Browsing by Subject "Ornithology"

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    Accessing silence : research methods into sexual harassment : a case study of the Committee of Enquiry into Sexual Harassment at the University of Cape Town
    (1994) Sutherland, Carla; Marv Simons and Pam Reynolds
    Biological extinction rates have escalated by as much as 1000 times the background extinction rate over the last 1500 years, causing concern over the long-term survival of many species. Avian extinctions since 1600 have been well documented relative to other taxa, as have current levels of avian threat. This study analyses avian extinctions post-1600 and current threats in an attempt to develop some predictive capacity about which avian taxa should be awa,rded the highest conservation priority. Analyses performed include examinations of the causes of avian extinction and threat, geographical location of extinct and threatened species, prehistoric and historical extinction rates, endemicity, migration, bird body size and phylogenetic diversity. An analysis dealing with historical and phylogenetic aspects of endangered and critically threatened species was performed, from which the world's most threatened species were identified. Factors which were the primary cause of historical extinctions are generally not the primary factors threatening today's extant avifauna. Whilst introduced predators and exploitation were primary causes of historical extinctions, habitat destruction poses the greatest threat to extant birds. Species predisposed to extinction typically have restricted ranges, and, compounded by habitat loss, these ranges are becoming more restricted. This has resulted in mainland-dwelling species becoming as prone to extinction as island-dwelling species have been historically. IIltroduced predators, however, do still threaten many of the world's most threatened species and their potential effects are highlighted in the phylogenetic analysis. Already, many extinctions may be inevitable over the next 25 years as a result of habitat loss. The magnitude of extinctions across all animal and plant species in the next few decades could be comparable with that of previous mass extinctions unless immediate conservation action is taken. However, future conservation efforts will have to be prioritized, and this study is intended as a contribution towards such a prioritization exercise.
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    African penguin (Spheniscus demersus) distribution during the non-breeding season : preparation for, and recovery from, a moulting fast
    (2016) Roberts, Jennifer; Ryan, Peter G; Pichegru, Lorien; Wanless, Ross M; Hagen, Christina
    Little is currently known about the spatial ecology of the endangered African penguin during the non-breeding season. As foraging success during this period is critical to adult survival, this project explores their dispersal patterns, as well as the degree of overlap with commercial purse-seine fisheries which target the same prey. African penguins from two colonies (Bird Island, Algoa Bay, south coast and Dassen Island, west coast) were tracked over 3 non-breeding seasons using Platform Terminal Transmitters and Global Positioning System devices to explore their pre- and post-moult dispersal patterns. Dispersal trips varied greatly between individuals, but there were still significant differences in the dispersal patterns found between islands and between life history-stages at Dassen Island. Bird Island penguins tended to make frequent, short trips, returning to their breeding colony in between, whereas Dassen Island penguins followed one of two strategies: either making few (up to 3) very long trips (up to 4000km), or adopting a central-place foraging pattern based at a point along the coast, distant from their breeding colony. At Dassen Island a clear spatial divide is evident with most pre-moulters dispersing south whereas most post-moult birds dispersed north, off the west coast. Bird Island penguins all moulted at their breeding colony and seldom visited either the adjacent coastline or other islands. During pre-moult, Dassen Island birds often spent nights close to shore along the coast or at other colonies and about a quarter of them moulted at another colony, most often at Stony Point, on the mainland east of Cape Point. Five dispersal patterns (defined in terms of the direction and distance of the furthest point reached) were identified for birds from Dassen Island and there is some indication that different dispersal patterns have distinct survival implications. Over 60% of PTT loss (a proxy for penguin mortality) occurred in a small area in the northern part of St Helena Bay, offshore from Lambert's Bay and Strandfontein and could be due to high levels of seal predation, which has been previously documented in the area. Commercial small pelagic fishing data were analysed over three years (2012-2014). Average fishing effort decreased each month from September to December (when hardly any fishing occurred in any of the three years) and there was much greater fishing effort along the west coast than on the south coast. Commercial fishing effort was compared to penguin track data to assess the degree of potential overlap between these two pelagic predators. Firstly, the spatial overlap between core penguin non-breeding dispersal areas and core fishing areas was assessed on a broad temporal scale (three years). Bird Island penguins were found to be more spatially removed from fishing activity with no overlap in core fishing and dispersal areas on the south coast. Compared to the size of their dispersal area, Dassen Island penguins which stayed along the lower west coast showed the highest overlap with core fishing areas. The two most common dispersal patterns exhibited by Dassen Island penguins both involve journeying to areas outside the range of purse-seine fishing, indicating the possibility of avoidance behaviour once the pressures of breeding are lifted. Direct (daily) overlap between commercial fishing effort and penguin tracks was studied although the low frequency of the penguin position data restricted the analysis to a 20 km scale. The results were similar to those described above, with most direct overlap occurring between Dassen Island and Gansbaai.
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    Are foraging patterns of aerial predators influencing diurnal activity of their prey?
