A life-history approach to the early ontogeny of the Mozambique tilapia Oreochromis mossambicus (Pisces, Cichlidae)
- Holden, Kathleen K, Bruton, Michael N
- Authors: Holden, Kathleen K , Bruton, Michael N
- Date: 1992
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447116 , vital:74585 , https://www.ajol.info/index.php/az/article/view/154193
- Description: The early ontogeny of Oreochromis mossambicus (Peters) was followed from the time of egg activation until the juvenile period. Development is direct and consists of an embryonic period of approximately 15 days. The embryonic period can be divided into a cleavage, an embryonic and a free-embryonic phase. A detailed developmental description is given and the relationship between the early ontogeny and the early life-history pattern is examined. The terminology used for the last step of the free-embryonic phase and a possible truncated larval period is discussed.
- Full Text:
- Date Issued: 1992
- Authors: Holden, Kathleen K , Bruton, Michael N
- Date: 1992
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447116 , vital:74585 , https://www.ajol.info/index.php/az/article/view/154193
- Description: The early ontogeny of Oreochromis mossambicus (Peters) was followed from the time of egg activation until the juvenile period. Development is direct and consists of an embryonic period of approximately 15 days. The embryonic period can be divided into a cleavage, an embryonic and a free-embryonic phase. A detailed developmental description is given and the relationship between the early ontogeny and the early life-history pattern is examined. The terminology used for the last step of the free-embryonic phase and a possible truncated larval period is discussed.
- Full Text:
- Date Issued: 1992
The distribution of the Wattled Starling in southern Africa
- Authors: Craig, Adrian J F K
- Date: 1992
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447896 , vital:74682 , https://doi.org/10.1080/00306525.1992.9634180
- Description: Dated distribution records of the Wattled Starling Creatophora cinerea have been assembled from the literature, museum specimens, atlas records, and other unpublished observations. The bulk of these records are from the period 1980–89. Breeding records are sparse, but breeding appears to be seasonal in the winter rainfall area. In summer rainfall areas nesting occurs from spring through to autumn, dependent on the presence of abundant insects. In most areas winter records (June to August) predominate, but in the eastern lowveld areas of South Africa Wattled Starlings are recorded most often in spring and summer. The species is correctly described as nomadic, and the pattern of occurrence does not suggest regular migration.
- Full Text:
- Date Issued: 1992
- Authors: Craig, Adrian J F K
- Date: 1992
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447896 , vital:74682 , https://doi.org/10.1080/00306525.1992.9634180
- Description: Dated distribution records of the Wattled Starling Creatophora cinerea have been assembled from the literature, museum specimens, atlas records, and other unpublished observations. The bulk of these records are from the period 1980–89. Breeding records are sparse, but breeding appears to be seasonal in the winter rainfall area. In summer rainfall areas nesting occurs from spring through to autumn, dependent on the presence of abundant insects. In most areas winter records (June to August) predominate, but in the eastern lowveld areas of South Africa Wattled Starlings are recorded most often in spring and summer. The species is correctly described as nomadic, and the pattern of occurrence does not suggest regular migration.
- Full Text:
- Date Issued: 1992
Turbidity-induced changes in feeding strategies of fish in estuaries
- Hecht, Thomas, Van der Lingen, C D
- Authors: Hecht, Thomas , Van der Lingen, C D
- Date: 1992
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/446960 , vital:74573 , https://hdl.handle.net/10520/AJA00445096_644
- Description: The aim of this study was to determine the effect of turbidity on the feeding strategies of fish in estuaries. Three species representing different feeding guilds were selected for the investigation. These were Elops machnata (representative piscivore), Pomadasys commefsonnii (a macrobenthivore) and Athefina breviceps (a planktivore). The stomach contents of these fish were examined from a clear and a turbid estuary and some experimental work was carried out on A. brevic8ps to test the hypothesis that turbidity affects feeding behaviour. Turbidity was found to have no effect on size selection of prey, but feeding rate, particularly of visual predators, was reduced at higher turbidity levels. This was caused by a decrease in the reactive distance of the fish. It would appear that in order to optimize the aquisition of food under different turbidity conditions fishes have the ability to change their feeding strategies. Visual predators are more affected by turbidity than are macrobenthic feeders.
