woodland bird communities. Land-managers seeking to maximise the benefits of woodland creation for birds should thus focus on creating large patches with a diverse vegetation structure.

Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2005. / Benthic macroinvertebrates (sampled using South African Scoring System, SASS5) and adult male Odonata (sampled with close-focus binoculars) were recorded on two streams and a river of Soutpansberg, with the aim of determining the effect of invasion and removal of alien riparian vegetation on their assemblages. A secondary aim was to establish the importance of dragonflies as indicators of degree of disturbance in rivers. Forty two aquatic macroinvertebrate families and 33 adult Odonata species were recorded at a total of 71 sampling units. Three distinct riparian vegetation types were selected (natural, alien and cleared). Cleared vegetation refers to clearing of invasive alien trees, allowing regrowth of natural vegetation. Natural and cleared vegetation supported more benthic macroinvertebrate families compared to alien vegetation. Certain families that were lost to alien vegetation were recorded from natural vegetation. The highest SASS5 score was recorded from natural vegetation, followed by cleared vegetation, and the lowest was from alien vegetation. The highest number of adult Odonata was recorded at cleared vegetation, with alien and natural vegetation supporting the least number of Odonata species. Vegetation type, stream flow and microhabitats were statistically identified as the most influential variables for benthic macroinvertebrate assemblages. For adult Odonata assemblages, vegetation type, shade and temperature were the most important environmental variables. Species assemblages of adult Odonata can be used as indicators of environmental condition of rivers. The clearing of alien riparian vegetation clearly benefits the indigenous benthic macroinvertebrates as conditions are restored to their natural state. It also benefits dragonfly species richness, but if natural succession proceeds to a shaded tree canopy, the effect becomes similar to that of habitat shaded by alien vegetation. The impact of alien vegetation is to reduce sun-loving invertebrate species, especially dragonflies, with lesser impact on shade-loving species.

Call number: LD2668 .T4 1985 G87 / Master of Science

Declines in breeding populations of most migrants across much of the Palearctic have been linked to environmental conditions in their African non-breeding grounds. Studying winter distribution dynamics for these species is necessary to understand how factors in these areas may influence their overall population dynamics. This thesis explored in detail the distribution ecology of migrants in the Guinea savannah, the region from where wintering migrants currently show the greatest breeding population declines. In particular, I investigated some prevailing but hitherto little tested ecological hypothesis concerning impacts of geographical, vegetation and anthropogenic characteristics on the densities and winter distribution of migrants in Africa. Migrant distribution seemed to fit a pattern where decisions leading to winter habitat choice and association were hierarchical and jointly influenced by factors extrinsic and intrinsic to the habitats at large and finer scales respectively. Migrants were distributed in reasonable densities across a wide range of habitats. There was also evidence for an independent effect of latitude on densities and distribution, even after controlling for habitat characteristics. There was no evidence of large changes in latitudinal density patterns within a given winter season and site density patterns were generally consistent over the study duration. Migrants and taxonomically-related/ecologically similar Afrotropical residents showed similarities in habitat requirements and utilization, although migrants utilized habitats over a wider latitudinal range. Some migrants tended to show correspondence in site occurrence between consecutive winters but less so within a given winter season and there was an overall low transferability of habitat models for Palearctic migrants between sites in Nigeria. Collectively, the results describe distribution mechanisms typical for ecologically flexible species that can best be described as habitat generalists. As generalists, migrants are expected to show some resilience, especially in dealing with local and small scale changes on their wintering grounds such that these are unlikely to be the primary limiting factor in their population dynamics. However, the scale of ongoing habitat change across much of Africa is perhaps contributing to overcome the resilience engendered by their generalism. Conservation efforts for these mainly generalists species may therefore aim to preserve habitat on a large scale, perhaps through the promotion of sustainable land use practices.