    (2011) Retief, Kirsten; Simmons, Robert E
    There is often a reciprocal relationship between predators and their dominant prey. This results in continuous co-evolution, where the prey selects more efficient ways to avoid predation and the predator selects more efficient ways of catching prey. The aim of this study was to determine if aerial predators (raptors) influence diurnal activity patterns of their prey (mice). Sampling of both raptors and mice was done simultaneously during autumn, winter and spring at two different study sites in three different habitats on South Africa's arid west coast. Sixty PVC mouse traps were checked every half hour throughout all daylight hours and raptors were observed using scan sampling every two minutes. A total of 1228 rodents were trapped consisting mainly of the diurnal mouse, Rhabodmys pumilio and a total of 197 hours was spent observing hunting behaviour of four raptor species: Black and African Marsh Harriers (Circus maurus and C. ranivorus), Black-shouldered Kite (Elanus caeruleus) and Rock Kestrel (Falco rupicolus). All birds hunt rodents on a regular basis and all were beginning to breed towards the end of my study. Results showed significantly higher small mammal activity during winter and in habitats with dense vegetation. Diurnal small mammal activity peaks appeared to shift randomly between sites, habitats and seasons, thereby avoiding predation through unpredictability of activity. Small mammal activity patterns deliberately avoided peak foraging times of raptors during winter at the Pelican site; however this relationship was not linked to any climatic variables to explain how mice avoid high predation periods. Raptors selected peak foraging times dming periods of high small mammal activity at the Dune site during winter; however wind speed and cloud cover were correlated with both raptor foraging and small mammal activity, thereby influencing the relationship between the predator and the prey. In conclusion, no reoccurring diurnal peaks in small mammal activity were seen across the three seasons and this may have been an anti-predation strategy, because predators would find it more difficult to predict high prey activity. However the raptors it seemed were selecting periods of high mice activity at one site when weather conditions allowed.
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    Aspects of the behaviour and ecology of White-fronted Sandplovers and Sanderlings on a South African sandy beach
    (1986) Crowe, Anna Aletta; Siegfried, Roy
    The dissertation comprises a general introduction, five chapters and a summary-synthesis which is designed to link the chapters into a cohesive account. Chapter 1 deals with the avian population of a southwestern Cape sandy shore and compares this population with those of sandy beaches in the eastern Cape and Natal. The abundance of birds and the estimated energy requirements of the avian populations in these three geographical areas increase during the austral summer, due to an influx of migrants from the northern hemisphere. The proportion of migrants to residents varies geographically, being greater in the southwestern Cape and Natal than in the eastern Cape. Chapter 2 summarizes information on the systematics, global distribution and morphology of two small shorebirds, the White-fronted Sandplover Charadrius marginatus and the Sanderling Calidris alba, which are identified in Chapter l as being dominant components of the southwestern Cape sandy shore avian population. Chapter 3 reports on the spatial and temporal use of the intertidal habitat by foraging White-fronted Sandplovers ·and Sanderlings. Interactions between these two species are discussed in the light of competition theory. The foraging ecology of the Sanderling and White-fronted Sandplover at Ouskip differed strikingly. Although both species exhibited a tidal cycle in foraging activities, rather than a diurnal cycle, White-fronted Sandplovers tended to feed during the latter half (i.e. mid to high tide), whereas Sanderlings fed during the first half (i.e. low to mid tide) of the tidal cycle. Both species' foraging activity also varied spatially and seasonally. White-fronted Sandplovers fed primarily in drier microhabitats above high tide level, and Sanderlings in wetter microhabitats near the water's edge. In Chapter 4, the size and structure of Sanderling flocks are described. The frequency distribution of flock sizes of wintering Sanderlings foraging on the sandy beach at Ouskip was bimodal, with a peak at small flock sizes and another at large flock sizes. It is hypothesized that large groups of Sanderlings consist of individuals searching for subterranean prey, and that small groups consist of subsets of these larger groups which have located food patches. Chapter 5 is an analysis of breeding periodicity in White-fronted Sandplovers in southern Africa, and focuses on the relationships between geographical and year-toyear variation in breeding activity and rainfall patterns, food availability and the possible effects of competition with migrant shorebirds. This species exhibits significant geographical variation in breeding season, and significant year-to-year variation within an area which has winter (May - August) rainfall. There was no year-to-year variation in breeding season within an area with summer (November - February) rainfall.
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    Aspects of the ecology of migrant shorebirds (Aves: Charadrii) at the Berg River estuary, South Africa
    (1992) Kalejta, Bozena; Hockey, Phil A R
    The waterbird populations of the Berg River estuary, South Africa, were studied from September 1987 to April 1989. The main objectives of the study were to assess the importance of the estuary for Palearctic-breeding migratory waders and to identify the factors affecting their distribution, abundance and behavioural patterns. The findings were related to the dispersion patterns of waders on the east Atlantic seaboard, and their significance was evaluated in the light of predictions of current models for the migratory behaviour of shorebirds. Controversy over the Winter competition model is discussed. The intertidal mudflats (144 ha) at the Berg River estuary support an exceptionally high density of migratory shorebirds during the austral summer. The high density of birds results in a high predation pressure. Although the rate of prey removal by birds is one of the highest recorded in the east Atlantic, it represents only 17% of the annual production of invertebrates. A bird-exclusion experiment confirmed that birds have little impact on their prey populations. Although the energy balance for the majority of species was apparently negative for much of the austral summer, the energy deficits measured in the field were less than those recorded in north temperate estuaries. The highest predation pressure by birds coincided with the period of highest production of the most important invertebrate prey. Because of low prey diversity in the estuary, there was considerable overlap in the prey species taken by different bird species. The preferred prey of most species were nereid worms. Within this prey class there were clear differences in the size classes of worms eaten by different birds. The distribution of birds on the estuary was related to both biotic and abiotic factors. The observed patterns of partitioning of both food and space resources was attributed to the superabundance of prey and to interspecific differences in foraging techniques unrelated to competition. The spatial redistribution of birds within the estuary during the first four months after their arrival from the breeding grounds was related to changes in feeding conditions on their preferred foraging sites, rather than density-dependent factors mediated by competition. I propose that a combination of high prey abundance and production, coupled with an apparently low level of competition, makes the Berg River an attractive nonbreeding site for migrant waders. Their relatively sound energy budgets and the benign climate may enhance nonbreeding survivorship sufficiently to offset any additional risks incurred in long-distance migration.
