A contribution to the biology of the sociable weaver Philetairus socius (Latham)
- Authors: Maclean, Gordon L
- Date: 1967
- Subjects: Weaverbirds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5863 , http://hdl.handle.net/10962/d1012791
- Description: Anyone who has travelled the dusty road in the bed of the Kuruman River from Kuruman in the Northern Cape to the South West African border at Rietfontein cannot fail to have been impressed by the large communal nests of the sociable weaver Philetairus socius which adorn many of the camelthorn trees along the way. One of the earliest reports of the bird and its nest is that of Sir Andrew Smith (1849) who passed that way through what was then Latakoo (the present day Kuruman), collecting birds which he described for the first time. To him we are indebted for the first published illustrations of the sociable weaver, its nest and egg, and a brief account, not entirely accurate to be sure, of the building and occupation of the nest. This account has since been quoted at length by Shelley (1905) and by Friedmann (1930a) who accepted Smith's statements as they stood. Some years after Smith's travels, Anderson wrote (1872) that the flocks of sociable weavers " ... incubate their eggs under the same roof, which is composed by these birds of whole cartloads of grass piled on a branch of some kamel-thorn tree in one enormous mass of an irregular umbrella-shape, looking like a miniature haystack, and almost solid, but with the under surface, which is nearly flat, honeycombed all over with little cavities, which serve not only as places for incubation but also as a refuge against rain and wind". This account gives some idea of the spectacular nests built by these birds which are hardly larger than a sparrow. But, living in the dry and thinly-populated western regions of southern Africa, the sociable weaver remained a remote curiosity, the subject of casual reports and some strange ideas. Since Friedmann (1930a) studied the sociable weaver briefly in the western Transvaal, the only thorough field observations (mainly on nests and nest sites) up to the present have been those of Rudebeck (1953, 1956). Collias & Collias (1964) returned to the western Transvaal some 20 years after Friedmann's visit, but unfortunately had time for only a cursory study; their main interest was once again in the nest and its architecture. Thus, in 1964 when I joined Dr. T.J. Cade, then of Syracuse University and now of Cornell University, on his desert biology programme, he suggested that the sociable weaver be the subject of special study in the Kalahari. Here was a bird, resident in a harsh environment, living throughout the year in an extraordinary nest, and almost completely unknown biologically. Among the questions to be answered were: How is the nest started and how is it constructed? Which birds build, and how is the labour organized? What is the purpose of the elaborate nest: does it provide a micro-climate which enables the birds to survive better under arid conditions? How could such a communal nest have evolved? What is the social organization of the colony in and out of the breeding season? When do the birds breed and what factors induce breeding? What happens to the young birds after they become independent of their parents? Naturally many other questions arose as the work proceeded, but these were the main ones on which the project was initiated.
- Full Text:
- Date Issued: 1967
- Authors: Maclean, Gordon L
- Date: 1967
- Subjects: Weaverbirds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5863 , http://hdl.handle.net/10962/d1012791
- Description: Anyone who has travelled the dusty road in the bed of the Kuruman River from Kuruman in the Northern Cape to the South West African border at Rietfontein cannot fail to have been impressed by the large communal nests of the sociable weaver Philetairus socius which adorn many of the camelthorn trees along the way. One of the earliest reports of the bird and its nest is that of Sir Andrew Smith (1849) who passed that way through what was then Latakoo (the present day Kuruman), collecting birds which he described for the first time. To him we are indebted for the first published illustrations of the sociable weaver, its nest and egg, and a brief account, not entirely accurate to be sure, of the building and occupation of the nest. This account has since been quoted at length by Shelley (1905) and by Friedmann (1930a) who accepted Smith's statements as they stood. Some years after Smith's travels, Anderson wrote (1872) that the flocks of sociable weavers " ... incubate their eggs under the same roof, which is composed by these birds of whole cartloads of grass piled on a branch of some kamel-thorn tree in one enormous mass of an irregular umbrella-shape, looking like a miniature haystack, and almost solid, but with the under surface, which is nearly flat, honeycombed all over with little cavities, which serve not only as places for incubation but also as a refuge against rain and wind". This account gives some idea of the spectacular nests built by these birds which are hardly larger than a sparrow. But, living in the dry and thinly-populated western regions of southern Africa, the sociable weaver remained a remote curiosity, the subject of casual reports and some strange ideas. Since Friedmann (1930a) studied the sociable weaver briefly in the western Transvaal, the only thorough field observations (mainly on nests and nest sites) up to the present have been those of Rudebeck (1953, 1956). Collias & Collias (1964) returned to the western Transvaal some 20 years after Friedmann's visit, but unfortunately had time for only a cursory study; their main interest was once again in the nest and its architecture. Thus, in 1964 when I joined Dr. T.J. Cade, then of Syracuse University and now of Cornell University, on his desert biology programme, he suggested that the sociable weaver be the subject of special study in the Kalahari. Here was a bird, resident in a harsh environment, living throughout the year in an extraordinary nest, and almost completely unknown biologically. Among the questions to be answered were: How is the nest started and how is it constructed? Which birds build, and how is the labour organized? What is the purpose of the elaborate nest: does it provide a micro-climate which enables the birds to survive better under arid conditions? How could such a communal nest have evolved? What is the social organization of the colony in and out of the breeding season? When do the birds breed and what factors induce breeding? What happens to the young birds after they become independent of their parents? Naturally many other questions arose as the work proceeded, but these were the main ones on which the project was initiated.
- Full Text:
- Date Issued: 1967
The biology of the South African cliff swallow hirundo spilodera
- Authors: Earlé, Roy Anthony
- Date: 1986
- Subjects: Hirundo pyrrhonota Birds -- Breeding -- South Africa Birds -- Behavior -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5631 , http://hdl.handle.net/10962/d1004927
- Description: The general biology of the South African Cliff Swallow Hirundo spilodera was studied over a two year period in the central Orange Free State. This species is highly colonial, nesting mostly on man-made structures such as concrete road bridges. Adult birds were usually faithful to their breeding colony and very few individuals changed colonies. The Cliff Swallow had a surprisingly large vocal repertoire for a swallow and contact calls of the young were individually recognizable. Three species-specific ectoparasites parasitized the Cliff Swallow but none seemed to have a noticeable negative effect on the swallows. Breeding started earlier in larger colonies than in smaller ones and conspecific brood parasitism was a common feature in some colonies. Individual pairs made up to four breeding attempts per season. The findings of this study are compared with the available information on other members of the Hirundinidae and the advantages and costs of Cliff Swallow coloniality are discussed.
- Full Text:
- Date Issued: 1986
- Authors: Earlé, Roy Anthony
- Date: 1986
- Subjects: Hirundo pyrrhonota Birds -- Breeding -- South Africa Birds -- Behavior -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5631 , http://hdl.handle.net/10962/d1004927
- Description: The general biology of the South African Cliff Swallow Hirundo spilodera was studied over a two year period in the central Orange Free State. This species is highly colonial, nesting mostly on man-made structures such as concrete road bridges. Adult birds were usually faithful to their breeding colony and very few individuals changed colonies. The Cliff Swallow had a surprisingly large vocal repertoire for a swallow and contact calls of the young were individually recognizable. Three species-specific ectoparasites parasitized the Cliff Swallow but none seemed to have a noticeable negative effect on the swallows. Breeding started earlier in larger colonies than in smaller ones and conspecific brood parasitism was a common feature in some colonies. Individual pairs made up to four breeding attempts per season. The findings of this study are compared with the available information on other members of the Hirundinidae and the advantages and costs of Cliff Swallow coloniality are discussed.
- Full Text:
- Date Issued: 1986
A comparison of nesting behaviour and prey selection in some Southern African species of Ammophila (Hymenoptera : Sphecidae)
- Authors: Weaving, Alan James Shelley
- Date: 1987
- Subjects: Hymenoptera
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5600 , http://hdl.handle.net/10962/d1002050
- Description: Nesting behaviour and prey selection was compared in eight species of Ammophila. The frequent sympatry of these species was a central point of interest in the study. Nest siting differed markedly in several species. A. ferrugineipes, A. dolichodera, A. dolichocephala and, probably, A. conifera nested mostly in open habitats, this being regarded as the most common situation for the majority of Ammophila. A. beniniensis was unusual in nesting in well vegetated habitats, A. vulcania doing so amongst small clumps of vegetation in otherwise open habitats. A. insignis nested in vertical banks or old animal burrows and A. braunsi utilised abandoned burrows of other wasps situated in non-friable clay soils. This is the first time such nest siting has been reported for Ammophila and each of these two species is consequently unique. Many aspects of nest construction behaviour, in particular methods of soil waste disposal, sealing of nests and their final coverage, differed interspecifically, in some cases intraspecifically, but often apparently in response to the habitat. With regard to nest provisioning strategies, all species hunted after digging their nests, except A. dolichodera which is the first Afrotropical Ammophila reported to hunt before excavating its nest. This brings the total number of the world's species of Ammophila showing this behaviour to three. This species, A. beniniensis, A. braunsi and A. vulcania provided one caterpillar per nest; the others supplied several, A. insignis being the only mass provisioner. A. ferrugineipes showed a form of progressive provisioning and maintained several nests at a time; it is the only Afrotropical species known so far to do so. Only two extra-limital species have been reported showing similar behaviour. The observed variations in provisioning strategies can most easily be explained in relation to the habitat. Investigation of prey selection showed that there was very little interspecific overlap in the species of caterpillars used for provisioning nests. This was shown to be due mainly to differing hunting habitat preferences. The various overall patterns of nesting behaviour, and variations in the different components within these patterns, were considered most likely to have resulted from allopatric speciation in different types of vegetation, the more advanced patterns arising in open habitats. The frequent occurrence of sympatry appears to be a reflection of a shifting distribution of mosaic patterns of vegetation types and the post-speciation spread of species. This influence of habitat on behaviour and prey selection has emphasised the need for caution in drawing phylogenetic conclusions from ethology. Further, these considerations provide an alternative to competition in attempting to explain the observed behaviour patterns and distribution of these wasps.