Two sympatric species of dolphins (Atlantic spotted dolphins, Stenella frontalis and Atlantic bottlenose dolphins, Tursiops truncatus) have been long-term residents to Little Bahama Bank. This study assessed whether there was a change in residence patterns or diurnal foraging depths of bottlenose dolphins following a large emigration event in the resident spotted dolphin community on this sandbank. Photo-identification was used to identify individual bottlenose dolphins and compare pooled years before (2010-2012) and after (2013-2015) the spotted dolphin emigration. The identified community size and overall residency of the bottlenose dolphins remained similar, although two bottlenose dolphins emigrated over deep water to the site spotted dolphins emigrated. Bottlenose dolphins diurnally fed in shallower water but remained in the same geographic foraging locations. Reasons remain unknown for this depth change, but potential changes in the productivity of primary bottlenose dolphin foraging habitats or reduction of spotted dolphins from shallower depths remain possibilities. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Thesis (MTech (Conservation and Marine Sciences))--Cape Peninsula University of Technology, 2016. / Invasive alien plant species pose a major threat to global biodiversity by displacing native vegetation and transforming habitats. In South Africa, invasive alien plants have become a major component of most habitats. River systems are particularly affected owing to their dynamic nature and to anthropogenic activities. This has resulted in fynbos riparian scrub vegetation being replaced mainly by Acacia and Eucalyptus species, with serious ecological and economic impacts. The presence of alien trees along river banks leads to a reduction in native plant species richness and their high water consumption adds on to the existing water challenges in an already dry country. However, with regards to native fauna, it largely remains unknown both at small or large spatial scale, whether alien trees provide additional habitat which increases biodiversity, or if their presence leads to a reduction of native biodiversity. Impacts on water supply have led to large-scale clearing of invasive alien trees from riparian zones by the government through the Working for Water (WfW) programme. Monitoring and evaluation studies carried out after clearing are not well-rounded and mostly focus on vegetation response to clearing. Although some of these studies have reported successful restoration through passive methods, ecosystem recovery remains partial. There is evidently a lack of information regarding the response of animal communities to invasive alien plant clearing. Therefore, the main objective of this thesis was to investigate bird assemblage response to alien tree invasion and clearing. As a study system, I used the riparian area of the Berg River within the fynbos biome of the Cape Floristic Region, South Africa. The area historically consisted of renosterveld vegetation characterised by a matrix of shrubs and a high diversity of geophytes but relatively poor avifaunal diversity. This area is heavily affected by invasive alien trees and shrubs including Eucalyptus camaldulensis. I employed bird assemblages as an indicator, and used fixed-point bird counts to compare bird species richness and bird abundance between invaded and near-pristine habitats. Invasion by E. camaldulensis significantly reduced bird species richness and abundance. In particular, nectarivores and frugivores, which play important mutualistic roles in the fynbos, were reduced and unexpectedly; there were fewer raptors in invaded areas. I proceeded to carry out a space for time substitution, comparing plant and bird assemblages in invaded sites, near-pristine sites and in sites cleared in 2005, 2007, 2008 and 2014. A general increase in bird species richness and bird abundance with time since clearing exists with bird assemblages in cleared sites being similar to those in near-pristine sites. However, bird assemblages in cleared sites have not yet fully recovered a decade after clearing and four native plant species are still absent. In the third part of my thesis I assessed the impacts of invasive alien plants on bird assemblages at a larger spatial scale. The different responses shown by bird assemblages to invasive alien plant cover depended on the intensity of invasion, spatial scale and other land uses. From a bird’s eye view, this study supports the current clearing by WfW given the significant negative effects of invasive alien plants on bird diversity both at plot and large spatial scales. However, passive restoration is unsuccessful in restoring the full complement of plants and birds, therefore, active restoration should be considered. To limit the cost, I suggest a focused restoration approach of selected keystone tree species which can assist to establish a functional native ecosystem.