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    Aspects of the foraging and breeding ecology of the Southern African Kestrel, Falco tinnunculus rupicolus
    (1993) Van Zyl, Anthony John; Siegfried, Roy
    A study of the ecology of the Southern African Kestrel was made in two areas of differing topography in the Eastern Cape Province (32 °S) of South Africa. The main objectives of the study were to describe foraging parameters (behaviour-time budgets, hunting success and diet) and breeding parameters (clutch size, hatching and fledging success, nestling, fledging and post-fledging periods) of the Southern African Kestrel. These parameters were compared to those from studies made on the European Kestrel (Falco tinnunculus tinnunculus) in western Europe (53 °N) in an environment which fluctuates relatively more than the South African study sites. Predictions concerning foraging and breeding ecology made by life-history theory in stable and fluctuating environments prompted the erection of the following hypotheses which were examined in this study. 1. Common Kestrels (Falco tinnunculus) in relatively stable environments have a more consistent but lower foraging yield than those breeding in fluctuating environments. 2. Common Kestrels in relatively stable environments have lower reproductive rates (longer incubation, nestling and post-fledgling dependence periods, later age at first breeding and longer life-span) than those in fluctuating environments. Southern African Kestrels spent different proportions of time of the two main hunting methods used, perch- and hover-hunting, than the European Kestrel. Perch-hunting was the predominant hunting method used by the Southern African Kestrel compared to hover-hunting in the European Kestrel. Southern African Kestrels had a higher prey-capture success for both hunting techniques. However, daily food intake was lower in Southern African Kestrels because a high proportion of the diet consisted of small invertebrates. Average clutch size was smaller in the Southern African Kestrel than that of the European Kestrel and Southern African Kestrels fledged on average fewer young. However, incubation, nestling and post-fledging periods were within the range recorded for the European Kestrel. The hypothesis that Common Kestrels in relatively stable environments have lower foraging yields is supported by this study. Although results from this study suggest that food yields are more consistent in stable environments, it was unable to evaluate this adequately. The hypothesis that reproductive rates are lower in relatively stable environments is partly supported in this study, but more data are required for parameters such as incubation and nestling periods to confirm such trends.
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    Assessing the anthropogenic threats to vultures in the communal farmlands of Namibia
    (2017) Craig, Christie; Thomson, Robert; Santangeli, Andrea
    The use of poison by farmers to control livestock predators is a major threat to vulture populations across Africa. In Namibia, there is now some understanding of poison use on commercial farms, but the situation in the communal farmlands is still poorly understood. Using a series of 36 questions, I interviewed 367 communal farmers to assess the prevalence of poison use across the north-west, north and eastern communal land. I found that 18% (SE 2.8) of farmers had killed a predator in the last year and 1.7% (SE 2.1) used poison to do so. I mapped the probability of poison use across the communal regions surveyed and found that poison use is predicted to be higher (up to 7% of farmers using poison) in some areas of the upper north-west. In contrast to previous research, those living adjacent to protected areas did not experience greater losses to predators and as a result were not more inclined to use poison. I found that those using poison are more likely to own greater numbers of livestock, particularly large livestock. Overall, my study suggests that poison use is approximately 12 times lower in the communal areas than on commercial farms. A number of farmers expressed that it is dangerous to use poison on communal land as the risk of non-target impacts is much higher where the land is not fenced and is communally used. Nonetheless there are communal farmers who are using poison and this poses a risk to already threatened vulture populations. Lastly, I did a survey to look at the farmers' local knowledge about vultures, their attitudes towards them and any cultural value that vultures hold. Overall vultures were viewed positively by farmers. The cultural use of vulture parts appeared fairly uncommon, with 9.5% of farmers reporting that they knew of uses. Many farmers indicated that the cultural use of vulture parts was something practiced by previous generations. Feathers were the most commonly used part, mainly for decorations and making arrows. From my assessment, it appears that anthropogenic threats to vultures in communal areas are fairly low. The cultural use of vulture body parts is rare. In addition, poison is used but this practice is not nearly as common as it is on commercial farms. Since poison can have such devastating impacts on vulture populations, I nonetheless advise that reactive and preventative measures are put in place to reduce poisoning and minimise the impact when poison is used. The identified 'hotspots' of poison use will assist local authorities to focus their poison mitigation efforts.