- Full Text:
- Date Issued: 1987
- Authors: Weaving, Alan James Shelley
- Date: 1987
- Subjects: Hymenoptera
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5600 , http://hdl.handle.net/10962/d1002050
- Description: Nesting behaviour and prey selection was compared in eight species of Ammophila. The frequent sympatry of these species was a central point of interest in the study. Nest siting differed markedly in several species. A. ferrugineipes, A. dolichodera, A. dolichocephala and, probably, A. conifera nested mostly in open habitats, this being regarded as the most common situation for the majority of Ammophila. A. beniniensis was unusual in nesting in well vegetated habitats, A. vulcania doing so amongst small clumps of vegetation in otherwise open habitats. A. insignis nested in vertical banks or old animal burrows and A. braunsi utilised abandoned burrows of other wasps situated in non-friable clay soils. This is the first time such nest siting has been reported for Ammophila and each of these two species is consequently unique. Many aspects of nest construction behaviour, in particular methods of soil waste disposal, sealing of nests and their final coverage, differed interspecifically, in some cases intraspecifically, but often apparently in response to the habitat. With regard to nest provisioning strategies, all species hunted after digging their nests, except A. dolichodera which is the first Afrotropical Ammophila reported to hunt before excavating its nest. This brings the total number of the world's species of Ammophila showing this behaviour to three. This species, A. beniniensis, A. braunsi and A. vulcania provided one caterpillar per nest; the others supplied several, A. insignis being the only mass provisioner. A. ferrugineipes showed a form of progressive provisioning and maintained several nests at a time; it is the only Afrotropical species known so far to do so. Only two extra-limital species have been reported showing similar behaviour. The observed variations in provisioning strategies can most easily be explained in relation to the habitat. Investigation of prey selection showed that there was very little interspecific overlap in the species of caterpillars used for provisioning nests. This was shown to be due mainly to differing hunting habitat preferences. The various overall patterns of nesting behaviour, and variations in the different components within these patterns, were considered most likely to have resulted from allopatric speciation in different types of vegetation, the more advanced patterns arising in open habitats. The frequent occurrence of sympatry appears to be a reflection of a shifting distribution of mosaic patterns of vegetation types and the post-speciation spread of species. This influence of habitat on behaviour and prey selection has emphasised the need for caution in drawing phylogenetic conclusions from ethology. Further, these considerations provide an alternative to competition in attempting to explain the observed behaviour patterns and distribution of these wasps.
- Full Text:
- Date Issued: 1987
Ecology and breeding biology of Lanner Falcons in the Eastern Cape Province, South Africa
- Authors: Stephenson, Alan
- Date: 2001
- Subjects: Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5667 , http://hdl.handle.net/10962/d1005352 , Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Description: Lanner Falcons Falco biarmicus are the commonest large falcons in Africa and this study in the coastal area of the Eastern Cape Province, South Africa investigated their ecology from 1984 to 2000. Lanners have recently been categorised as near-threatened and this study was initiated to ascertain if the population was stable. Breeding success of a small population, in different habitat types, was monitored intensively from 1997 to 2000, and the factors that inhibited breeding were investigated. The earliest onset of incubation was 17 July and the latest 16 August, with 2.2 young fledged per breeding pair over the four-year period. Incubation lasted 32 days and young fledged after 42-45 days. All nest sites were on cliffs with a mean height of 114 m, a mean vertical face of 53 m; 45% of the nests were in ravens’ nests. The aspect of cliff sites also influenced breeding success. Radio tracking was used to determine home range, habitat use and hunting methods, with prey species identified. Home ranges were between 66 km² and 249 km². Preferred prey was domestic chickens, pigeons and small birds during the breeding season. Foraging ranges were smaller in intensively cultivated areas with seed crops. Data obtained from ringing returns showed that no long distance movements occurred in this region, but two juveniles dispersed 152 km and 127 km. Conservation aspects with possible threats to Lanner Falcons such as poisons, electrocutions and direct persecution are discussed with some recommendations made for future research. Evidence from this study indicates that Lanner breeding success is not limited by nest site availability, but by rainfall timing and prey availability. Lanners foraged more in open areas than areas with tall vegetation, and benefited from intensive agriculture. This population appeared to be healthy and in no danger of declining in the near future.
- Full Text:
- Date Issued: 2001
- Authors: Stephenson, Alan
- Date: 2001
- Subjects: Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5667 , http://hdl.handle.net/10962/d1005352 , Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Description: Lanner Falcons Falco biarmicus are the commonest large falcons in Africa and this study in the coastal area of the Eastern Cape Province, South Africa investigated their ecology from 1984 to 2000. Lanners have recently been categorised as near-threatened and this study was initiated to ascertain if the population was stable. Breeding success of a small population, in different habitat types, was monitored intensively from 1997 to 2000, and the factors that inhibited breeding were investigated. The earliest onset of incubation was 17 July and the latest 16 August, with 2.2 young fledged per breeding pair over the four-year period. Incubation lasted 32 days and young fledged after 42-45 days. All nest sites were on cliffs with a mean height of 114 m, a mean vertical face of 53 m; 45% of the nests were in ravens’ nests. The aspect of cliff sites also influenced breeding success. Radio tracking was used to determine home range, habitat use and hunting methods, with prey species identified. Home ranges were between 66 km² and 249 km². Preferred prey was domestic chickens, pigeons and small birds during the breeding season. Foraging ranges were smaller in intensively cultivated areas with seed crops. Data obtained from ringing returns showed that no long distance movements occurred in this region, but two juveniles dispersed 152 km and 127 km. Conservation aspects with possible threats to Lanner Falcons such as poisons, electrocutions and direct persecution are discussed with some recommendations made for future research. Evidence from this study indicates that Lanner breeding success is not limited by nest site availability, but by rainfall timing and prey availability. Lanners foraged more in open areas than areas with tall vegetation, and benefited from intensive agriculture. This population appeared to be healthy and in no danger of declining in the near future.
- Full Text:
- Date Issued: 2001
Behavioural flexibility in an endangered seabird during current changes
- Authors: Traisnel, Gwendoline
- Date: 2019
- Subjects: Penguins -- South Africa , Penguins -- Behavior Sea birds -- Behavior Sea birds -- Ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43800 , vital:37048
- Description: Penguins spend a large part of their life cycle at sea and are amongst the most threatened seabirds as they suffer high mortality and have low reproductive success. Across the world, many populations are currently declining despite the constant development of conservation actions. The lack of information at the individual level reduces the understanding of individual variability and its potential role in the population dynamics of these vulnerable species. For example, long-lived species are characterised by substantial individual heterogeneity in their contribution to the overall population dynamic that should be understood when considering the implemention of conservation policies. This thesis explored some of the primary mechanisms behind inter-individual differences in behaviour and breeding success in the endangered African penguin Spheniscus demersus. On Bird island (Algoa Bay), nest defence behaviours were investigated on adults brooding chicks 1-3 weeks-old and chicks were measured at regular intervals (every 5 days) to assess their growth rate, a proxy for breeding success in this species. All adults were sexed and implanted with a passive integrated transponder which was used for individual identification. In this species, males are usually larger than females and have a higher survival rates both as juveniles and as adults. A subsample of them was equipped with tracking devices (GPSs and Time Depth Recorders), sometimes over consecutive foraging trips and across years. Finally, mate and nest fidelity were investigated to understand the drivers and consequences of this trait in that population. Breeding success was linked to nest defence behaviours, with bolder birds generally showing lower breeding success. This relation could not, however, be explained by differences in foraging strategies. Males were generally bolder than females when defending the nests, but their foraging behaviour did not vary with their personality. They generally had lower foraging effort than females. By contrast, bolder females performed more sinuous path, more wiggles and travelled larger vertical distances than shyer ones. Overall, females were more flexible than males over consecutive trips, suggesting that they probably adjust their behaviours to the offspring needs in this species. However, no sex difference in behavioural flexibility between sexes was visible across years, indicating that environmental variability may equally impact females and males’ behaviour over such time-scale. Generally, consistency was time-scale dependent as penguins increased their foraging flexibility across years, potentially adjusting to the variability of the environment. Interestingly, foraging consistency over consecutive trips increased during years of poor environmental conditions, and individuals with consistent foraging strategies were more successful than more flexible individuals when resources were extremely scarce. Finally, while nest and mate fidelity were high in this species, individuals that changed nest/partners, improved their breeding outcome. Particularly, after low breeding success females were more likely to change nest site and thereby partner to possibly improve their fitness. The potential biased adult sex ratio towards males in this population may facilitate changes in females which may have more partners available to re-mate than males. The present thesis reveals the existence of individual differences in behaviour and breeding success which relate to personality in penguins. These findings highlight the importance to integrate individual variability to predict future population dynamics in the context of global changes to understand the resilience and vulnerability of the species.