- Full Text:
- Date Issued: 1992
- Authors: Hecht, Thomas , Van der Lingen, C D
- Date: 1992
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/446960 , vital:74573 , https://hdl.handle.net/10520/AJA00445096_644
- Description: The aim of this study was to determine the effect of turbidity on the feeding strategies of fish in estuaries. Three species representing different feeding guilds were selected for the investigation. These were Elops machnata (representative piscivore), Pomadasys commefsonnii (a macrobenthivore) and Athefina breviceps (a planktivore). The stomach contents of these fish were examined from a clear and a turbid estuary and some experimental work was carried out on A. brevic8ps to test the hypothesis that turbidity affects feeding behaviour. Turbidity was found to have no effect on size selection of prey, but feeding rate, particularly of visual predators, was reduced at higher turbidity levels. This was caused by a decrease in the reactive distance of the fish. It would appear that in order to optimize the aquisition of food under different turbidity conditions fishes have the ability to change their feeding strategies. Visual predators are more affected by turbidity than are macrobenthic feeders.
- Full Text:
- Date Issued: 1992
An approach to the evaluation of microcomputer operating systems with respect to real-time issues
- Authors: Wells, George C
- Date: 1991
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430484 , vital:72694 , https://doi.org/10.1016/0165-6074(91)90014-K
- Description: This paper gives an overview of the approach used for the assessment of several operating systems for microcomputers. The operating systems are all commercial products and cover a spectrum ranging from general purpose operating systems to small, real-time operating systems. The criteria used for the evaluation are discussed and the approach used is discussed in detail. The results of the evaluation are not discussed in this paper.
- Full Text:
- Date Issued: 1991
- Authors: Wells, George C
- Date: 1991
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430484 , vital:72694 , https://doi.org/10.1016/0165-6074(91)90014-K
- Description: This paper gives an overview of the approach used for the assessment of several operating systems for microcomputers. The operating systems are all commercial products and cover a spectrum ranging from general purpose operating systems to small, real-time operating systems. The criteria used for the evaluation are discussed and the approach used is discussed in detail. The results of the evaluation are not discussed in this paper.
- Full Text:
- Date Issued: 1991
The Behaviour Of Palewinged Starlings And A Comparison With Other Onychognathvs Species
- Craig, Adrian J F K, Hulley, Patrick E, Walter, Grenville H
- Authors: Craig, Adrian J F K , Hulley, Patrick E , Walter, Grenville H
- Date: 1991
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447868 , vital:74680 , https://doi.org/10.1080/00306525.1991.9639648
- Description: Pairs of Palewinged Starlings associate throughout the year and roost at the nest sites. Flock sizes are generally small, even during the non-breeding season. Allofeeding and allopreening have not been recorded. Wing displays emphasize the white region of the primaries. The territory appears to be restricted to the nest site. Interspecific aggression occurred between Redwinged and Palewinged Starlings, and was also directed at other Ed species frequenting the cliff. A form of ceremonial gathering occurs re in Palewinged Starlings. A review of the literature suggests that on behavioural grounds the Palewinged Starling shows no close affinity to the Redwinged Starfng or to any other member of the genus.
- Full Text:
- Date Issued: 1991
- Authors: Craig, Adrian J F K , Hulley, Patrick E , Walter, Grenville H
- Date: 1991
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447868 , vital:74680 , https://doi.org/10.1080/00306525.1991.9639648
- Description: Pairs of Palewinged Starlings associate throughout the year and roost at the nest sites. Flock sizes are generally small, even during the non-breeding season. Allofeeding and allopreening have not been recorded. Wing displays emphasize the white region of the primaries. The territory appears to be restricted to the nest site. Interspecific aggression occurred between Redwinged and Palewinged Starlings, and was also directed at other Ed species frequenting the cliff. A form of ceremonial gathering occurs re in Palewinged Starlings. A review of the literature suggests that on behavioural grounds the Palewinged Starling shows no close affinity to the Redwinged Starfng or to any other member of the genus.
- Full Text:
- Date Issued: 1991
A review of the biology of the Blackbellied Starling and other African forest starlings
- Authors: Craig, Adrian J F K
- Date: 1989
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447730 , vital:74670 , https://doi.org/10.1080/00306525.1989.9639610
- Description: The Blackbellied Starling Lamprotornis corruscus is the only true forest starling in southern Africa. At the southern end of its coastal range it is an irregular visitor, and it may move according to food availability. The limited data on breeding, moult and seasonal occurrence are discussed. Only two subspecies are recognised. A brief survey of the 12 African starlings of evergreen forests shows that little is known about their basic biology or their role as highly mobile frugivores.
- Full Text:
- Date Issued: 1989
- Authors: Craig, Adrian J F K
- Date: 1989
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447730 , vital:74670 , https://doi.org/10.1080/00306525.1989.9639610
- Description: The Blackbellied Starling Lamprotornis corruscus is the only true forest starling in southern Africa. At the southern end of its coastal range it is an irregular visitor, and it may move according to food availability. The limited data on breeding, moult and seasonal occurrence are discussed. Only two subspecies are recognised. A brief survey of the 12 African starlings of evergreen forests shows that little is known about their basic biology or their role as highly mobile frugivores.