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    Behavioural ecology of lesser sheathbills Chionis minor at Marion Island
    (1980) Burger, Alan Eckard; Siegfried, W R
    Adaptations to island life have seldom been studied in birds outside temperate or tropical regions. Lesser Sheathbills Chionis minor (Charadriiformes; Chionididae) were studied at Marion Island (46°54'S, 37°45'E) and the ways in which their feeding ecology, breeding biology and social behaviour were adapted to existence on a sub-Antarctic island were assessed. The birds' reproductive output and post-fledging survival rates were estimated and probable factors limiting the population examined. Seasonal and spatial variations in the diet and foraging habits were related to the quality, availability and distribution of food, and the effects of interspecific competition, the weather and predators. The adaptiveness of the broad trophic niche was investigated. A hypothesis that the variable social behaviour facilitated exploitation of variable food resources to benefit individual birds was examined; particular attention was paid to territoriality among breeding (summer) and non-breeding (winter) adults within penguin colonies and flocking amongst birds foraging on the coastal plain. Time and energy budgets of birds feeding in these habitats were drawn up. Displays by Lesser Sheathbills were described and their functions in territories, flocks, at nest sites and in sexual interactions were quantitatively assessed.
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    Behavioural ecology of Peregrine and Lanner falcons in South Africa
    (1998) Jenkins, Andrew Robert; Hockey, Phil A R
    The Peregrine Falcon Falco peregrinus is a specialized predator of birds. It occurs almost worldwide but is generally uncommon. In many areas, it is sympatric with one of a complex of similar, less specialized, congeneric species (subgenus Hierofalco, the desert falcons). Peregrine density and productivity tend to decrease with latitude, while desert falcons may be most successful in the tropics. This study compares the biology of Peregrines and sympatric Lanner Falcons F. biarmicus in South Africa, and examines the relative influence of resource limitation and interspecific competition with congeners on the natural regulation of Peregrine populations in tropical environments.
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    Biogeography and conservation of terrestrial afrotropical birds
    (1999) De Klerk, Helen Margaret; Crowe, Timothy M
    This study aimed to describe patterns of distribution in terrestrial Afrotropical birds, to investigate the causes of these patterns, and examine how aspects of distributional patterns may be used to prioritize local regions for conservation attention. Presence-only data were gathered and digitized at one-degree square scale for 1686 terrestrial bird species that breed on or regularly visit sub-Saharan Africa as non-breeding migrants. Biogeographical analysis of the 1437 species that are globally restricted to sub-Saharan Africa (Afrotropical endemics) revealed a suite of geographical areas that have a homogenous and characteristic avifaunal composition, termed avifaunal zones. The approach used in this study ensured representativeness in the resultant biogeographical classification scheme, which was not biased towards avifaunas that are species rich or that contain many narrow endemics, and further included avifaunas that consisted of few, but taxonomically and ecologically distinct species (e.g. the Namib Province). Analysis of zonal boundaries exhibiting high levels of turnover, defined specifically as species replacement, were distinguished from zonal boundaries that are characterised by species richness gradients. For instance, the northern forest-savanna boundary between the Guineo-Congolian and Northern Savanna Subregions was shown to consist of a sharp ecotone between forest and savanna, whereas the boundary between the Northern Savanna and Northern Arid Subregions was shown to be dominated by species drop-outs. This shows that whereas the Northern Savanna Subregion represents a unique avifauna that is distinct from that of the Guineo-Congolian Subregion, the Northern Arid Subregion is merely a depauparate subset of the Northern Savanna avifauna. Patterns of species richness and narrow endemism where shown to differ between species groups that exhibit different life history characteristics (e.g. residents vs. migrants) and distributional characteristics Atrotropical endemics vs. nonendemics). Differences can probably be attributed to island biogeography and aerography theory.
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    Biogeography and ecology of African waterbirds
    (1986) Guillet, Alfredo; Crowe, Timothy M
    Patterns of distribution and diversity for African waterbirds are investigated at the continental, sub-continental, ecosystem and species levels. The focal species is the Great White Pelican Pelecanus onocrotalus, one of South Africa's 'Red Data' bird species. The 'focal' ecosystem is Rondevlei Bird Sanctuary (34°'04'S, 18°30'E), one of the few conserved areas in Africa set aside especially for waterbirds. Biogeographically, waterbirds partition Africa much more coarsely (into 8 vs 18 avifaunal zones) than do non-aquatic birds. Waterbird species diversity (number of species) and endemism are higher outside the tropics, and exhibit longitudinal gradients, with higher diversity in the east. Non-aquatic bird diversity is higher in the tropics and varies latitudinally. Spatia-temporal variation in habitat availability and quality are the primary factors which control waterbird distribution, and the dynamic nature of waterbird dispersion is an adaptation to dramatically fluctuating habitats. About 69% o£ the variance in African waterbird species diversity can be explained in terms of present-day environmental variation. Part of the unexplained variance is attributed to the effects of historical factors, with areas of unexpectedly high species possibly acting as refugia during dry climatic phases.