- Full Text:
- Date Issued: 2019
- Authors: Traisnel, Gwendoline
- Date: 2019
- Subjects: Penguins -- South Africa , Penguins -- Behavior Sea birds -- Behavior Sea birds -- Ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43800 , vital:37048
- Description: Penguins spend a large part of their life cycle at sea and are amongst the most threatened seabirds as they suffer high mortality and have low reproductive success. Across the world, many populations are currently declining despite the constant development of conservation actions. The lack of information at the individual level reduces the understanding of individual variability and its potential role in the population dynamics of these vulnerable species. For example, long-lived species are characterised by substantial individual heterogeneity in their contribution to the overall population dynamic that should be understood when considering the implemention of conservation policies. This thesis explored some of the primary mechanisms behind inter-individual differences in behaviour and breeding success in the endangered African penguin Spheniscus demersus. On Bird island (Algoa Bay), nest defence behaviours were investigated on adults brooding chicks 1-3 weeks-old and chicks were measured at regular intervals (every 5 days) to assess their growth rate, a proxy for breeding success in this species. All adults were sexed and implanted with a passive integrated transponder which was used for individual identification. In this species, males are usually larger than females and have a higher survival rates both as juveniles and as adults. A subsample of them was equipped with tracking devices (GPSs and Time Depth Recorders), sometimes over consecutive foraging trips and across years. Finally, mate and nest fidelity were investigated to understand the drivers and consequences of this trait in that population. Breeding success was linked to nest defence behaviours, with bolder birds generally showing lower breeding success. This relation could not, however, be explained by differences in foraging strategies. Males were generally bolder than females when defending the nests, but their foraging behaviour did not vary with their personality. They generally had lower foraging effort than females. By contrast, bolder females performed more sinuous path, more wiggles and travelled larger vertical distances than shyer ones. Overall, females were more flexible than males over consecutive trips, suggesting that they probably adjust their behaviours to the offspring needs in this species. However, no sex difference in behavioural flexibility between sexes was visible across years, indicating that environmental variability may equally impact females and males’ behaviour over such time-scale. Generally, consistency was time-scale dependent as penguins increased their foraging flexibility across years, potentially adjusting to the variability of the environment. Interestingly, foraging consistency over consecutive trips increased during years of poor environmental conditions, and individuals with consistent foraging strategies were more successful than more flexible individuals when resources were extremely scarce. Finally, while nest and mate fidelity were high in this species, individuals that changed nest/partners, improved their breeding outcome. Particularly, after low breeding success females were more likely to change nest site and thereby partner to possibly improve their fitness. The potential biased adult sex ratio towards males in this population may facilitate changes in females which may have more partners available to re-mate than males. The present thesis reveals the existence of individual differences in behaviour and breeding success which relate to personality in penguins. These findings highlight the importance to integrate individual variability to predict future population dynamics in the context of global changes to understand the resilience and vulnerability of the species.
- Full Text:
- Date Issued: 2019
Some aspects of an ethological study of the aculeate wasps and the bees of a karroid area in the vicinity of Grahamstown, South Africa
- Authors: Gess, Friedrich Wolfgang
- Date: 1980
- Subjects: Wasps -- South Africa Bees -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5834 , http://hdl.handle.net/10962/d1009445
- Description: From introduction: The present study is the first attempt in southern Africa to consider an entire community of aculeate wasps and bees and their interactions with their environment as manifested by their ethology. As far as the author has been able to ascertain it is in fact the most comprehensive of its kind to have been undertaken anywhere, the only similar but more restricted account of this nature being that of Evans (1970) which is mainly concerned with fossorial species and their associates.
- Full Text:
- Date Issued: 1980
- Authors: Gess, Friedrich Wolfgang
- Date: 1980
- Subjects: Wasps -- South Africa Bees -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5834 , http://hdl.handle.net/10962/d1009445
- Description: From introduction: The present study is the first attempt in southern Africa to consider an entire community of aculeate wasps and bees and their interactions with their environment as manifested by their ethology. As far as the author has been able to ascertain it is in fact the most comprehensive of its kind to have been undertaken anywhere, the only similar but more restricted account of this nature being that of Evans (1970) which is mainly concerned with fossorial species and their associates.
- Full Text:
- Date Issued: 1980
A study of the ecology, behaviour and systematics of Tockus Hornbills
- Authors: Kemp, Alan Charles
- Date: 1973
- Subjects: Birds -- South Africa -- Kruger National Park -- Identification Birds -- South Africa -- Kruger National Park -- Ecology Birds -- South Africa -- Kruger National Park -- Breeding Birds -- Birds -- South Africa -- Kruger National Park -- Nutrition Birds -- South Africa -- Kruger National Park -- Physiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5861 , http://hdl.handle.net/10962/d1012634
- Description: During the last decades ecology and behaviour have become of major importance in African ornithology. Not only have more individual species been studied in detail, but behaviour and ecology have been used in a more general sense in regional works (Benson et al 1971} and in zoogeographical treatises (Moreau 1966, Hall and Moreau 1970). As part of a world- wide trend, behaviour and ecology have also become important in systematics and taxonomy eg. Hall's 1963 study of francolin, and Benson et al's 1971 erection of the bush shrike family Malaconotidae. This dissertation fits into this trend, beginning with a detailed study of the ecology and behaviour of three species of hornbill of the genus Tockus, and extending the observations in less detail to five other members of the genus. Combined with the literature, these observations allow an analysis of the systematics and evolution of the genus Tokus to be undertaken, as well as supplying descriptive information on Tokus biology. Intro. p. 1.
- Full Text:
- Date Issued: 1973
- Authors: Kemp, Alan Charles
- Date: 1973
- Subjects: Birds -- South Africa -- Kruger National Park -- Identification Birds -- South Africa -- Kruger National Park -- Ecology Birds -- South Africa -- Kruger National Park -- Breeding Birds -- Birds -- South Africa -- Kruger National Park -- Nutrition Birds -- South Africa -- Kruger National Park -- Physiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5861 , http://hdl.handle.net/10962/d1012634
- Description: During the last decades ecology and behaviour have become of major importance in African ornithology. Not only have more individual species been studied in detail, but behaviour and ecology have been used in a more general sense in regional works (Benson et al 1971} and in zoogeographical treatises (Moreau 1966, Hall and Moreau 1970). As part of a world- wide trend, behaviour and ecology have also become important in systematics and taxonomy eg. Hall's 1963 study of francolin, and Benson et al's 1971 erection of the bush shrike family Malaconotidae. This dissertation fits into this trend, beginning with a detailed study of the ecology and behaviour of three species of hornbill of the genus Tockus, and extending the observations in less detail to five other members of the genus. Combined with the literature, these observations allow an analysis of the systematics and evolution of the genus Tokus to be undertaken, as well as supplying descriptive information on Tokus biology. Intro. p. 1.
- Full Text:
- Date Issued: 1973
A Bayesian approach to tilted-ring modelling of galaxies
- Authors: Maina, Eric Kamau
- Date: 2020
- Subjects: Bayesian statistical decision theory , Galaxies , Radio astronomy , TiRiFiC (Tilted Ring Fitting Code) , Neutral hydrogen , Spectroscopic data cubes , Galaxy parametrisation
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145783 , vital:38466
- Description: The orbits of neutral hydrogen (H I) gas found in most disk galaxies are circular and also exhibit long-lived warps at large radii where the restoring gravitational forces of the inner disk become weak (Spekkens and Giovanelli 2006). These warps make the tilted-ring model an ideal choice for galaxy parametrisation. Analysis software utilizing the tilted-ring-model can be grouped into two and three-dimensional based software. Józsa et al. (2007b) demonstrated that three dimensional based software is better suited for galaxy parametrisation because it is affected by the effect of beam smearing only by increasing the uncertainty of parameters but not with the notorious systematic effects observed for two-dimensional fitting techniques. TiRiFiC, The Tilted Ring Fitting Code (Józsa et al. 2007b), is a software to construct parameterised models of high-resolution data cubes of rotating galaxies. It uses the tilted-ring model, and with that, a combination of some parameters such as surface brightness, position angle, rotation velocity and inclination, to describe galaxies. TiRiFiC works by directly fitting tilted-ring models to spectroscopic data cubes and hence is not affected by beam smearing or line-of-site-effects, e.g. strong warps. Because of that, the method is unavoidable as an analytic method in future Hi surveys. In the current implementation, though, there are several drawbacks. The implemented optimisers search for local solutions in parameter space only, do not quantify correlations between parameters and cannot find errors of single parameters. In theory, these drawbacks can be overcome by using Bayesian statistics, implemented in Multinest (Feroz et al. 2008), as it allows for sampling a posterior distribution irrespective of its multimodal nature resulting in parameter samples that correspond to the maximum in the posterior distribution. These parameter samples can be used as well to quantify correlations and find errors of single parameters. Since this method employs Bayesian statistics, it also allows the user to leverage any prior information they may have on parameter values.
