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Thesis (MScConsEcol (Conservation Ecology and Entomology))--University of Stellenbosch, 2009. / Habitat loss and fragmentation are two of the most pressing threats to biodiversity. Avifaunal diversity and integrity is under immense pressure from these two processes. We have made major advances in our understanding of avifaunal responses to habitat fragmentation, but mostly focus on either fragment scale and/or landscape scale influences of fragmentation on birds. A more comprehensive approach to assessing the impacts of fragmentation was used in this study. The avifaunas of two different geographical regions and bioregions were surveyed and a multiscale analysis of avifaunal responses to fragmentation was attempted. The study sites include the West Coast and East Coast Renosterveld Bioregions in the Cape Floristic Region, South Africa. Assemblage shifts, feeding guild compositional changes, species abundance variation and species persistence were examined at the three spatial scales. Time- and distance-restricted point counts were used to document birds that were directly dependent on the habitat fragments. Forty fragments were selected in each bioregion and a once-off snapshot of the avifaunal richness and diversity was obtained. Results indicate that the avifauna of the two bioregions responded differently to habitat fragmentation. In the East Coast Renosterveld Bioregion, the assemblages, guild composition and species abundances were most accurately predicted by landscape configuration. An assemblage shift occurred at 20 ha fragment area, compared to the 50 ha fragment area threshold of the West Coast Renosterveld Bioregion’s avifauna composition. In the West Coast Renosterveld Bioregion, fragment area was the better predictor of assemblage, guild composition and species abundances. However in both bioregions, the persistence of common species was equally sensitive to area and landscape scale effects.

The area of land farmed in Africa is predicted to double by the year 2050 yet very few African studies have investigated the impact of different farming intensities and regimes on bird communities. This study examined avian species richness and diversity along with the densities of some common bird species on the Jos Plateau, Nigeria, in relation to habitat features on farmland over a gradient of differing farming intensities. The study area exhibited a variety of different levels of farming which differed in the habitat available for birds. Birds normally associated with savanna woodland were more associated with less intensive farming, and open-country birds were more associated with more intensive sites, with more species of birds observed where farming was less intensive. Common species of birds using cultivated land associated with different crops, with acha and millet being the most commonly used. Tree density was the most important variable predicting avian species richness and diversity, with medium tree density predicting the highest species richness and diversity. The densities of two common farmland birds were predicted best by tree density, but varied in their responses to the habitat variables, with common bulbul, a savanna generalist, associating more with less intensive, wooded areas and red-cheeked cordon-bleu, an open savanna granivore, associating with medium intensity, more open farmland. Whinchats were common in open, intensively farmed areas with few trees and good herbaceous vegetation cover. The data presented indicates the importance of retaining natural features of savanna habitat in farmland in order to maintain high avian diversity on farmland. More detailed studies are needed in order to determine the mechanisms involved in the associations observed and collaborations between ecologists and social scientists will be necessary to develop effective policies to limit the impact of the intensification of agriculture in Africa on avian biodiversity.

The global loss of biodiversity calls for robust large-scale diversity assessment. Biological diversity is a multi-faceted concept; defined as the “variety of life”, answering questions such as “How much is there?” or more precisely “Have we succeeded in reducing the rate of its decline?” is not straightforward. While various aspects of biodiversity give rise to numerous ways of quantification, we focus on temporal (and spatial) trends and their changes in species diversity. Traditional diversity indices summarise information contained in the species abundance distribution, i.e. each species' proportional contribution to total abundance. Estimated from data, these indices can be biased if variation in detection probability is ignored. We discuss differences between diversity indices and demonstrate possible adjustments for detectability. Additionally, most indices focus on the most abundant species in ecological communities. We introduce a new set of diversity measures, based on a family of goodness-of-fit statistics. A function of a free parameter, this family allows us to vary the sensitivity of these measures to dominance and rarity of species. Their performance is studied by assessing temporal trends in diversity for five communities of British breeding birds based on 14 years of survey data, where they are applied alongside the current headline index, a geometric mean of relative abundances. Revealing the contributions of both rare and common species to biodiversity trends, these "goodness-of-fit" measures provide novel insights into how ecological communities change over time. Biodiversity is not only subject to temporal changes, but it also varies across space. We take first steps towards estimating spatial diversity trends. Finally, processes maintaining biodiversity act locally, at specific spatial scales. Contrary to abundance-based summary statistics, spatial characteristics of ecological communities may distinguish these processes. We suggest a generalisation to a spatial summary, the cross-pair overlap distribution, to render it more flexible to spatial scale.

