OpenUCT :: Browsing by Author "Underhill, Les G"

Browsing by Author "Underhill, Les G"

Now showing 1 - 10 of 10

Open Access
Birds and people: studies based on citizen science and census data of Greater Gauteng, South Africa
(2018) Wala, Zingfa Jantur; Underhill, Les G
Global human population growth has been predicted to grow exponentially, to a point where it exceeds the capacity of available resources to sustain it. The consequences that such exponential increase will have on the environment has also been the focus of several research. The spatial pattern of human population has reveal uneven pattern of human population with the urban areas being subject of increased influx of human population from the rural areas in search of better economic factors. The United Nations in 2007 revealed that at least half of the world’s 6.6 billion human population was living in urban areas. This number is expected to increase to over 60% of the world's population by the end of 2050. Most of this population growth is occurring in developing countries. While the health, security and town planning amongst other consequences of this global explosion in urbanization have been well-studied and documented, the impact which urbanization is having and will have on the ecosystem and on biodiversity, especially at regional and local scales has remained an a field of knowledge that has continued to evolve especially given the variable patterns and drivers of urbanization in different regions of the world as well as the different environmental factors and biodiversity in these regions. Biodiversity monitoring has been shown to be crucial to conservation goals aimed at accessing the state and condition of biodiversity. The Second South African Bird Atlas Project (SABAP2) is a citizen science atlas project which commenced in 2007. Over a decade, SABAP2 has produced a rich source of data, capturing bird distributions in South Africa. This makes SABAP2 a powerful tool for monitoring observed changes in bird communities and by extension biodiversity through time. I examined the effect that urbanization is having on the avian biodiversity in South Africa, one of the most urbanized countries in Africa. My research was focused on the 576 pentads in the four one-degree grid cells (25S 27E, 25S 28E, 26S 27E and 26E 28E) centered on the Gauteng province, referred to as Greater Gauteng region. In addition to being very urbanized, Greater Gauteng is also the most populated area in the country, and is home to 30% of the country’s 51 million people. The region is the most atlased SABAP2 region in the country, with each pentad having a minimum of 11 full-protocol SABAP2 checklists. It thus provide opportunities for the development of tools to monitor the temporal dynamics of bird communities. The first chapter is the general introduction where I did an extensive literature review of the research subject and gave an overview of the data chapters that make up the thesis. In the second chapter, I examined spatial patterns of urbanization and avian biodiversity. I assess avian species composition in the urban and rural areas of Greater Gauteng. I categorized bird data from SABAP2 for Greater Gauteng Urban and Rural subgroups. The dataset for this chapter had 700 bird species. 644 showed no range preference for either urban or rural areas. Five species showed a preference for rural areas while 51 species showed a preference for urban areas. The higher species richness recorded in urban pentads highlights the often overlooked benefits of biodiversity conservation efforts in urban areas such as green spaces and parks, gardens and water bodies. This chapter highlights the need for conservation efforts to be targeted at birds and other biodiversity in urban spaces. It is also raises the need to further promote policies aimed at having conservation efforts incorporated into town planning. In the third and fourth chapters, I used data from SABAP2 to investigate how different protected areas such as Important Bird Areas (IBAs) are to their surrounding areas by demonstrating how different the Devon Grasslands (Chapter 3) and Suikerbosrand Nature Reserve (Chapter 4) IBAs are to their immediate surrounding areas in terms of avian species richness and assemblage. Atlas data from the pentads covering these two IBAs were compared with data from the surrounding pentads. Both IBAs stand out as having more bird species than their immediate surroundings. The simple yet effective method used in this chapters can be applied in identifying potential sites for biodiversity conservation. In the fifth chapter, using a variation of the Shannon-Weiner species diversity index which is known to reach an asymptote rapidly even while species richness keeps increasing, to investigate patterns of spatial distribution of species richness and proportional diversity in Greater Gauteng. The chapter provides insights into pentads with the richest bird communities and also provides a method which can be applied to citizen science data such as SABAP2 to discover areas where particular groups of