- Full Text:
- Date Issued: 2020
- Authors: Maina, Eric Kamau
- Date: 2020
- Subjects: Bayesian statistical decision theory , Galaxies , Radio astronomy , TiRiFiC (Tilted Ring Fitting Code) , Neutral hydrogen , Spectroscopic data cubes , Galaxy parametrisation
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145783 , vital:38466
- Description: The orbits of neutral hydrogen (H I) gas found in most disk galaxies are circular and also exhibit long-lived warps at large radii where the restoring gravitational forces of the inner disk become weak (Spekkens and Giovanelli 2006). These warps make the tilted-ring model an ideal choice for galaxy parametrisation. Analysis software utilizing the tilted-ring-model can be grouped into two and three-dimensional based software. Józsa et al. (2007b) demonstrated that three dimensional based software is better suited for galaxy parametrisation because it is affected by the effect of beam smearing only by increasing the uncertainty of parameters but not with the notorious systematic effects observed for two-dimensional fitting techniques. TiRiFiC, The Tilted Ring Fitting Code (Józsa et al. 2007b), is a software to construct parameterised models of high-resolution data cubes of rotating galaxies. It uses the tilted-ring model, and with that, a combination of some parameters such as surface brightness, position angle, rotation velocity and inclination, to describe galaxies. TiRiFiC works by directly fitting tilted-ring models to spectroscopic data cubes and hence is not affected by beam smearing or line-of-site-effects, e.g. strong warps. Because of that, the method is unavoidable as an analytic method in future Hi surveys. In the current implementation, though, there are several drawbacks. The implemented optimisers search for local solutions in parameter space only, do not quantify correlations between parameters and cannot find errors of single parameters. In theory, these drawbacks can be overcome by using Bayesian statistics, implemented in Multinest (Feroz et al. 2008), as it allows for sampling a posterior distribution irrespective of its multimodal nature resulting in parameter samples that correspond to the maximum in the posterior distribution. These parameter samples can be used as well to quantify correlations and find errors of single parameters. Since this method employs Bayesian statistics, it also allows the user to leverage any prior information they may have on parameter values.
- Full Text:
- Date Issued: 2020
Nest site fidelity and nest site selection of loggerhead, Caretta Caretta, and leatherback, dermochelys coriacea, turtles in KwaZulu-Natal, South Africa
- Authors: Botha, Marié
- Date: 2010
- Subjects: Sea turtles -- South Africa -- KwaZulu-Natal , Loggerhead turtle -- South Africa -- KwaZulu-Natal , Leatherback turtle -- South Africa -- KwaZulu-Natal , Nest building , Turtles -- Habitat
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10696 , http://hdl.handle.net/10948/1233 , Sea turtles -- South Africa -- KwaZulu-Natal , Loggerhead turtle -- South Africa -- KwaZulu-Natal , Leatherback turtle -- South Africa -- KwaZulu-Natal , Nest building , Turtles -- Habitat
- Description: Loggerhead and leatherback sea turtles nest on the beaches of the north-eastern portion of Kwazulu-Natal within the iSimangaliso Wetland Park. Loggerheads place ~60 percent of all nests within an 8 km stretch of beach, whereas leatherbacks tend to space their nests more evenly along the entire length of the monitoring area. The study aimed to determine nest site fidelity of loggerheads and leatherbacks (using four decades of nesting data housed by Ezemvelo KZN Wildlife) and the factors that influence nest site selection of both species within the 56 km of turtle monitoring area (32N to 100S) and the 5 km area of high-density loggerhead nesting (0N to 12N). The effectiveness of nest site selection was then determined through the hatching success of loggerheads over the 5km area (0N to 12N). Results showed that loggerheads show a high degree of nest site fidelity (~3 km) with nest site fidelity of individuals increasing over subsequent seasons of nesting, as well as these individuals using the same stretches of beach for nesting (the most popular area being 1N to 4N for repeat nesters). Leatherbacks displayed nest site fidelity of ~9 km and this did not increase over successive seasons of nesting. In terms of nest site selection, loggerheads and leatherbacks both avoided areas where low shore rock was present, whereas both species preferred nesting on beaches of intermediate morphodynamic state. Leatherback nesting was significantly higher in areas with wider surf zones. Both species were able to surpass the high water mark when nesting as nests below this point would be almost certainly doomed. Hatching success of loggerheads was comparative to high (83 %) relative to other studies, however, nest success varied across the beach from beacon 1N to 12N. Areas where highest nest success was observed were not areas of highest nest density presumably due to artificial lighting. Results from this study increase our understanding of the evolutionary biology of loggerhead and leatherback turtles in South Africa and the effectiveness of loggerhead nest site selection through hatching success.
- Full Text:
- Date Issued: 2010
- Authors: Botha, Marié
- Date: 2010
- Subjects: Sea turtles -- South Africa -- KwaZulu-Natal , Loggerhead turtle -- South Africa -- KwaZulu-Natal , Leatherback turtle -- South Africa -- KwaZulu-Natal , Nest building , Turtles -- Habitat
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10696 , http://hdl.handle.net/10948/1233 , Sea turtles -- South Africa -- KwaZulu-Natal , Loggerhead turtle -- South Africa -- KwaZulu-Natal , Leatherback turtle -- South Africa -- KwaZulu-Natal , Nest building , Turtles -- Habitat
- Description: Loggerhead and leatherback sea turtles nest on the beaches of the north-eastern portion of Kwazulu-Natal within the iSimangaliso Wetland Park. Loggerheads place ~60 percent of all nests within an 8 km stretch of beach, whereas leatherbacks tend to space their nests more evenly along the entire length of the monitoring area. The study aimed to determine nest site fidelity of loggerheads and leatherbacks (using four decades of nesting data housed by Ezemvelo KZN Wildlife) and the factors that influence nest site selection of both species within the 56 km of turtle monitoring area (32N to 100S) and the 5 km area of high-density loggerhead nesting (0N to 12N). The effectiveness of nest site selection was then determined through the hatching success of loggerheads over the 5km area (0N to 12N). Results showed that loggerheads show a high degree of nest site fidelity (~3 km) with nest site fidelity of individuals increasing over subsequent seasons of nesting, as well as these individuals using the same stretches of beach for nesting (the most popular area being 1N to 4N for repeat nesters). Leatherbacks displayed nest site fidelity of ~9 km and this did not increase over successive seasons of nesting. In terms of nest site selection, loggerheads and leatherbacks both avoided areas where low shore rock was present, whereas both species preferred nesting on beaches of intermediate morphodynamic state. Leatherback nesting was significantly higher in areas with wider surf zones. Both species were able to surpass the high water mark when nesting as nests below this point would be almost certainly doomed. Hatching success of loggerheads was comparative to high (83 %) relative to other studies, however, nest success varied across the beach from beacon 1N to 12N. Areas where highest nest success was observed were not areas of highest nest density presumably due to artificial lighting. Results from this study increase our understanding of the evolutionary biology of loggerhead and leatherback turtles in South Africa and the effectiveness of loggerhead nest site selection through hatching success.
- Full Text:
- Date Issued: 2010
Time-activity budgets of cape gannets (Morus Capensis) at Bird Island, Algoa Bay
- Authors: Rishworth, Gavin Midgley
- Date: 2014
- Subjects: Birds of prey -- Behavior -- South Africa -- Algoa Bay , Gannets -- South Africa -- Algoa Bay , Birds -- Breeding -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10728 , http://hdl.handle.net/10948/d1021046
- Description: For several decades now, seabirds have been considered to be useful indicators of the state of their prey resources because of how they reflect lower-level trophic variability through proxies such as diet or behaviour. However, collection of appropriate data is often challenging in the marine environment because of logistical or financial constraints. In this study, time-activity budgets were studied in the Cape gannet (Morus capensis), a seabird which has been advocated as a potential bioindicator for local epipelagic prey. VHF transmitters attached to PVC leg-rings were fitted to 50 adult breeding pairs during the 2011/2012 and 2012/2013 breeding seasons at Bird Island, Algoa Bay, to determine whether an automated method of continuously collecting time-activity budget data can replace conventional laborious direct observations. To validate that the foraging trip duration data generated from the automated method was a reflection of foraging effort, Time-Depth Recorders (TDRs) were simultaneously equipped to birds with VHF transmitters for three weeks. In order to assess the influence of factors other than prey availability on parent time-activity budgets, sex, chick age and body condition were measured. Additionally, chick growth and survival were recorded in order to investigate the gender-specific effects of parental time-activity budget variability on these parameters. Attachment of VHF transmitters to leg-rings of adult Cape gannets had no observable negative effects on the adults or their chicks in terms of adult body condition, nest attendance and foraging trip durations, or chick growth and survival. Furthermore, the frequency distribution of behaviour bout (foraging trip and nest attendance) durations was no different between automated and directly observed data. However, the automated method did record shorter behaviour bouts, largely attributed to the increased likelihood of direct observations missing birds returning briefly to their nests during older chick provisioning. Additionally, foraging trip duration was highly correlated to foraging effort in terms of time spent resting on the sea surface, flying and diving. The automated method therefore appears to be a good reflection of direct nest attendance observations and foraging effort. Cape gannet time-activity budgets were related to chick age and parental sex. Especially as chicks neared fledging, females spent significantly longer periods of time foraging than males, with males consequently provisioning their chicks more often. Furthermore, adults departing their nests earlier spent more time away from the nest foraging as more same-day daylight hours were available. Chick growth was a function of parent foraging trip duration and associated prey delivery rates. Chick survival was most strongly affected by the amount of time which chicks were left unattended by both parents and consequently exposed to predation by kelp gulls (Larus dominicanus) or to adverse weather conditions. Additionally, for females (but not males) there appeared to be a trade-off between foraging trip duration and chick survival. The Cape gannet appears to demonstrate a strategy whereby the costs of reproduction to the female are shifted towards male-dominated chick provisioning as the chick nears fledging. Drivers of time-activity budget variability such as chick age and parental sex therefore need to be considered if using data on foraging trip duration as a proxy of foraging effort and prey availability.