Bird-vegetation associations are a base for bird conservation and management, as well as for predictions of the effects of resource management and climate change on wildlife populations. A recent shift in forest management priorities from timber production to native species' habitat conservation on federal lands has emphasized the need to understand the mechanisms underlying the effects of vegetation management on wildlife. The assumption of strong bird-vegetation relationships is rarely tested for forest birds, especially at large temporal extents, which are more likely to reveal instabilities in bird-vegetation relationships than short-term studies. This study aimed to quantify bird-vegetation relationships and investigate their strength in young thinned and unthinned Douglas-fir forest stands over ten to years post thinning. Additionally, this study investigated whether disturbance associated with forest thinning decoupled bird-vegetation relationships in the thinned and unthinned stands. I used abundance or occurrence data for eight bird species collected at 58 point count surveys, conducted during six breeding seasons over ten years following forest thinning. I obtained detailed local-scale vegetation characteristics associated with bird sampling points and modeled bird occurrence or abundance as a function of vegetation characteristics. Vegetation characteristics explaining individual species occurrence or abundance varied among species and among years for any given species. Six out of eight species showed responses to examined vegetation characteristics. For three out of six species, the effects of vegetation characteristics on bird occurrence or abundance remained consistently positive or negative over time. For the other three species the absolute effect of vegetation decreased over time to that of not statistically different from zero. The estimates of vegetation effects on bird response varied in size among years, though they were not statistically different among years. Magnitude of vegetation effect on bird occurrence or abundance did not increase with time, nor was it related to species prevalence or abundance. I found evidence of a response threshold for one species, Swainson's thrush. I suggest that changing abundance of resources, associated with thinning disturbance, demographic stochasticity associated with small population sizes, as well as large-scale demographic processes and possibly life history traits of examined species, mediate the strength of local-level bird-vegetation associations. Variability of vegetation effects on bird occurrence or abundance over time suggests a greater uncertainty of results of vegetation-related wildlife management efforts than has previously been suggested by short-term studies. Therefore, incorporation of the uncertainty of bird-vegetation relationships into predictive models and continued long-term monitoring of species response to management may be crucial for future successful and effective management decisions. / Graduation date: 2012

No description available.

L'urbanisation et la construction d'infrastructures de transports sont aujourd'hui la première cause de baisse de diversité. De par la perte d'habitat et la fragmentation du paysage qu'ils engendrent, ces ouvrages impactent les populations. Notre travail a cherché à évaluer, sur une espèce aux exigences écologiques complexes, les impacts prévisibles de la mise en place d'une Ligne à Grande Vitesse (LGV) et leurs conséquences. Nous avons étudiés la population d'Outarde canepetière Tetrax tetrax des Costières de Nîmes. A l'échelle de son aire de répartition, cette population fait figure d'exception : elle atteint localement des densités-records et développe des patterns de distributions jusqu'alors jamais rencontrés chez l'espèce. Nous avons cherché à identifier les variations locales de distribution et leur corrélation avec les paramètres d'habitat selon une grande gamme d'échelle spatiale, afin de modéliser les patterns de distribution attendus et les impacts prévisibles de la future infrastructure. / Urbanization and increasing transport infrastructure construction are known as the main cause of biodiversity loss. By habitat loss and landscape fragmentation they cause, these structures impact populations. Our work sought to assess, on a case of complex ecological requirements, foreseeable impacts of the establishment of a High Speed Line (HSL) and their consequences. We studied the population of Little Bustard Tetrax Tetrax of the Costières nîmoise area. Within its own range scale, this population is an exception: it reaches locally unusually high densities and develops distributions patterns never met previously. We sought to identify local variations in distribution and their correlation with habitat parameters in a wide range of spatial scales, to model the expected distribution patterns and expected impacts of future infrastructure.

Fish assemblages from 54 oxbow lakes in the Mississippi Alluvial Valley were sampled to identify relationships among environmental variables and fish biodiversity in floodplain lake ecosystems. Environmental variables deterministic over fish biodiversity showed a hierarchical organization and were classified as primary or secondary depending on if one variable was considered to govern another. Primary variables included depth, surface area, surrounding land use, and degree of lake-river interconnectedness. Secondary variables included suites of water quality and primary productivity variables. Maximum depth and percentage of agricultural land surrounding lakes showed strongest relationships with other ecosystem components, significantly influencing water quality, primary productivity, and fish biodiversity. I found contrasting results regarding effect of lake-river interconnectedness on fish biodiversity, but maintain that connectivity is nonetheless an important floodplain lake ecosystem component and suggest that floodplain lake management efforts focus on depth, percentage of agricultural land, and restoration of connectivity.