- Full Text:
- Date Issued: 1989
Nesting of sympatric redwinged and pale winged starlings
- Craig, Adrian J F K, Hulley, Patrick E, Walter, Grenville H
- Authors: Craig, Adrian J F K , Hulley, Patrick E , Walter, Grenville H
- Date: 1989
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447827 , vital:74677 , https://doi.org/10.1080/00306525.1989.9634513
- Description: Observations were made over four breeding seasons at Cradock, South Africa, where Redwinged Starlings Onychognathus morio and Palewinged Starlings O. nabouroup nest on the same cliffs. Nests were not accessible, and the stage of breeding was determined by the behaviour of the birds. Both species reuse the same nest sites, and only the females incubate, but both sexes feed the young. The timing of breedingMaybe more variable in the Palewinged Starling. A review of the available data on nest site selection and nest construction shows apparent species-specific differences: Redwinged Starlings usually nest on ledges, often on buildings, and use mud in the nest base; Palewinged Starlings favour vertical crevices, and do not use mud.
- Full Text:
- Date Issued: 1989
- Authors: Craig, Adrian J F K , Hulley, Patrick E , Walter, Grenville H
- Date: 1989
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447827 , vital:74677 , https://doi.org/10.1080/00306525.1989.9634513
- Description: Observations were made over four breeding seasons at Cradock, South Africa, where Redwinged Starlings Onychognathus morio and Palewinged Starlings O. nabouroup nest on the same cliffs. Nests were not accessible, and the stage of breeding was determined by the behaviour of the birds. Both species reuse the same nest sites, and only the females incubate, but both sexes feed the young. The timing of breedingMaybe more variable in the Palewinged Starling. A review of the available data on nest site selection and nest construction shows apparent species-specific differences: Redwinged Starlings usually nest on ledges, often on buildings, and use mud in the nest base; Palewinged Starlings favour vertical crevices, and do not use mud.
- Full Text:
- Date Issued: 1989
The application of real-time design techniques to simulation
- Authors: Wells, George C
- Date: 1989
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430541 , vital:72698 , 10.1049/sej.1989.0040
- Description: The paper discusses the application of the Ward and Mellor structured development techniques for real-time systems to the field of simulation. The tools and heuristics used by Ward and Mellor are extended to provide a useful approach to the design of real-time simulations. This is illustrated by the example of a real-time simulation of a manufacturing plant and process control system.
- Full Text:
- Date Issued: 1989
- Authors: Wells, George C
- Date: 1989
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430541 , vital:72698 , 10.1049/sej.1989.0040
- Description: The paper discusses the application of the Ward and Mellor structured development techniques for real-time systems to the field of simulation. The tools and heuristics used by Ward and Mellor are extended to provide a useful approach to the design of real-time simulations. This is illustrated by the example of a real-time simulation of a manufacturing plant and process control system.
- Full Text:
- Date Issued: 1989
Co-operative breeding in the Pied Starling
- Authors: Craig, Adrian J F K
- Date: 1987
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447786 , vital:74674 , https://doi.org/10.1080/00306525.1987.9633905
- Description: Pairs of Pied Starlings Spreo bicolor build the nest, but only the female incubates. After the chicks hatch, subadult and juvenile birds help feed the young. Helpers also feed young after they leave the nest. In most cases parents contribute more than the helpers which may attend several different nests. Associations between members of the same breeding group may persist for up to three successive seasons.
- Full Text:
- Date Issued: 1987
- Authors: Craig, Adrian J F K
- Date: 1987
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447786 , vital:74674 , https://doi.org/10.1080/00306525.1987.9633905
- Description: Pairs of Pied Starlings Spreo bicolor build the nest, but only the female incubates. After the chicks hatch, subadult and juvenile birds help feed the young. Helpers also feed young after they leave the nest. In most cases parents contribute more than the helpers which may attend several different nests. Associations between members of the same breeding group may persist for up to three successive seasons.
- Full Text:
- Date Issued: 1987
Breeding condition of male red bishops under artificial photoperiods
- Authors: Craig, Adrian J F K
- Date: 1985
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447761 , vital:74672 , https://doi.org/10.1080/00306525.1985.9639572
- Description: Testis development, as indicated by bill colour changes, and moult were followed over two years in nine birds kept under constant conditions of 14 h light:10 h dark. All birds maintained at least partial nuptial dumage throughout this period, but most continued normal cycles of wing moult. The testes continued to show cycles of enlargement and regression.