- Full Text:
- Date Issued: 2014
- Authors: Rishworth, Gavin Midgley
- Date: 2014
- Subjects: Birds of prey -- Behavior -- South Africa -- Algoa Bay , Gannets -- South Africa -- Algoa Bay , Birds -- Breeding -- South Africa -- Algoa Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10728 , http://hdl.handle.net/10948/d1021046
- Description: For several decades now, seabirds have been considered to be useful indicators of the state of their prey resources because of how they reflect lower-level trophic variability through proxies such as diet or behaviour. However, collection of appropriate data is often challenging in the marine environment because of logistical or financial constraints. In this study, time-activity budgets were studied in the Cape gannet (Morus capensis), a seabird which has been advocated as a potential bioindicator for local epipelagic prey. VHF transmitters attached to PVC leg-rings were fitted to 50 adult breeding pairs during the 2011/2012 and 2012/2013 breeding seasons at Bird Island, Algoa Bay, to determine whether an automated method of continuously collecting time-activity budget data can replace conventional laborious direct observations. To validate that the foraging trip duration data generated from the automated method was a reflection of foraging effort, Time-Depth Recorders (TDRs) were simultaneously equipped to birds with VHF transmitters for three weeks. In order to assess the influence of factors other than prey availability on parent time-activity budgets, sex, chick age and body condition were measured. Additionally, chick growth and survival were recorded in order to investigate the gender-specific effects of parental time-activity budget variability on these parameters. Attachment of VHF transmitters to leg-rings of adult Cape gannets had no observable negative effects on the adults or their chicks in terms of adult body condition, nest attendance and foraging trip durations, or chick growth and survival. Furthermore, the frequency distribution of behaviour bout (foraging trip and nest attendance) durations was no different between automated and directly observed data. However, the automated method did record shorter behaviour bouts, largely attributed to the increased likelihood of direct observations missing birds returning briefly to their nests during older chick provisioning. Additionally, foraging trip duration was highly correlated to foraging effort in terms of time spent resting on the sea surface, flying and diving. The automated method therefore appears to be a good reflection of direct nest attendance observations and foraging effort. Cape gannet time-activity budgets were related to chick age and parental sex. Especially as chicks neared fledging, females spent significantly longer periods of time foraging than males, with males consequently provisioning their chicks more often. Furthermore, adults departing their nests earlier spent more time away from the nest foraging as more same-day daylight hours were available. Chick growth was a function of parent foraging trip duration and associated prey delivery rates. Chick survival was most strongly affected by the amount of time which chicks were left unattended by both parents and consequently exposed to predation by kelp gulls (Larus dominicanus) or to adverse weather conditions. Additionally, for females (but not males) there appeared to be a trade-off between foraging trip duration and chick survival. The Cape gannet appears to demonstrate a strategy whereby the costs of reproduction to the female are shifted towards male-dominated chick provisioning as the chick nears fledging. Drivers of time-activity budget variability such as chick age and parental sex therefore need to be considered if using data on foraging trip duration as a proxy of foraging effort and prey availability.
- Full Text:
- Date Issued: 2014
The biology of suburban olive thrushes (Turdus olivaceus olivaceus) in the Eastern Cape, South Africa
- Authors: Bonnevie, Bo Tørris
- Date: 2005
- Subjects: Thrushes , Turdus , Thrushes -- South Africa -- Eastern Cape , Turdus -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5651 , http://hdl.handle.net/10962/d1005333 , Thrushes , Turdus , Thrushes -- South Africa -- Eastern Cape , Turdus -- South Africa -- Eastern Cape
- Description: This study investigated the biology of the Olive Thrush Turdus olivaceus olivaceus in Grahamstown, South Africa from 1998 to 2003. Behavioural differences between males and females, parent-young interactions, development of fledglings, and the role of song and moult in territorial behaviour were investigated. Comparisons of biometrics, moult and survival were made using Olive Thrush ringing data from other regions. There were no significant differences in mass, wing length or survival rate between the Eastern and Western Cape provinces, but primary wing moult started earlier in the Western Cape and coincided with the end of the main breeding periods in both provinces. Both males and females of breeding pairs remained in and defended their territories throughout the year, but there was some evidence that territorial defence was strongest during the breeding periods. Roughly, every 100 eggs laid produce 50 fledglings. Out of these 20 to 30 reach the age of independence at approximately 50 days, and only five of these juvenile birds reach maturity. Adult survival was estimated at 80%, with a mean life expectancy of 4.5 years and a conservative estimate of maximum lifespan of 11 years. Using ringing data and museum specimens, the Olive Thrush was compared with the Karoo Thrush Turdus smithi, a former race of the Olive Thrush. Olive Thrushes had shorter bills and wings, but were heavier than Karoo Thrushes from the Cradock district. There were also differences in bill and eye-ring colouration between these populations. No morphological differences were found between the sexes in either species.
- Full Text:
- Date Issued: 2005
- Authors: Bonnevie, Bo Tørris
- Date: 2005
- Subjects: Thrushes , Turdus , Thrushes -- South Africa -- Eastern Cape , Turdus -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5651 , http://hdl.handle.net/10962/d1005333 , Thrushes , Turdus , Thrushes -- South Africa -- Eastern Cape , Turdus -- South Africa -- Eastern Cape
- Description: This study investigated the biology of the Olive Thrush Turdus olivaceus olivaceus in Grahamstown, South Africa from 1998 to 2003. Behavioural differences between males and females, parent-young interactions, development of fledglings, and the role of song and moult in territorial behaviour were investigated. Comparisons of biometrics, moult and survival were made using Olive Thrush ringing data from other regions. There were no significant differences in mass, wing length or survival rate between the Eastern and Western Cape provinces, but primary wing moult started earlier in the Western Cape and coincided with the end of the main breeding periods in both provinces. Both males and females of breeding pairs remained in and defended their territories throughout the year, but there was some evidence that territorial defence was strongest during the breeding periods. Roughly, every 100 eggs laid produce 50 fledglings. Out of these 20 to 30 reach the age of independence at approximately 50 days, and only five of these juvenile birds reach maturity. Adult survival was estimated at 80%, with a mean life expectancy of 4.5 years and a conservative estimate of maximum lifespan of 11 years. Using ringing data and museum specimens, the Olive Thrush was compared with the Karoo Thrush Turdus smithi, a former race of the Olive Thrush. Olive Thrushes had shorter bills and wings, but were heavier than Karoo Thrushes from the Cradock district. There were also differences in bill and eye-ring colouration between these populations. No morphological differences were found between the sexes in either species.
- Full Text:
- Date Issued: 2005
Philosophy: PHL 223
- Authors: Van der Nest, M
- Date: 2011-11
- Language: English
- Type: Examination paper
- Identifier: vital:18238 , http://hdl.handle.net/10353/d1011230
- Description: Philosophy: PHL 223, supplementary examination November 2011.
- Full Text: false
- Date Issued: 2011-11
- Authors: Van der Nest, M
- Date: 2011-11
- Language: English
- Type: Examination paper
- Identifier: vital:18238 , http://hdl.handle.net/10353/d1011230
- Description: Philosophy: PHL 223, supplementary examination November 2011.
- Full Text: false
- Date Issued: 2011-11
Reproductive behaviour of the skunk clownfish, Amphiprion akallopisos, under captive conditions
- Authors: Haschick, Rory Dean
- Date: 1998
- Subjects: Anemonefishes -- Spawning , Amphiprion -- Reproduction , Fishes -- Reproduction , Hatchery fishes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5316 , http://hdl.handle.net/10962/d1005161 , Anemonefishes -- Spawning , Amphiprion -- Reproduction , Fishes -- Reproduction , Hatchery fishes
- Description: The objectives of the study were to determine whether or not behaviour could be used to predict spawning in Amphiprion akallopisos, and to document the behaviour of this species under various environmental conditions in captivity. The spawning behaviour of A. akallopisos was studied and quantified. Three behaviour patterns - belly touching, nest cleaning by the female and mutual nest cleaning (by the male and the female) were identified as predictors for spawning. The reproductive behaviour of A.akallopisos under three photoperiods was investigated. The photoperiods were: 14L:10D, 10hr15minL:13hr45minD and a natural photoperiod cycle condensed into three months. A. akallopisos maintained under 14 L:10D exhibited a significantly higher frequency and duration of chasing, nest cleaning and total interaction compared to fish kept under 10hr15minL:13hr45minD. A photoperiod of 14L:10D was selected for further studies. As manipulation of photoperiod did not induce spawning, GnRHa was administered to the fish in the diet at levels of 10, 20, 40 and 80 μg/kg BW. Control groups were fed untreated food. None of the dosages were successful in inducing spawning, or spawning behaviour in A. akallopisos. It is possible that the method of hormone application was not suitable for this species. It is also possible that behaviour may regulate blood hormone levels as opposed to endocrine status influencing behaviour. In the third trial, A. akallopisos was maintained with, and without sea anemones in order to determine whether or not anemone hosts are necessary for spawning. The presence of anemones did not induce spawning and A. akallopisos kept without anemones exhibited significantly more interactive behaviour than fish kept with hosts. Spawning of A. akallopisos at a later date without anemones suggests that anemones are not necessary for spawning in A. akallopisos. Light intensity was investigated as a cue for spawning. The reproductive behaviour of A. akallopisos was then studied under light intensities of 4.16 x 10¹⁵ quanta.sec⁻¹.cm⁻², 8.85 x 10¹⁵ quanta.sec⁻¹.cm⁻² and this intensity plus natural light. Spawning occurred mainly under 8.85 x 10¹⁵ quanta.sec⁻¹.cm⁻². Fish maintained under this light intensity exhibited significantly more of nest cleaning behaviour in terms of frequency and duration than fish maintained under low light intensity. A minimum light intensity of 8.85 x 10¹⁵ quanta. sec⁻¹.cm⁻² is recommended for conditioning of this species. This study can be of practical relevance to hatchery managers who can use the methods developed and record predictors for spawning in A. akallopisos and other Amphiprion species. In this way imminence of spawning may be estimated. Most importantly, the study also has academic merit as little work has been undertaken in this field. Although the observational method used in this study was adequate for the purposes of the investigation, future work of this nature should incorporate other methods of documenting gonadal development such as gonadal staging and GSI in order to obtain more conclusive results.
