A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science October 2012 Johannesburg, South Africa / Food is not always readily available and therefore an important limiting resource to birds. South African forests have a similar fruiting and flowering phenology to tropical forests in that food availability fluctuates over space and time. South African indigenous forest is naturally fragmented in a non-forest matrix and therefore differs from tropical forests. Anthropogenic landuse change has contributed to the increased fragmentation of indigenous forest. The isolated nature of patches provides a suitable platform from which to assess changes in a forest bird community between seasons because they are structurally and functionally distinct from the surrounding vegetation. Therefore, the aim of the study was to assess food as a driver of community dynamics and dietary patterns of birds in a Mist Belt Mixed Podocarpus forest patch between two distinct seasons, winter and summer. This was assessed through a combination of field techniques and stable isotope analysis of carbon and nitrogen. Further, birds were categorised as forest specialists, forest generalists, and forest visitors based on published information to provide extra insight into community changes. Species richness and abundance differed between seasons due to the local movements and turnover of birds and due to the influx of migrants into the forest. In addition, nectarivores and frugivores increased in abundance and biomass in the forest in winter when flowers and fruit were readily available from canopy trees, such as Halleria lucida and Podocarpus latifolius. However, insect-eating guilds increased in summer when there was a greater diversity of invertebrates. Nectarivores, granivores, and omnivores vertically tracked food within forest height strat to where it was most abundant, demonstrating a close association with the location of their food resources. Further, the niche of several species, particularly insectivores and nectarivores, broadened in winter when food resources were limited. However, there was niche contraction in several bird species in summer when resources were more readily available. Overall, the forest acted as a refuge for guilds, particularly frugivores and nectarivores, in winter. Furthermore, this study suggested that food limitation is species-specific and does not apply to all species. Understanding the drivers of community change has important implications for forest management and conservation of forest flora and fauna.

I studied foraging ecology of black oystercatchers (Haematopus bachmani) in the rocky intertidal. The aims of this study were: 1) to analyze prey choice and patch choice by adult black oystercatchers and evaluate how well their foraging performance was predicted by foraging theory; 2) to study development of foraging in young oystercatchers; 3) to indirectly examine the relationship between parental foraging performance and fitness by measuring chick growth and chick production. The following conclusions were reached: 1) Prey selection by oystercatchers was generally as predicted by theory, but birds showed partial preferences for prey. Patch choice followed general theoretical predictions, but profitabilities achieved within particular patch types were highly variable. Reasons for this are discussed. 2) Growth and physical maturation are important components in development of foraging. During the period of this study, chicks were heavily dependent on parental feeding, and the ability of chicks to forage independently developed after chicks left their natal area at about 50 days of age. 3) Chick growth varied between one-chick and two-chick broods, and this may be related to parental foraging performance. However, during this study chick production was constrained by weather and predation, and no relationship between parental foraging performance and fitness could be defined. / Science, Faculty of / Zoology, Department of / Graduate

The use of precision automated electronic balances has allowed remote quantification of instantaneous and long term body mass changes in breeding swallows, Hirundo rustica. By means of observation, experiment and optimality modelling, the extent of mass changes during incubation and nestling rearing are described, and the fitness consequences of mass changes discussed. An understanding of the causes and consequences of mass changes in swallows is developed from laboratory investigations of short term mass changes in canaries Serinus canarius, and from carcass analysis of breeding sand martins R. riparia, and swallows. Parent: offspring resource allocation was investigated during incubation in swallows. A model is developed which assumes that fitness is maximised in individuals which spend most time on the nest as a result of maximising the difference between net gain while foraging and clutch reheating costs, measured in units of energy. The model is tested, and the most frequently observed inattentive period proves, to be similar to that predicted to be the most energetically profitable. The early decline in swallow body mass during nestling rearing is likely to represent a 'programmed' anorexia in females during the brooding phase, whereby mass loss is beneficial in reducing flight costs and releasing energy available for work. After termination of brooding, however, mass losses were associated with rapid feeding rates to the brood for both sexes, and were judged to be potentially costly in terms of adult survival. (ii) By concurrent monitoring of resources for parents and offspring, investment in self-maintenance relative to investment in offspring is calculated, and the results interpreted in the wider context of lifehistory tactics and parental investment theories. Both sexes of swallow invested more in 'self' relative to 'offspring' when food was scarce or when feeding broods of small metabolic mass. Females appeared to risk their body mass falling to lower levels than that of their mates when feeding conditions were poor. overall, the study showed that the costs and benefits of mass changes in swallows differed according to the stage of the breeding cycle, and that detailed knowledge of the causes of mass changes allows insight into the evolution of reproductive strategies of birds of both sexes in relation to individual quality and resource availability.

Thesis (PhD)--University of Stellenbosch, 2010. / The aim of the study was to assess the importance of spatial and temporal variation in diet quality and abundance for determining sustainable stocking rates on commercial, communal and game ranches in a semi-arid savanna, with the ultimate goal of avoiding land degradation in the long term, to provide sustainable livelihoods in rangelands and to make policy that will help in managing the available natural resources in the rangelands. Thus, firstly the effects of grazing, fire, nitrogen and water availability on nutritional quality of grass in semi-arid savanna was assessed. Secondly, spatial and temporal variation in plant quantity and quality among management (commercial, communal and game) types and habitat types (open savanna, rocky, shrubby and pans) and stocking rates in different management types were determined. Thirdly, the quality and quantity of variation inside and outside herbivore exclosures among commercial, communal and game management and habitat types in the semi arid savanna were estimated. Fourthly, faecal profiling was used to assess the effects of different management types on diet quality in semi-arid savanna. Lastly, policy based on the results of the present study was formulated.