species, such as waterbirds and threatened species, are concentrated in the region. The sixth chapter examines the relationship between reporting rates of birds and human population in Greater Gauteng. With Greater Gauteng being the most populated region in South Africa, it presented an ideal situation to investigate patterns of correlation between human population and the reporting rates of bird species in the region. Based on the results obtained, the species were grouped into 18 groups categorized by the relationship pattern revealed by species reporting rates and human population. The Seventh chapter follows a similar pattern with chapter six. However, chapter seven, examines patterns between a socio-economic index, mean income per person, and the reporting rates of birds in Greater Gauteng. The eighth chapter is the conclusion. It gives a synthesis of the thesis and presents the implications for conservation of avian biodiversity in Greater Gauteng. Overall, this thesis highlights the contribution of citizen science can make to research. It also makes for a strong case showing fundamental importance of large volumes of data such as SABAP2 data, and the useful information that can be harnessed from this data. The conservation-relevant studies in the chapters of this thesis are a result of the spatial distribution patterns of the avifauna revealed by SABAP2 data from Greater Gauteng. It showed how we can detect changes in species abundance, richness and composition in a pentad or in any area, a method we can extend further to detect when bird species are starting to decline or drop out of the species list for a pentad. The results reported in this thesis provides a rich field of study for future research, especially in the field of urban ecology.
Open Access
Drivers of bird species richness within moist high-altitude grasslands in eastern South Africa
(Public Library of Science, 2016) Maphisa, David H; Smit-Robinson, Hanneline; Underhill, Les G; Altwegg, Res
Moist high-altitude grasslands in South Africa are renowned for high avifaunal diversity and are priority areas for conservation. Conservation management of these areas conflicts with management for other uses, such as intensive livestock agriculture, which requires annual burning and leads to heavy grazing. Recently the area has become target for water storage schemes and renewable electricity energy projects. There is therefore an urgent need to investigate environmental factors and habitat factors that affect bird species richness in order to optimise management of those areas set aside for conservation. A particularly good opportunity to study these issues arose at Ingula in the eastern South African high-altitude grasslands. An area that had been subject to intense grazing was bought by the national power utility that constructed a pumped storage scheme on part of the land and set aside the rest for bird conservation. Since the new management took over in 2005 the area has been mostly annually burned with relatively little grazing. The new management seeks scientific advice on how to maintain avian species richness of the study area. We collected bird occurrence and vegetation data along random transects between 2006 and 2010 to monitor the impact of the new management, and to study the effect of the habitat changes on bird species richness. To achieve these, we convert bird transect data to presence only data to investigate how bird species richness were related to key transect vegetation attributes under this new grassland management. First we used generalised linear mixed models, to examine changes in vegetation grass height and cover and between burned and unburned habitats. Secondly, we examined how total bird species richness varied across seasons and years. And finally we investigated which habitat vegetation attributes were correlated with species richness of a group of grassland depended bird species only. Transects that were burned showed a larger decrease in vegetation cover compared to transects that were not burned. Grass height increased over time. Bird species richness was highest in summer compared to other seasons and increased over time. Overall bird species richness increased over the three summer surveys but species richness of birds that prefer heavily grazed habitat showed little change over the three years. Changes in bird species richness were best explained by the model with grass height for combined species richness of grassland depended birds but also for birds that prefer heavy grazing when treated alone. On one hand birds that prefer moderate grazing were best explained by a null model. However, overall bird species richness was better positively correlated to grass height than grass cover or dead grass. We conclude that frequent burning alone with relatively reduced grazing led to higher but less dense grass, which benefited some species and disadvantaged others. We suggest that management of this grassland use combination of fire and grazing and leave some areas unburned to accommodates birds of various habitat needs.