- Full Text:
- Date Issued: 1998
- Authors: Haschick, Rory Dean
- Date: 1998
- Subjects: Anemonefishes -- Spawning , Amphiprion -- Reproduction , Fishes -- Reproduction , Hatchery fishes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5316 , http://hdl.handle.net/10962/d1005161 , Anemonefishes -- Spawning , Amphiprion -- Reproduction , Fishes -- Reproduction , Hatchery fishes
- Description: The objectives of the study were to determine whether or not behaviour could be used to predict spawning in Amphiprion akallopisos, and to document the behaviour of this species under various environmental conditions in captivity. The spawning behaviour of A. akallopisos was studied and quantified. Three behaviour patterns - belly touching, nest cleaning by the female and mutual nest cleaning (by the male and the female) were identified as predictors for spawning. The reproductive behaviour of A.akallopisos under three photoperiods was investigated. The photoperiods were: 14L:10D, 10hr15minL:13hr45minD and a natural photoperiod cycle condensed into three months. A. akallopisos maintained under 14 L:10D exhibited a significantly higher frequency and duration of chasing, nest cleaning and total interaction compared to fish kept under 10hr15minL:13hr45minD. A photoperiod of 14L:10D was selected for further studies. As manipulation of photoperiod did not induce spawning, GnRHa was administered to the fish in the diet at levels of 10, 20, 40 and 80 μg/kg BW. Control groups were fed untreated food. None of the dosages were successful in inducing spawning, or spawning behaviour in A. akallopisos. It is possible that the method of hormone application was not suitable for this species. It is also possible that behaviour may regulate blood hormone levels as opposed to endocrine status influencing behaviour. In the third trial, A. akallopisos was maintained with, and without sea anemones in order to determine whether or not anemone hosts are necessary for spawning. The presence of anemones did not induce spawning and A. akallopisos kept without anemones exhibited significantly more interactive behaviour than fish kept with hosts. Spawning of A. akallopisos at a later date without anemones suggests that anemones are not necessary for spawning in A. akallopisos. Light intensity was investigated as a cue for spawning. The reproductive behaviour of A. akallopisos was then studied under light intensities of 4.16 x 10¹⁵ quanta.sec⁻¹.cm⁻², 8.85 x 10¹⁵ quanta.sec⁻¹.cm⁻² and this intensity plus natural light. Spawning occurred mainly under 8.85 x 10¹⁵ quanta.sec⁻¹.cm⁻². Fish maintained under this light intensity exhibited significantly more of nest cleaning behaviour in terms of frequency and duration than fish maintained under low light intensity. A minimum light intensity of 8.85 x 10¹⁵ quanta. sec⁻¹.cm⁻² is recommended for conditioning of this species. This study can be of practical relevance to hatchery managers who can use the methods developed and record predictors for spawning in A. akallopisos and other Amphiprion species. In this way imminence of spawning may be estimated. Most importantly, the study also has academic merit as little work has been undertaken in this field. Although the observational method used in this study was adequate for the purposes of the investigation, future work of this nature should incorporate other methods of documenting gonadal development such as gonadal staging and GSI in order to obtain more conclusive results.
- Full Text:
- Date Issued: 1998
The role of male competition and female choice in the mating success of a Lek-breeding Southern African Cichlid fish Pseudocrenilabrus Philander (Pisces: Cichlidae)
- Authors: Chan, Tin-Yam
- Date: 1988
- Subjects: Cichlids -- Africa, Southern -- Physiology Courtship in animals Fishes -- Reproduction Cichlids Pseudocrenilabrus philander Lek-breeding Courtship Reproduction Spawning Competition Rivalry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5599 , http://hdl.handle.net/10962/d1002049
- Description: A lek-breeding cichlid fish Pseudocrenilabrus philander was studied experimentally. Females in choice-chamber experiments showed no active choice for male size and colour, or for other male attributes, but preferred males which courted most actively. In a laboratory lek, the significant determinants of the strongly skewed mating success in males were territory size, side-shake and female chasing frequency. Together these three variables explained 79% of the variation in male mating success, with territory size alone accounting for 75% of the variation and the other two variables each accounting for 2% of the remaining variation. As there was no difference in territory quality in the laboratory lek, territory size became the principal measure of the effect of male-male competition since it was directly related to dominance. Both side-shake and female chasing could be identified as the basic factors influencing female choice, as they had an immediate effect on the display-response mating system of females. Thus, the relative importance of these three variables indicated that sexual selection in this particular lek mating species operated chiefly through the agency of intrasexual competition for dominance. However, both female behaviour and their requirement for a prolonged pre-spawning courtship had the effect of promoting male rivalry and favouring mating with dominant males. Although the intense male competition excluded subordinate males from practising normal courtship behaviour, competitively inferior males might "make the best of a bad situation" by facultatively adopting an alternative sneaking tactic to gain access to females. Spawning intrusions by females to steal freshly-laid eggs also occurred frequently. However, territorial males appeared to be relatively more tolerant of female intruders than male sneakers. Interference during spawning could lead to a longer pre-spawning courtship and even multiple-mating by females. The results of the present study and the behavioural evidence shown by males and females did not support the ʺrunaway selection modelʺ of the mating pattern in terms of sexual selection in leks, but conformed to the rival ʺwar propaganda modelʺ
- Full Text:
- Date Issued: 1988
- Authors: Chan, Tin-Yam
- Date: 1988
- Subjects: Cichlids -- Africa, Southern -- Physiology Courtship in animals Fishes -- Reproduction Cichlids Pseudocrenilabrus philander Lek-breeding Courtship Reproduction Spawning Competition Rivalry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5599 , http://hdl.handle.net/10962/d1002049
- Description: A lek-breeding cichlid fish Pseudocrenilabrus philander was studied experimentally. Females in choice-chamber experiments showed no active choice for male size and colour, or for other male attributes, but preferred males which courted most actively. In a laboratory lek, the significant determinants of the strongly skewed mating success in males were territory size, side-shake and female chasing frequency. Together these three variables explained 79% of the variation in male mating success, with territory size alone accounting for 75% of the variation and the other two variables each accounting for 2% of the remaining variation. As there was no difference in territory quality in the laboratory lek, territory size became the principal measure of the effect of male-male competition since it was directly related to dominance. Both side-shake and female chasing could be identified as the basic factors influencing female choice, as they had an immediate effect on the display-response mating system of females. Thus, the relative importance of these three variables indicated that sexual selection in this particular lek mating species operated chiefly through the agency of intrasexual competition for dominance. However, both female behaviour and their requirement for a prolonged pre-spawning courtship had the effect of promoting male rivalry and favouring mating with dominant males. Although the intense male competition excluded subordinate males from practising normal courtship behaviour, competitively inferior males might "make the best of a bad situation" by facultatively adopting an alternative sneaking tactic to gain access to females. Spawning intrusions by females to steal freshly-laid eggs also occurred frequently. However, territorial males appeared to be relatively more tolerant of female intruders than male sneakers. Interference during spawning could lead to a longer pre-spawning courtship and even multiple-mating by females. The results of the present study and the behavioural evidence shown by males and females did not support the ʺrunaway selection modelʺ of the mating pattern in terms of sexual selection in leks, but conformed to the rival ʺwar propaganda modelʺ
- Full Text:
- Date Issued: 1988
Infant observation : the first year of life
- Authors: Gering, Jeanne
- Date: 2013-10-02
- Subjects: Infant psychology Parent and infant Interpersonal communication in infants Mother and infant
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3196 , http://hdl.handle.net/10962/d1009451
- Description: This research project is about infant-observation, that is looking at, observing, and studying parent-infant interactions and relationships within the first year of life. The principle intention of the study is to illustrate and shed light upon human infant development and how the newborn becomes a fully functioning member within the family. The study provides a context in which to consider parent-infant interaction beginning in utero, expanding to the birthing process, and continuing through the infant's first year. It focuses on specific themes of parent-infant interaction. The following situations are explored: the role of the mother; the mother as a container; the infant's experience of containment; the internalisation of experience; the symbolic meaning of food; dealing with distress and the development of concrete communication; the growth of a sense of ego; and, the infant's internal world. The study concludes by addressing various implications for further psychotherapy and compares the therapist-client relationship to the mother-infant relationship. The research outlines one particular psychoanalytic theoretical orientation of mental and emotional development. It is a model derived predominantly from The Developmental School Theorists and Object Relations Theorists, namely, Bowlby, Klein, Mahler and Winnicott. This model looks at the infant's earliest relationships and the processes these set up within the infant's developing mind. Infant observation, asa research method proposed by Bick and Sidoli, links method and theory, and serves as the methodological approach utilised in the present study. A video, based on the parent-infant interaction of three families, provides observational data and may be viewed in conjunction with this research. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Authors: Gering, Jeanne
- Date: 2013-10-02
- Subjects: Infant psychology Parent and infant Interpersonal communication in infants Mother and infant