As top-level piscivores, Bald Eagles are a compelling subject for the study of territory dynamics and are highly representative of the distinctive suite of avian species that occupy Florida Bay. Despite successful recovery of Bald Eagles (Haliaeetus leuocephalus) throughout the species range, the population breeding within Florida Bay has not mirrored this trend. Beginning in the late 1980s, Florida Bay has suffered in its capacity to support species diversity and abundance as a result of extreme changes in hydrology related to altered flows of incoming freshwater. In fact, Bald Eagle territory use in Florida Bay has declined by as much as 43% as year to year variation and sensitivity to transitions between territory states have increased. Florida Bay’s populations of other large, conspicuous fish-eating birds, including Ospreys, Great White Herons, Roseate Spoonbills, and Reddish Egrets each exhibit a similar pattern of decline. The effects of environmental degradation throughout Florida Bay are magnified at higher trophic levels. The negative trend in territory occupancy is most pronounced in southeast Florida Bay whereas effects on territory occupancy in the northwest are minimal. The presence of spatial patterns in territory occupancy, despite regionally available breeding birds, suggests that individuals are evaluating differences in habitat quality for which certain territories are no longer considered viable. Building on our current understanding of the health of this population of Bald Eagles, we have successfully implemented modeling approaches that identify key territory breeding decisions. Loss of early breeding season activity (occupied and active territories) despite maintaining high breeding success indicates that changes in territory dynamics are the result of a failure to breed and not a reproductive failure. As such, future conservation actions should promote early breeding season activity (decisions by breeding pairs to initiate nesting) in areas of Florida Bay that were historically occupied but are now abandoned. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Please read the abstract in the section 00front of this document / Thesis (DPhil (Zoology))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted

The spatial and temporal patterns in selected components of the ichthyofauna and piscivorous avifauna in the small temporarily open/closed Riet River Estuary located on the eastern seaboard of southern Africa was investigated monthly over the period August 2005 to July 2006. The ichthyofauna within the littoral zone of the estuary was sampled using a 5 m seine net (8 stations) while a 30 m seine net (4 stations) was employed to sample the fish in the channel. Bird counts were made along repeat transects along the length of the estuary. Total ichthyofaunal abundances and biomass ranged between 1.60 and 8.67 individuals m⁻² and 0.45 to 21.76 g wwt m⁻² within the littoral zone, and between 0.08 and 0.44 individuals m⁻² and 0.58 and 36.52 g wwt m⁻² in the channel of the estuary. The highest values were generally recorded during the summer months. Results of the numerical analysis indicated that the breaching events recorded over the study period did not lead to a common trend in the ichthyofaunal community. In the absence of a link to the marine environment, the ichthyofaunal community in the littoral zone was numerically dominated by the estuarine resident species, Gilchristella aestuaria and to a lesser extent by Glossogobius callidus, which collectively accounted for ca. 54% of the total ichthyofauna sampled. The establishment of a link to the marine environment coincided with increased numbers of marine breeding species including Atherina breviceps and Rhabdosargus holubi to total fish counts within the estuary. Hierarchical cluster analysis did not identify any spatial patterns in the community structure of the ichthyofauna in the littoral zone or channel zone of the estuary, which could likely be linked to the absence of any distinct horizontal patterns in salinity and temperature within the system. A total of thirteen piscivorous bird species was recorded over the study period. Of the recorded species, six species were wading piscivores, four species were aerial divers and the remaining three species were pursuit swimmers. There were no significant correlations between the estimates of the ichthyofaunal abundance and biomass and bird numbers evident during the study (P> 0.05 in both cases). The Reed Cormorant (Phalacrocorax africanus) was the dominant species throughout the study, with a mean of 8.25 (SD ± 7.90) individuals per count. Mean values of the Pied Kingfisher (Ceryle rudis) and Giant Kingfisher (Megaceryle maximus) were 3.42 (SD ± 1.20) and 1.17 (SD ± 0.60) individuals per count, respectively. The remaining species revealed mean values < 0.5 individuals per count. The highest bird numbers were recorded in winter reflecting the migration of large numbers of the Reed Cormorant into the system. Breaching events were associated with a decrease in total bird numbers, which was most likely due to loss of potential foraging habitat (littoral zone) for waders resulting from reduced water levels. Monthly food consumption by all piscivorous birds revealed large temporal variability, ranging from 26.35 to 140.58 kg per month. The observed variability could be linked to mouth phase and bird numbers.