Open Access
Environmental influences on the abundance and sexual composition of white sharks Carcharodon carcharias in Gansbaai, South Africa
(Public Library of Science, 2013) Towner, Alison V; Underhill, Les G; Jewell, Oliver J D; Smale, Malcolm J
The seasonal occurrence of white sharks visiting Gansbaai, South Africa was investigated from 2007 to 2011 using sightings from white shark cage diving boats. Generalized linear models were used to investigate the number of great white sharks sighted per trip in relation to sex, month, sea surface temperature and Multivariate El Niño/Southern Oscillation (ENSO) Indices (MEI). Water conditions are more variable in summer than winter due to wind-driven cold water upwelling and thermocline displacement, culminating in colder water temperatures, and shark sightings of both sexes were higher during the autumn and winter months (March-August). MEI, an index to quantify the strength of Southern Oscillation, differed in its effect on the recorded numbers of male and female white sharks, with highly significant interannual trends. This data suggests that water temperature and climatic phenomena influence the abundance of white sharks at this coastal site. In this study, more females were seen in Gansbaai overall in warmer water/positive MEI years. Conversely, the opposite trend was observed for males. In cool water years (2010 to 2011) sightings of male sharks were significantly higher than in previous years. The influence of environmental factors on the physiology of sharks in terms of their size and sex is discussed. The findings of this study could contribute to bather safety programmes because the incorporation of environmental parameters into predictive models may help identify times and localities of higher risk to bathers and help mitigate human-white shark interactions.
Open Access
Hand-rearing, release and survival of african penguin chicks abandoned before independence by moulting parents
(Public Library of Science, 2014) Sherley, Richard B; Waller, Lauren J; Strauss, Venessa; Geldenhuys, Deon; Underhill, Les G; Parsons, Nola J
The African penguin Spheniscus demersus has an ‘Endangered’ conservation status and a decreasing population. Following abandonment, 841 African penguin chicks in 2006 and 481 in 2007 were admitted to SANCCOB (Southern African Foundation for the Conservation of Coastal Birds) for hand-rearing from colonies in the Western Cape, South Africa, after large numbers of breeding adults commenced moult with chicks still in the nest. Of those admitted, 91% and 73% respectively were released into the wild. There were veterinary concerns about avian malaria, airsacculitis and pneumonia, feather-loss and pododermatitis (bumblefoot). Post-release juvenile (0.32, s.e. = 0.08) and adult (0.76, s.e. = 0.10) survival rates were similar to African penguin chicks reared after oil spills and to recent survival rates recorded for naturally-reared birds. By December 2012, 12 birds had bred, six at their colony of origin, and the apparent recruitment rate was 0.11 (s.e. = 0.03). Hand-rearing of abandoned penguin chicks is recommended as a conservation tool to limit mortality and to bolster the population at specific colonies. The feasibility of conservation translocations for the creation of new colonies for this species using hand-reared chicks warrants investigation. Any such programme would be predicated on adequate disease surveillance programmes established to minimise the risk of disease introduction to wild birds.
Open Access
A Knowledge-based approach to wildlife management
(Southern African Wildlife Management Association, 2008) Paterson, Barbara; Brown, Chris J; Stuart-Hill, Greg; Winschiers, Heike; Underhill, Les G; Dunne, Tim T; Schinzel, Britta; Beytell, Ben; Demas, Fanuel; Lindeque, Pauline; Weaver, Chris
We present a method for developing a knowledge base to give wildlife managers timely access to pertinent information. This knowledge-based approach to species management in Namibia focuses on anthologies and management strategies for high-value mammal species.To manage wildlife resources sustainably access to an appropriate knowledge base is essential. The strategic species management approach promotes planning on local, national, and international levels. A hypermedia Information System for Rare Species Management (IRAS) and a decision support system (Wildlife Introduction Advisor) are described. Unlike print media, which become dated, hypermedia is easily updated. The non-sequential nature of hypermedia allows information extraction according to the readers needs. Due to this flexibility hypermedia supports adaptive management and information sharing. Usability evaluation of the IRAS system disproved our assumption that established wildlife conservation categories such as habitat, distribution, and numbers are appropriate and sufficient to structure species information. This result led to a restructuring of the information according to management objectives. Evaluation of the Wildlife Introduction Advisor indicates that the model performs reliably and is robust towards input error. Human experts seem to be susceptible to bias. The economic benefits associated with wildlife translocations demand accountability through a well-defined, transparent distribution process. In Namibia this demand is achieved through the use of a knowledge-based decision support tool.