- Full Text: false
- Date Issued: 1985
- Authors: Craig, Adrian J F K
- Date: 1985
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447761 , vital:74672 , https://doi.org/10.1080/00306525.1985.9639572
- Description: Testis development, as indicated by bill colour changes, and moult were followed over two years in nine birds kept under constant conditions of 14 h light:10 h dark. All birds maintained at least partial nuptial dumage throughout this period, but most continued normal cycles of wing moult. The testes continued to show cycles of enlargement and regression.
- Full Text: false
- Date Issued: 1985
The distribution of the Pied Starling, and southern African biogeography
- Authors: Craig, Adrian J F K
- Date: 1985
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447882 , vital:74681 , https://doi.org/10.1080/00306525.1985.9639580
- Description: The Pied Starling is restricted to South Africa, Lesotho and Swaziland, but within this region it occupies a variety of habitats. Its modern distribution is certainly influenced by its association with man. However, a comparison with other vertebrate species, and with patterns of plant distribution, suggests that its geographical distribution has been determined primarily by its evolutionary history. A hypothesis for the origin of this species leads to several predictions concerning biogeography in southern Africa.
- Full Text:
- Date Issued: 1985
- Authors: Craig, Adrian J F K
- Date: 1985
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447882 , vital:74681 , https://doi.org/10.1080/00306525.1985.9639580
- Description: The Pied Starling is restricted to South Africa, Lesotho and Swaziland, but within this region it occupies a variety of habitats. Its modern distribution is certainly influenced by its association with man. However, a comparison with other vertebrate species, and with patterns of plant distribution, suggests that its geographical distribution has been determined primarily by its evolutionary history. A hypothesis for the origin of this species leads to several predictions concerning biogeography in southern Africa.
- Full Text:
- Date Issued: 1985
The winter diet of gentoo penguins at Marion Island
- LaCock, G D, Hecht, Thomas, Klages, N
- Authors: LaCock, G D , Hecht, Thomas , Klages, N
- Date: 1984
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448453 , vital:74731 , https://doi.org/10.1080/00306525.1984.9634486
- Description: The diet of Gentoo Penguins Pygoscelis papua at Marion Island was studied during September 1982. Samples were obtained from 64 birds using a stomach-pump. Fish accounted for 70% of the diet by wet weight, and crustaceans 30%. Fishes occurred in 72% of the samples, crustaceans in 75%, cephalopods in 13%, and molluscs in 8%. Cephalopods and molluscs did not form a significant proportion of any single sample. Harpagifer georgianus was the predominant fish in the diet (92,7% of otoliths recovered), and Nauticaris marionis was the only crustacean.
- Full Text:
- Date Issued: 1984
- Authors: LaCock, G D , Hecht, Thomas , Klages, N
- Date: 1984
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/448453 , vital:74731 , https://doi.org/10.1080/00306525.1984.9634486
- Description: The diet of Gentoo Penguins Pygoscelis papua at Marion Island was studied during September 1982. Samples were obtained from 64 birds using a stomach-pump. Fish accounted for 70% of the diet by wet weight, and crustaceans 30%. Fishes occurred in 72% of the samples, crustaceans in 75%, cephalopods in 13%, and molluscs in 8%. Cephalopods and molluscs did not form a significant proportion of any single sample. Harpagifer georgianus was the predominant fish in the diet (92,7% of otoliths recovered), and Nauticaris marionis was the only crustacean.
- Full Text:
- Date Issued: 1984
Moult in southern African passerine birds: a review
- Authors: Craig, Adrian J F K
- Date: 1983
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447813 , vital:74676 , https://doi.org/10.1080/00306525.1983.9634475
- Description: In the most recent checklist 398 passerine species are recorded for southern Africa. This paper lists information on the moult of 114 species, of which 27 are Palaearctic migrants, or birds for which there are data from European populations only. For 65 additional species data of uncertain relevance to southern African populations are included in appendices. There is much interspecific variation in both pattern and timing, even between members of the same family and genus. Aspects requiring special attention in future studies are discussed.
- Full Text:
- Date Issued: 1983
- Authors: Craig, Adrian J F K
- Date: 1983
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447813 , vital:74676 , https://doi.org/10.1080/00306525.1983.9634475
- Description: In the most recent checklist 398 passerine species are recorded for southern Africa. This paper lists information on the moult of 114 species, of which 27 are Palaearctic migrants, or birds for which there are data from European populations only. For 65 additional species data of uncertain relevance to southern African populations are included in appendices. There is much interspecific variation in both pattern and timing, even between members of the same family and genus. Aspects requiring special attention in future studies are discussed.
- Full Text:
- Date Issued: 1983