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3196 , http://hdl.handle.net/10962/d1009451
- Description: This research project is about infant-observation, that is looking at, observing, and studying parent-infant interactions and relationships within the first year of life. The principle intention of the study is to illustrate and shed light upon human infant development and how the newborn becomes a fully functioning member within the family. The study provides a context in which to consider parent-infant interaction beginning in utero, expanding to the birthing process, and continuing through the infant's first year. It focuses on specific themes of parent-infant interaction. The following situations are explored: the role of the mother; the mother as a container; the infant's experience of containment; the internalisation of experience; the symbolic meaning of food; dealing with distress and the development of concrete communication; the growth of a sense of ego; and, the infant's internal world. The study concludes by addressing various implications for further psychotherapy and compares the therapist-client relationship to the mother-infant relationship. The research outlines one particular psychoanalytic theoretical orientation of mental and emotional development. It is a model derived predominantly from The Developmental School Theorists and Object Relations Theorists, namely, Bowlby, Klein, Mahler and Winnicott. This model looks at the infant's earliest relationships and the processes these set up within the infant's developing mind. Infant observation, asa research method proposed by Bick and Sidoli, links method and theory, and serves as the methodological approach utilised in the present study. A video, based on the parent-infant interaction of three families, provides observational data and may be viewed in conjunction with this research. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
Ecology and natural history of the Masarid wasps of the world with an assessment of their role as pollinators in southern Africa (Hymenoptera : Vespoidea : Masaridae)
- Authors: Gess, Sarah Kathleen
- Date: 1993
- Subjects: Wasps -- Ecology Pollen wasps -- Ecology Vespidae -- Ecology Pollination by insects -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5669 , http://hdl.handle.net/10962/d1005354
- Description: The worldwide knowledge of the ecology and natural history of the masarid wasps, those wasps which bee-like provision their nest cells with pollen and nectar, is synthesized and discussed putting into context the investigations concerning nesting and flower visiting by southern African masarids conducted by the present author. Masarids are found mostly to favour warm to hot areas with relatively low rainfall and open scrubby vegetation. At the generic level the masarids of the Nearctic, Neotropical and Australian regions are distinct from each other and from those of the Palaearctic and Afrotropical regions combined. No species are shared between regions. Southern Africa is apparently the area of greatest species diversity. In this region, at least, there is a high incidence of narrow endemism. Masarids are associated with a relatively small range of plant families. Where sufficient records are available distinct major preferences are shown between zoogeographical regions. Relatedness of plant preferences between zoogeographical regions is apparent when relatedness of plant taxa is considered. Within a region there is marked overlap in masarid generic preferences for flower families. At the specific level there is marked oligolecty and narrow polylecty. The majority of nesting studies indicate that nest construction, egg laying and provisioning are performed by a single female per nest, however, nest sharing has been alledged for two species. No parasitic masarids have been recorded. Egg laying precedes provisioning. Mass provisioning is the rule. According to species, nests are sited in the ground, in non-friable soil or friable soil, in earthen vertical banks, on stones or on plants. Seven nest types are defined. Three bonding agents, water, nectar and self-generated silk are used. Masarids are evaluated as potential pollinators of their forage plants in southern Africa. The "masarid pollination syndrome", though less broad is shown to fall within that designated melittophily. The case studies considered make it clear that, whereas the masarids visiting some flower groups are members of a guild of potential pollinators, the masarids visiting others are probably their most important pollinators. Increasing land utilization is shown to threaten the existence of narrowly endmic masarid species.
- Full Text:
- Date Issued: 1993
- Authors: Gess, Sarah Kathleen
- Date: 1993
- Subjects: Wasps -- Ecology Pollen wasps -- Ecology Vespidae -- Ecology Pollination by insects -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5669 , http://hdl.handle.net/10962/d1005354
- Description: The worldwide knowledge of the ecology and natural history of the masarid wasps, those wasps which bee-like provision their nest cells with pollen and nectar, is synthesized and discussed putting into context the investigations concerning nesting and flower visiting by southern African masarids conducted by the present author. Masarids are found mostly to favour warm to hot areas with relatively low rainfall and open scrubby vegetation. At the generic level the masarids of the Nearctic, Neotropical and Australian regions are distinct from each other and from those of the Palaearctic and Afrotropical regions combined. No species are shared between regions. Southern Africa is apparently the area of greatest species diversity. In this region, at least, there is a high incidence of narrow endemism. Masarids are associated with a relatively small range of plant families. Where sufficient records are available distinct major preferences are shown between zoogeographical regions. Relatedness of plant preferences between zoogeographical regions is apparent when relatedness of plant taxa is considered. Within a region there is marked overlap in masarid generic preferences for flower families. At the specific level there is marked oligolecty and narrow polylecty. The majority of nesting studies indicate that nest construction, egg laying and provisioning are performed by a single female per nest, however, nest sharing has been alledged for two species. No parasitic masarids have been recorded. Egg laying precedes provisioning. Mass provisioning is the rule. According to species, nests are sited in the ground, in non-friable soil or friable soil, in earthen vertical banks, on stones or on plants. Seven nest types are defined. Three bonding agents, water, nectar and self-generated silk are used. Masarids are evaluated as potential pollinators of their forage plants in southern Africa. The "masarid pollination syndrome", though less broad is shown to fall within that designated melittophily. The case studies considered make it clear that, whereas the masarids visiting some flower groups are members of a guild of potential pollinators, the masarids visiting others are probably their most important pollinators. Increasing land utilization is shown to threaten the existence of narrowly endmic masarid species.
- Full Text:
- Date Issued: 1993
Environmental cues and sensory preferences directing the nesting process in loggerhead turtles, caretta caretta, nesting in Maputaland, South Africa
- Authors: Brazier, Wayne
- Date: 2012
- Subjects: Sea turtles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10721 , http://hdl.handle.net/10948/d1015688
- Description: Animals use their senses for everything on an immediate, and day to day fashion – detecting danger, finding food, finding mates among other activities. In sea turtles and other migratory species senses are used for long-distance migrations. Senses such as smell, vision and hearing, have been studied experimentally under laboratory conditions but seldom have been investigated in the field. This thesis takes a combination of field and laboratory experiments and investigates some of the hypotheses involved in natal homing and nest site selection. The loggerhead’s nesting distribution in Maputaland is distinct with characteristic high and low density nesting areas which are consistent from year to year. Investigations by earlier researchers on these beaches suggested that beach characteristics, such as beach morphodynamic type and beach width, do not appear to influence the beaches at which loggerheads emerge to nest. The high density nesting area (with approximately 440 loggerhead emergences/km) have similar beach characteristics as the low density nesting area (with <50 loggerhead emergences/km). It is therefore suggested that there is another cue that drives nest site selection. It can either be related to a physical characteristic not yet realised, or is a non-physical (but chemical or biological) cue. This dissertation aims to identify the sensory inputs received during the nest selection process, as well as sea-finding ability after nesting. To investigate the mechanism causing the high-density as opposed to the low-density nesting area, three potential drivers were investigated namely: chemical imprinting (as a natal beach cue), ambient and artificial light (as deterrents) and social facilitation (as a learned behaviour). It was also attempted to identify the strength of the most common senses – vision, hearing and smell. As animal ethics restricts interfering with emerging or nesting turtles, the strengths of these senses were tested during sea-finding by adult loggerheads. The results indicate that sulfide concentrations appear to be used as chemical cues for nesting as these concentrations are elevated (>150 percent) in the high density nesting beaches compared to the low density nesting beaches within and among seasons however further investigations are required. Artificial light (range: 0.045–0.5 lux) is an active deterrent of female emergences while ambient light, even under extreme conditions such as lightning during electric storms (up to 8.2 lux), appears to have no observable influence on the spatial or temporal distributions of emergences. Social facilitation appears unlikely as a primary nest site selection factor for loggerheads. It may however, play a minor secondary role to preferred areas or hotspots. Sea-finding in post-nesting female loggerheads appears to be driven exclusively by visual cues such as the light horizon, with minimal to no influence from other cues (the sound of the breakers, slope or smell of the ocean) which solidify the visual system’s use in sea-finding. This research on the nest site selection of loggerheads and the sensory systems involved in this process has added valuable information to the limited pool of knowledge already present and has created a solid framework on which further investigations can be based. Future work in this field should focus on integrating a suite of sensory stimuli and cues to receive a greater understanding of the sensory systems used in nest site selection.