Open Access
Overlap in utilization of juvenile Cape Horse Mackerel by Cape Fur Seals and the purse-seine fishery in Namibia
(Southern African Wildlife Management Association, 2007) Mecenero, Silvia; Underhill, Les G; Krakstad, Jens-Otto; Kirkman, Stephen P; Roux, Jean-Paul
The Cape horse mackerel Trachurus trachurus capensisis one of Namibia's most valuable fish stocks, and an important component to the diet of Cape fur seals, Arctocephalus pusillus pusillus, off northern Namibia. The level of overlap in the utilization of this resource between seals and the purse-seine fishery was investigated using two overlap indices. For high overlap measures, seals and the purse-seine fishery utilized age-2 horse mackerel. For low overlap measures, seals mainly consumed age-0 fish whereas the fishery caught age-2 fish. Both indices were adjusted by the proportion of horse mackerel in the seal diet, with the assumption that the proportion consumed by the seals reflects the abundance of horse mackerel in the coastal waters of Cape Cross, Namibia. Both unadjusted and adjusted overlap indices showed that overlap between seals and the fishery in their utilization of juvenile horse mackerel was high only at times when horse mackerel abundance was high, and low when abundance was small. Confidence intervals and significance testing were included. Overall, there was little overlap between seals and the purse-seine fishery. This study provides important information that should be taken into account in the management of the horse mackerel resource.
Open Access
Ranging Behaviour of Verreaux's Eagles during the Pre-Breeding Period Determined through the Use of High Temporal Resolution Tracking
(Public Library of Science, 2016) Murgatroyd, Megan; Underhill, Les G; Bouten, Willem; Amar, Arjun
Information on movement ecology is key in understanding the drivers and limitations of life history traits and has a potential role in indicating environmental change. Currently we have a limited understanding of the parameters of movement of territory-bound raptors, which are sensitive to environmental change. In this study we used GPS tracking technology to obtain spatially (within 3 m) and temporally ( c . 3 mins) high-resolution movement data on a small sample of Verreaux's eagle Aquila verreauxii during the pre-laying period ( n = 4) with one additional example during the chick rearing period. We present GPS-derived home range estimates for this species and we examine temporal (timing, duration, frequency and speed) and spatial (total path length and maximum distance from nest) patterns of trips away from the nest. For eagles tagged in the agriculturally developed Sandveld region ( n = 3), which is made up of a mosaic of land use types, we also undertook a habitat selection analysis. Home ranges were small and largely mutually exclusive. Trip activity was centred around midday, which is likely to be related to lift availability. Our habitat selection analysis found that eagles selected for near-natural and degraded habitat over natural or completely modified areas, suggesting that these eagles may have benefitted from some of the agricultural development in this region. Although our sample sizes are small, the resolution of our tracking data was essential in deriving this data over a relatively short time period and paves the way for future research.
Restricted
S24-1 Progress with the statistical analysis of primary molt
(Current Zoology, 2006) Underhill, Les G; Serra, Lorenzo; Brandão, Anabela
This paper considers two extensions to the statistical analysis of primary molt. The first extension relates to the development of statistical models that allow the simultaneous estimation of molt parameters for diverse groups of birds. Parameter estimation uses the method of maximum likelihood and the EM algorithm. The likelihood ratio criterion is applied in statistical hypothesis-testing for equality of sets of parameters, and the Akaike Information Criterion is used to guide model selection. This extension is illustrated using primary molt data for willow warblers (Pylloscopus trochilus) over 11 years. The second extension is the realization that important insights into the way that primary molt is incorporated into the annual cycle of birds can be obtained by investigating the parameters of molt of individual primary feathers. This extension is illustrated using six data sets from four species of waders, Charadriiformes.