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    Birds along a transect across KwaZulu-Natal: altitudinal preference and altitudinal migration
    (2018) Scott, Tanya; Underhill, Leslie G
    The special ornithological advantage of KwaZulu-Natal is the massive altitudinal gradient between the coastline and the Drakensberg Mountains, an altitudinal range in excess of 3000 m. It is one of the best places in the world to study altitudinal bird migration. This dissertation uses the bird data from the Second Southern African Bird Atlas Project (SABAP2), and altitudinal data from a Digital Elevation Model to try to understand altitudinal migration in a band of KwaZulu-Natal between 29°S and 30°S. The bird atlas provides data on a five minute grid, grid cells with sides of c. 9km, known as pentads. The Digital Elevation Model gives spot heights at 0.5 minute intervals. It therefore provides 100 altitudes in each pentad. There is a description of the data analysis approach used to relate bird species abundance to altitude and selected examples to show how the method works, illustrating the strengths and weakness of the approach. The developed method is then applied to the study area to investigate altitudinal migration. For each of the 304 species which occur with some regularity in the study area, the altitudinal height preferences in summer and winter are plotted and compared. Some species, such as African Dusky Flycatcher, are definite altitudinal migrants, and some species are definite residents having essentially identical altitudinal distributions in summer and winter, such as Black-bellied Starling. There are also many intermediate strategies. Numerous species have been proposed as altitudinal migrants in KwaZulu-Natal. These claims are evaluated against the results obtains in this dissertation. For some species, the suggestion that they are altitudinal migrants is clearly incorrect, and for other species the hypotheses are confirmed by the bird atlas data. The project attempted to determine if there were common factors that helped explain which species engaged in altitudinal migration. A set of life history characteristics for each species, including aspects such as diet, mass, habitat, etc, was used to evaluate if there was a relationship between the extent of altitudinal migration and these explanatory variables. No meaningful relationships were found. Explanations of altitudinal migrations therefore remain an enigma.
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    Breeding and dispersal implications for the conservation of the Southern Ground Hornbill Bucorvus leadbeateri
    (2017) Carstens, Kate; Ryan, Peter G; Little, Rob M; Thomson, Robert
    Populations of secondary tree-cavity nesting bird species are often limited by a shortage of natural nesting sites. For the Southern Ground Hornbill Bucorvus leadbeateri that typically nests in natural tree cavities, the shortage of nesting sites is one factor potentially limiting population growth. The species is listed as endangered in South Africa, and vulnerable throughout the rest of its range. Nest boxes can improve the conservation status of threatened birds that are limited by nest-site availability. However, nest boxes or other types of artificial nests are not always beneficial to the target species, and their value as a conservation tool needs to be tested for each species. Wooden nest boxes were installed for ground hornbills in a study area in north eastern South Africa with a paucity of natural nest sites. In this thesis, I assess productivity, timing of breeding, and dispersal in the Southern Ground Hornbill in a study area supplemented with nest boxes and discuss the implications for the conservation of this endangered species. Nest boxes are an effective conservation tool to improve productivity in areas lacking natural tree cavity nesting sites. Breeding success (calculated as the proportion of nesting attempts that fledged a chick) and predation levels were similar for groups using nest boxes and natural nests. Natural nests were more buffered against cooling night temperatures, but otherwise nest boxes provided nesting conditions that were no better than natural nests. Timing of breeding for nests in natural tree cavities and nest boxes were similar. However, groups with access to a nest box attempted breeding more often than groups with access to a natural nest only, resulting in an 15 % increase in the number of fledglings per group compared to an adjacent protected area with no artificial nests. The number of breeding groups in the study area increased by 460 % over 12 years. However, there is a limit to the density of breeding groups. Breeding success was highest when breeding density was one breeding group per 90-120 km², so nests should be spaced ~10 km apart. Given that the threats to ground hornbills include persecution and poisoning, increasing the reproductive rate by providing nest boxes should assist in slowing the decline by the increased recruitment of offspring into the population. Timing of breeding varied across years. The first eggs laid each year ranged from 9 September to 14 November, and median lay date was 03 November. Breeding attempts that were initiated early in the season were more likely to fledge a chick than those initiated later in the season. Timing of breeding was delayed during warmer springs, particularly under dry conditions. In savannas, hotter spring temperatures could limit food availability, for example, if higher temperatures cause the vegetation to dry out, resulting in a rapid decline in insect flush, especially in the phytophagous insect groups that form a large part of the ground hornbill diet. Factors to consider when constructing and placing nest boxes include thickness of the cavity walls, entrance height above ground and density of nest boxes placed in the landscape. Breeding attempts in natural nests and nest boxes with thicker nest walls and those positioned with higher entrances above the ground increased breeding success. Therefore, nests should be constructed with cavity walls at least 6 cm thick and placed so that the entrances are situated > 6 m above the ground. With 186 ringed chicks fledging from the study area after the installation of nest boxes, it was possible to observe their dispersal within the study area and farther away into the adjacent Kruger National Park. There was no evidence for sex-biased dispersal. Males and females dispersed at similar ages, and over similar distances, raising interesting questions about inbreeding avoidance mechanisms in this species. If females do not disperse beyond the range of related males, how do related individuals avoid pairing, and what forms of individual recognition exist?
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    Breeding behaviour and polygyny in the Red Bishop bird Euplectes orix (L.)