- Full Text:
- Date Issued: 2012
- Authors: Brazier, Wayne
- Date: 2012
- Subjects: Sea turtles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10721 , http://hdl.handle.net/10948/d1015688
- Description: Animals use their senses for everything on an immediate, and day to day fashion – detecting danger, finding food, finding mates among other activities. In sea turtles and other migratory species senses are used for long-distance migrations. Senses such as smell, vision and hearing, have been studied experimentally under laboratory conditions but seldom have been investigated in the field. This thesis takes a combination of field and laboratory experiments and investigates some of the hypotheses involved in natal homing and nest site selection. The loggerhead’s nesting distribution in Maputaland is distinct with characteristic high and low density nesting areas which are consistent from year to year. Investigations by earlier researchers on these beaches suggested that beach characteristics, such as beach morphodynamic type and beach width, do not appear to influence the beaches at which loggerheads emerge to nest. The high density nesting area (with approximately 440 loggerhead emergences/km) have similar beach characteristics as the low density nesting area (with <50 loggerhead emergences/km). It is therefore suggested that there is another cue that drives nest site selection. It can either be related to a physical characteristic not yet realised, or is a non-physical (but chemical or biological) cue. This dissertation aims to identify the sensory inputs received during the nest selection process, as well as sea-finding ability after nesting. To investigate the mechanism causing the high-density as opposed to the low-density nesting area, three potential drivers were investigated namely: chemical imprinting (as a natal beach cue), ambient and artificial light (as deterrents) and social facilitation (as a learned behaviour). It was also attempted to identify the strength of the most common senses – vision, hearing and smell. As animal ethics restricts interfering with emerging or nesting turtles, the strengths of these senses were tested during sea-finding by adult loggerheads. The results indicate that sulfide concentrations appear to be used as chemical cues for nesting as these concentrations are elevated (>150 percent) in the high density nesting beaches compared to the low density nesting beaches within and among seasons however further investigations are required. Artificial light (range: 0.045–0.5 lux) is an active deterrent of female emergences while ambient light, even under extreme conditions such as lightning during electric storms (up to 8.2 lux), appears to have no observable influence on the spatial or temporal distributions of emergences. Social facilitation appears unlikely as a primary nest site selection factor for loggerheads. It may however, play a minor secondary role to preferred areas or hotspots. Sea-finding in post-nesting female loggerheads appears to be driven exclusively by visual cues such as the light horizon, with minimal to no influence from other cues (the sound of the breakers, slope or smell of the ocean) which solidify the visual system’s use in sea-finding. This research on the nest site selection of loggerheads and the sensory systems involved in this process has added valuable information to the limited pool of knowledge already present and has created a solid framework on which further investigations can be based. Future work in this field should focus on integrating a suite of sensory stimuli and cues to receive a greater understanding of the sensory systems used in nest site selection.
- Full Text:
- Date Issued: 2012
Penguin parenting : assortative mating, nest attendance and sex-specific chick provisioning in the African Penguin (Spheniscus demersus)
- Authors: Smith, Diane Lauren
- Date: 2016
- Subjects: African penguin , Penguins -- South Africa , Penguins -- Sexual behavior , Parental behavior in animals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5943 , http://hdl.handle.net/10962/d1019993
- Description: Animal behaviour is especially sensitive to environmental variability and prey availability during the breeding season, and this is particularly true for non-volant, central place foragers such as the endangered African Penguin (Spheniscus demersus). Individual sex and morphology, as well as the level of assortment within mated pairs can influence both the behaviour and the reproductive success of species exhibiting biparental care. This study made use of a large biometric database and nest attendance video footage to determine the influence of intrinsic (assortative mating, brood size and chick age) and extrinsic (environmental conditions, anthropic disturbance) factors on breeding behaviour and performance of African Penguins on Bird Island, Algoa Bay, during peak breeding (March - July) in 2013. While sexual dimorphism in African Penguins is subtle, the colony-specific discriminant functions presented here provide an accurate sexing tool when only bill and flipper length are available. Despite the premise that selection of a large, high-quality mate in this longlived, monogamous seabird governs lifetime fitness, only low levels of assortative mating were found, and this only for earlier breeders, when larger females (but not males) bred. The 2013 season was a particularly successful one, coinciding with above-average sardine and anchovy abundance, and almost 80 percent of monitored nests were double-brooded, with very low levels of mortality. A- and B-chicks of double broods and singleton chicks grew at similar rates and exhibited similar body condition indices. In these conditions, chick developmental rates were independent of parental size, assortment or provisioning behaviour. Females raising a double brood were significantly lighter and in poorer body condition than those raising a single chick, although the same trend was not evident in males. Offspring sex ratio in 2013 (2.27:1) favoured male chicks, suggesting that there is potential to over-produce the larger sex when resources are plentiful. Peak nest arrival and departure times of parents did not change over the course of monitored breeding attempts (March-June), nor were they different for disturbed and undisturbed nests or for a single or double brood. The increase in CCTV-observed provisioning rate as chicks grew larger was best explained by brood size, at-sea chlorophyll a concentration, and maximum air temperature, but was unrelated to parental morphology or assortative index. Importantly, parental absenteeism commenced earlier and was markedly greater in nests frequently handled by researchers than in undisturbed nests. Both the time spent together by parents, and absenteeism were measurably affected by maximum afternoon air temperatures, the effects of which are expected to be exacerbated by poorer foraging conditions and climate change. A third of manually-monitored nests shared chick-guarding duties unequally, although this phenomenon was independent of parental sex or morphology. The adaptive benefits of mating patterns and division of labour during chick-rearing may only become apparent in a year of below-average food availability and it is highly recommended that this study be repeated in a year of scarce food resources. These findings augment past foraging ecology studies and demonstrate that investigator disturbance and environmental conditions can affect the nesting behaviour of this highly threatened seabird.
- Full Text:
- Date Issued: 2016
- Authors: Smith, Diane Lauren
- Date: 2016
- Subjects: African penguin , Penguins -- South Africa , Penguins -- Sexual behavior , Parental behavior in animals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5943 , http://hdl.handle.net/10962/d1019993
- Description: Animal behaviour is especially sensitive to environmental variability and prey availability during the breeding season, and this is particularly true for non-volant, central place foragers such as the endangered African Penguin (Spheniscus demersus). Individual sex and morphology, as well as the level of assortment within mated pairs can influence both the behaviour and the reproductive success of species exhibiting biparental care. This study made use of a large biometric database and nest attendance video footage to determine the influence of intrinsic (assortative mating, brood size and chick age) and extrinsic (environmental conditions, anthropic disturbance) factors on breeding behaviour and performance of African Penguins on Bird Island, Algoa Bay, during peak breeding (March - July) in 2013. While sexual dimorphism in African Penguins is subtle, the colony-specific discriminant functions presented here provide an accurate sexing tool when only bill and flipper length are available. Despite the premise that selection of a large, high-quality mate in this longlived, monogamous seabird governs lifetime fitness, only low levels of assortative mating were found, and this only for earlier breeders, when larger females (but not males) bred. The 2013 season was a particularly successful one, coinciding with above-average sardine and anchovy abundance, and almost 80 percent of monitored nests were double-brooded, with very low levels of mortality. A- and B-chicks of double broods and singleton chicks grew at similar rates and exhibited similar body condition indices. In these conditions, chick developmental rates were independent of parental size, assortment or provisioning behaviour. Females raising a double brood were significantly lighter and in poorer body condition than those raising a single chick, although the same trend was not evident in males. Offspring sex ratio in 2013 (2.27:1) favoured male chicks, suggesting that there is potential to over-produce the larger sex when resources are plentiful. Peak nest arrival and departure times of parents did not change over the course of monitored breeding attempts (March-June), nor were they different for disturbed and undisturbed nests or for a single or double brood. The increase in CCTV-observed provisioning rate as chicks grew larger was best explained by brood size, at-sea chlorophyll a concentration, and maximum air temperature, but was unrelated to parental morphology or assortative index. Importantly, parental absenteeism commenced earlier and was markedly greater in nests frequently handled by researchers than in undisturbed nests. Both the time spent together by parents, and absenteeism were measurably affected by maximum afternoon air temperatures, the effects of which are expected to be exacerbated by poorer foraging conditions and climate change. A third of manually-monitored nests shared chick-guarding duties unequally, although this phenomenon was independent of parental sex or morphology. The adaptive benefits of mating patterns and division of labour during chick-rearing may only become apparent in a year of below-average food availability and it is highly recommended that this study be repeated in a year of scarce food resources. These findings augment past foraging ecology studies and demonstrate that investigator disturbance and environmental conditions can affect the nesting behaviour of this highly threatened seabird.
- Full Text:
- Date Issued: 2016
Introduction to Philosophy: PHL 111
- Authors: Van der Nest, M , Louw, T
- Date: 2010-06
- Subjects: Philosophy
- Language: English
- Type: Examination paper
- Identifier: vital:18202 , http://hdl.handle.net/10353/d1011191
- Description: Introduction to Philosophy: PHL 111, supplementary examinations July 2010.
- Full Text: false
- Date Issued: 2010-06
- Authors: Van der Nest, M , Louw, T
- Date: 2010-06
- Subjects: Philosophy
- Language: English
- Type: Examination paper
- Identifier: vital:18202 , http://hdl.handle.net/10353/d1011191
- Description: Introduction to Philosophy: PHL 111, supplementary examinations July 2010.
- Full Text: false
- Date Issued: 2010-06
Kantian Philosophy: PHL 223
- Authors: Van der Nest, M , Louw, T
- Date: 2011-02
- Language: English
- Type: Examination paper
- Identifier: vital:18194 , http://hdl.handle.net/10353/d1011183
- Description: Kantian Philosophy: PHL 223, supplementary examination February 2011.
- Full Text: false
- Date Issued: 2011-02
- Authors: Van der Nest, M , Louw, T
- Date: 2011-02
- Language: English
- Type: Examination paper
- Identifier: vital:18194 , http://hdl.handle.net/10353/d1011183
- Description: Kantian Philosophy: PHL 223, supplementary examination February 2011.
- Full Text: false
- Date Issued: 2011-02