Open Access
The efficacy of culling seals seen preying on seabirds as a means of reducing seabird mortality
(2009) Makhado, Azwianewi B; Meÿer, Mike A; Crawford, Robert J M; Underhill, Les G; Wilke, Chris
In the 2006/2007 breeding season of Cape gannets Morus capensis at Malgas Island, the removal of 61 Cape fur seals Arctocephalus pusillus pusillus that preyed on gannet fledglings when they left to sea significantly reduced the mortality rate of these fledglings. However, because seals learned to avoid the boat used for their removal, it was not possible to remove all the seals that killed gannet fledglings and some mortality continued. The seals inflicting the mortality were all sub-adult males, with an average age of <5 years. Sustained removal of these animals may reduce this feeding behaviour, which is at present having an adverse impact on several threatened seabirds in the Benguela ecosystem.
Open Access
Woody cover and birds
(2018) Loftie-Eaton, Megan; Underhill, Les G
Major influences on biodiversity in general and on species distributions in particular have occurred on South African landscapes over time as a result of human activities and climate change. Landscapes in southern Africa are not only a product of changes in climate, but they are also a product of the changes brought about by people and their land management practices. In recent decades, bush encroachment has increased dramatically throughout the Savanna Biome of South Africa. Bush encroachment is a vegetation dynamic of global interest. It refers to the thickening or increase of woody vegetation (trees and shrubs) at the expense of grasses and/or herbaceous vegetation. In many areas across South Africa, systems that were once open grassland have become dense thickets dominated by trees and shrubs. Bush encroachment is driven by global factors like increasing carbon dioxide (CO2) levels in the atmosphere as well as local factors like grazing pressures and fire management practices. In Africa, it has long been recognized that there is an influence of vegetation patterns and structure on the distribution and abundance of birds. Changes in habitats due to an increase or decrease in woody cover has been linked to changes in bird diversity and community structure. This thesis looks at what impacts bush encroachment has had on bird distributions in eastern South Africa, with a special focus on the Kruger National Park as well as Palearctic migrants. Chapter 2 of the thesis develops a new quantitative method to relate bird distributions to woody cover. The algorithm is experimental, and an important aspect of the chapter is to investigate whether the results obtained coincide with expectations. The approach first estimates the proportion of the bird species in an area which occur in each woody cover category in a region. It also calculates the proportion of the area of the region which is in each woody cover category. It then uses Jacobs Index to provide an estimate of the extent of preference/avoidance of each species for each woody cover category, on a scale that runs from +1 (the entire population of the species is in that woody cover category) to –1 (none of the population of the species is in that woody cover category). The method is tested on a region consisting of three one-degree grid cells spanning Mpumalanga, Limpopo and Gauteng which include a diversity of woody cover categories, from grassland (no woody cover) to savanna to dense woodland. Chapter 3 applies this approach to the birds of the Kruger National Park, examining which species have distributions which can, and which cannot, be explained to a greater or lesser extent by a preference for a particular range of woody covers. Bird species are selected for close monitoring for ecological management purposes of the Kruger National Park. Chapter 4 considers a set of 10 bird species, all of which are migrants to South Africa from Eurasia, and occur to a large extent during their non-breeding period within the savanna biome of South Africa. For each species, the extent of increase in relative abundance between the first and second bird atlas projects in the region (SABAP1 and SABAP2) is estimated. In most cases, the change of relative abundance can be explained in terms of bush encroachment. The likely provenance of these species in Eurasia is considered; for most species, this area lies in southwestern Asia, i.e. the Ukraine and adjacent Russia. Changes in habitat in this region are also considered and help to improve the understanding of how the populations in South Africa have changed.

Browsing by Author "Underhill, Les G"

Results Per Page

Sort Options