    (1973) Craig, Adrian John Fergus Knott; Broekhuysen, G J
    The red bishop bird, Euplectes orix, is a widespread and locally abundant member of the weaver family, the Ploceidae. It is found over most of Southern Africa, and as, far north as Uganda in the Eastern savannah belt. Large flocks may be found in association with other seedeaters, and the breeding colonies in reeds or tall grass in marshy areas may contain from five to several thousand birds. Recently it has also been recorded as nesting in standing crops in some areas. The adult birds are sparrow-sized, 12-15 cm in length and weighing 20-30 gm. The wing-length in the males ranges from 70-83 mm, and in females from 64-72 mm. Mackworth- Praed and Grant (1962) mention that birds from the Cape are larger, and that there appears to be a decrease in size of birds further north; measurements taken in this study seem to confirm this. During most of the year, both sexes are a mottled light brown colour, with a pale streak above the eye, and the underside pale to almost white, with darker streaks. However, at the beginning of the breeding season the adult males moult into their striking nuptial plumage: the abdomen and face mask are black, while the crown, throat, breast, rump, upper and under tail coverts are scarlet. The mantle feathers are tawny, but the wings and tail remain brown. The bill colour also changes from flesh-coloured to black. Hall and Moreau (1970), whose nomenclature is used for all the passerine species mentioned, regard three species Euplectes orix, franciscus and nigroventris as comprising the "orix superspecies". All three retain the brown wings and tail in the male breeding dress, but show variations in the extent of the red and black plumage. There is no apparent overlap in their ranges, or any evidence of inter-breeding. Two further species, E. hordeceu and E. gierowii, differ in that the wings and tail of the male are also black during the breeding season. Although slightly larger, their plumage is in other respects very similar, and these five species are termed a "species group". There is surprisingly little published information on any of these species. Lack (1935) first described territorial behaviour and polygyny in Euplectes hordeaceus, and later Moreau and Moreau (1938) and Fuggles-Couchman (1942) compared the ecology of E. hordeaceus and E. nigroventris. Skead (1956) produced a valuable basic study of E. orix, and showed it to be polygynous. Emlen (1957) made observations on several Euplectes species in Rhodesia, but the species orix and hordeaceus are confused in his paper, and it is not always clear which he is referring to. Later studies dealing with E. orix by Brooke (1964), Schmidt (1968) and Woodall (1971) are primarily concerned with clutch size, breeding seasons and nesting success, rather than behaviour. However, Crook (1962, 1963, 1964) has produced an important series of papers comprising a comparative study of behaviour in the entire weaver family. He refers mostly to the genus Euplectes, but also quotes observations on individual species, including E. orix. Collias and Collias (1964) have described nest-building behaviour in the weavers, but also mainly at the generic level.
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    Breeding Jackass Penguins as pelagic predators
    (1986) Wilson, Rory Paul; Siegfried, Roy
    The foraging of breeding Jackass Penguins Spheniscus demersus was studied in and around southwestern Cape Province, Saldanha Bay (33⁰ S, 18⁰ E), South Africa. Penguins are difficult to observe at sea. Hence, I devised a number of new techniques for studying the foraging behaviour of Jackass Penguins at sea. I built electronic and autoradiographic remote-sensing devices to measure swimming speed, distance travelled and time spent at each depth by foraging Jackass Penguins. Penguin swimming speed was reduced in proportion to the cross-sectional area of the devices, and results derived from birds wearing the devices had to be interpreted accordingly. Penguins do not regurgitate their stomach contents when handled, so I constructed a wet-offloading stomach pump which extracted 100% of the stomach contents. Using this pump, I determined that the rate of digestion of fish and squid by Jackass Penguins differed. Care is needed in diet interpretations where both fish and squid are major food items.
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    Can sociality buffer the impacts of climate change on a cooperatively-breeding bird, the southern pied babbler Turdoides bicolor?
    (University of Cape Town, 2020) Bourne, Amanda R; Cunningham, Susan J; Ridley, Amanda R; Spottiswoode, Claire
    Increasingly harsh and unpredictable climate regimes are affecting animal populations everywhere and understanding how species respond to current environmental variability is important for predicting vulnerability to climate change over longer timescales. Species living in characteristically harsh and unpredictable arid and semi-arid ecosystems are useful models for studying impacts of climate variability and change because these ecosystems are experiencing rapid increases in both average and maximum temperatures, as well as increased interannual rainfall variation, as a result of anthropogenic climate change. That animals living in highly variable environments are disproportionately more likely to engage in cooperative breeding implies that this strategy may buffer individuals against the negative effects of adverse climate conditions. An aspect of species' vulnerability to climate change that remains relatively unexplored is whether responses to environmental stressors might therefore be mitigated by sociality, particularly in those species in which group members are highly cooperative. In this thesis, I use behaviour, morphology, and physiology data that I collected over three consecutive austral summer field seasons (2016-2019) and A. Prof. Amanda Ridley's 15-year life history dataset (2003-2019, to which I contributed the last three years of data) for a cooperatively-breeding bird, the southern pied babbler Turdoides bicolor. I investigate the impacts of temperature, rainfall, and group size on interannual survival, behaviour, physiology, growth, and reproduction in southern pied babblers, taking a multidisciplinary approach combining behavioural ecology, life history, and ecophysiology. In order to avoid disturbance to the study population, I validated and implemented a non-invasive method for collecting physiological measurements (daily energy expenditure and water turnover). I also tested for the influence of interactions between weather and group size variables because the presence of significant interactions would provide evidence in support of a moderating effect of sociality. I found that exposure to high temperatures significantly constrained successful breeding and the interannual survival of both breeding adults and juvenile birds, and explored the mechanisms behind these observed relationships: adjustments in parental care behaviour, body mass loss, reduced nestling growth rates, and the physiological costs of care at high temperatures. Higher rainfall and larger groups sizes were generally associated with higher reproductive success and survival, but I found no evidence for an interaction between weather variables and group size: individuals across all group sizes experienced similar effects of conditions. I therefore conclude that 1) pied babblers will increasingly face challenges for population recovery and persistence in the near future as survival and reproduction are increasingly compromised by ever higher temperatures, and 2) a life history strategy that relies on the presence of helpers for successful breeding is unlikely to buffer individual group members against climatic variability and climate change in this cooperatively breeding species.
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    The causes of avian extinction and rarity
    (1997) Lennard, Christopher James; Hockey, Phil A R
    Biological extinction rates have escalated by as much as 1000 times the background extinction rate over the last 1500 years, causing concern over the long-term survival of many species. Avian extinctions since 1600 have been well documented relative to other taxa, as have current levels of avian threat. This study analyses avian extinctions post-1600 and current threats in an attempt to develop some predictive capacity about which avian taxa should be awarded the highest conservation priority. Analyses performed include examinations of the causes of avian extinction and threat, geographical location of extinct and threatened species, prehistoric and historical extinction rates, endemicity, migration, bird body size and phylogenetic diversity. An analysis dealing with historical and phylogenetic aspects of endangered and critically threatened species was performed, from which the world's most threatened species were identified. Factors which were the primary cause of historical extinctions are generally not the primary factors threatening today's extant avifauna. Whilst introduced predators and exploitation were primary causes of historical extinctions, habitat destruction poses the greatest threat to extant birds. Species predisposed to extinction typically have restricted ranges, and, compounded by habitat loss, these ranges are becoming more restricted. This has resulted in mainland-dwelling species becoming as prone to extinction as island-dwelling species have been historically. Introduced predators, however, do still threaten many of the world's most threatened species and their potential effects are highlighted in the phylogenetic analysis. Already, many extinctions may be inevitable over the next 25 years as a result of habitat loss. The magnitude of extinctions across all animal and plant species in the next few decades could be comparable with that of previous mass extinctions unless immediate conservation action is taken. However, future conservation efforts will have to be prioritized, and this study is intended as a contribution towards such a prioritization exercise.
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    Co-existence in the Phoebetria albatrosses at Marion Island
    (1977) Berruti, Aldo; Siegfried, W R
    The aims of the present study are threefold. Firstly, the coexistence of the two closely related, normally allopatric, albatross species is investigated in their zone of overlap where interspecific competition for food resources and nesting space is likely to be most acute. Secondly, the genetic isolation of the two species is investigated, as co-existence implies increased interspecific social interaction with associated increased possibilities of hybridization. Thirdly, the two species' possible evolutionary histories are examined in relation to their ecologies. Logistical constraints prevented study of fusca and palpebrata on the feeding grounds, i.e. at sea, and feeding could be studied only indirectly.
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    Comparative foraging ecology of macaroni and rockhopper penguins at the Prince Edward Islands
    (2017) Whitehead, Thomas Otto; Ryan, Peter G
    Penguins are one of the largest consumers of marine resources in the Southern Ocean and spend most of their lives at sea. Although the last four decades have seen technological advancements that have considerably expanded our knowledge about their at-sea behaviour, there is still much to be learned. Given the rapid ongoing ecosystem changes in the Southern Ocean, it is vital to better understand, firstly, how penguins respond to environmental variability, and secondly, how such changes alter ecological relationships between sympatric species. Being flightless, travel is slower and more costly for penguins than flying seabirds. This constrains their ability to find resources, particularly during the breeding season when they must regularly return to the colony to provision offspring. As penguins are colonial nesters, high foraging pressure near the colony can limit available resources, enhancing potential intra- and interspecific competition. At many localities, ecologically similar penguin species breed sympatrically. In such cases, co-existence is only thought possible through ecological segregation in space, time and/or diet. At the Prince Edward Islands, approximately 302,000 pairs of macaroni Eudyptes chrysolophus and 80,000 pairs eastern rockhopper E. chrysocome filholi penguins breed sympatrically. These populations are closer to parity than at any other locations where two eudyptid species breed sympatrically. Populations of both species at the Prince Edward Islands have declined in the last two decades, but drivers of these declines are poorly understood. The primary aim of this thesis was to better understand the foraging strategies of macaroni and rockhopper penguins at the islands and identify aspects of their ecology that allow them to co-exist. The secondary focus was to investigate how each species responds to environmental variability and assess how ecological interactions between species might be altered in an era of rapid global change. To study the at-sea habitat use and diving behaviour of penguins during chick-rearing and pre-moult periods, I used GPS loggers and time-depth recorders. To track penguins during the winter I used geolocation loggers and satellite transmitters. Stable isotope analyses were used to investigate trophic ecology during late winter, summer and pre-moult periods. During the breeding season, both species primarily foraged in pelagic waters beyond the shelf break (> 3000 m), with macaroni penguins foraging slightly farther offshore on average. However, rockhopper penguins breeding adjacent to the inter-island shelf foraged in shallow waters (< 200 m) over the shelf. Both species dived to similar depths (40 to 60 m), but macaroni penguins dived deeper more often. The diet of both species was dominated by two krill species (Thysanoessa vicina and Euphausia vallentini). Diving behaviour varied between years, with both species diving deeper when the SAF was located farther away and geostrophic flow was reduced. During these conditions, macaroni penguins fed on a larger proportion of myctophids whereas rockhopper penguins resorted to less energy-dense nototheniids. This highlights contrasting responses to periods of low krill availability. During the pre-moult period, habitat preferences were similar between species, with penguins travelling up to 1000 km south to forage in Antarctic Zone waters (SST 3-4 °C). However, a three-week difference in departure dates minimised spatiotemporal overlap between species. Diving behaviour was similar between species, but macaroni penguins performed more deep dives and encountered thermoclines more often. Stable isotope analyses revealed that macaroni penguins fed on a greater proportion of fish than rockhopper penguins, and revealed species-specific spatial responses to changes in primary productivity, with macaroni penguins travelling farther south in less productive years. During the 6-month long winter sojourn, macaroni penguins generally foraged in cooler waters (SST ~ 3 °C) compared to rockhopper penguins (5-6 °C). However, stable isotope analyses revealed that trophic and spatial overlap were high during late winter. Both species associated with mesoscale eddies and submesoscale filaments, suggesting that these features play an important role in aggregating prey during the resource-limited winter months. In summary, it appears that subtle differences exist to minimise competitive overlap between macaroni and rockhopper penguins. The three-week difference in the onset of breeding is integral to minimising competitive overlap during late winter, brood-guard/crèche, pre-moult and immediately following the moult. This allochrony staggers the peak energy demands of rockhopper penguins to reduce overlap with macaroni penguins. The larger-bodied macaroni penguins are capable of diving deeper, for longer and more efficiently than rockhopper penguins, which increases their behavioural flexibility and fitness by minimising stresses associated with reduced krill availability. Such differences in diving behaviour may explain contrasting population trends at the islands and suggests that rockhopper penguins may continue to decline at a faster rate than macaroni penguins if ongoing climate change continues to reduce prey availability around the Prince Edward Islands.
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    A conservation genetic study of threatened, endemic southern African seabirds
    (2014) Nupen, Lisa Jane; Bishop, Jacqueline M; Ryan, Peter G
    Molecular techniques have a broad, and growing, application in the field of wildlife conservation, ranging from the systematic identification and classification of taxa, through studying genetic connectivity between populations, to parentage and individual barcoding. While they are applied to a wide range of spatial- and temporal-scales, molecular approaches complement traditional methods used to classify, investigate and understand the natural world. This study uses multiple lines of evidence, at various scales, to investigate how seabird biology influences population-level responses to changing environments. The focal area is the Agulhas-Benguela Ecosystem (ABE) along the south-western coast of Africa. Globally, biodiversity loss due to environmental change in marine ecosystems is significantly affecting the phenology, distribution, dispersal patterns, and demographic rates of organisms across trophic-levels. Broad-scale changes are occurring that have consequences for both commercial fisheries and threatened marine top-predators. Seabirds are valuable indicators of the state of marine ecosystems, and changes in their distribution and dispersal patterns may reflect those of species in lower trophic-levels. This is the case in the ABE, where some endemic seabird species are better at responding to changes in their environment than others. Twentieth century shifts in the distribution of key pelagic prey species in the ABE have had serious consequences for endemic seabirds. The African Penguin Spheniscus demersus, Cape _ Gannet Moms capensis and Cape Cormorant Phalacrocorax capensis rely on these pelagic fish, and all three species are threatened and in decline. In this study population genetic and phylogeographic methods are used to: (i) quantify levels of genetic diversity, and determine regional-scale structure within all three focal species; (ii) explore fine-scale population structure in African Penguin; and (iii) compare wild and captive populations of African Penguins. The conservation of genetic diversity is essential for the long-term persistence of species. Population genetics can help us to understand the evolutionary processes that have shaped patterns of genetic diversity in the focal species, and predict how they might respond to further environmental changes. Comparative phylogeography, combined with capture-mark- recapture models based on ringing data and annual census counts, provide the most complete picture of the micro-evolutionary forces at play in this unique ecosystem, and highlight seabird life-history characteristics may facilitate adaptation and survival under novel conditions. This is the first conservation genetic study of endemic seabirds in the ABE. Although the three focal species differ in a number of aspects of their breeding and foraging ecology, and in some life-history characteristics, they have evolved under similar selective pressures across their shared range, and represent natural replicates that allow us to determine the dominant drivers of population genetic change. Flexibility in foraging behaviour and the degree of breeding site fidelity exhibited by each of the three focal species affect the rate and effectiveness of their demographic responses to changes in their environment. Understanding connectivity among seabird populations is crucial for their long-term conservation, and has been investigated in numerous studies of seabird species from around the world. Similar to many of these, this study found very low levels of genetic structure among populations of all three focal species based on DNA sequence data, suggesting long-term gene-flow among them, despite potential physical and non-physical barriers. Overall, the patterns observed suggest that high connectivity characterises their breeding regions, and most breeding colonies, buffering the respective populations against environmental variability. These results were supported by fine-scale analyses of the African Penguin using microsatellite markers that also suggested high levels of gene-flow, which may have masked genetic signatures of the regional- and colony-level bottlenecks experienced by this species. Microsatellite-based genetic diversity and fine-scale structure were also compared among wild and captive populations of African Penguins to assess the genetic consequences of a planned conservation breeding program. The genetic composition of birds in captivity largely reflects that found in wild populations. The success of reintroduction in terms of decreasing extinction risk in the wild is uncertain, and should be implemented as part of a broader management plan that addresses the primary threats to wild populations. Further research is required to improve our understanding of many aspects of endemic southern African marine avifauna and better inform our ability to ensure their continued persistence in this system.