OpenUCT :: Browsing by Department "FitzPatrick Institute of African Ornithology"

Browsing by Department "FitzPatrick Institute of African Ornithology"

Now showing 1 - 20 of 23

Open Access
Assessing sea turtle, seabird and shark bycatch in artisanal, semi-industrial and industrial of fisheries in the Cabo Verde Archipelago
(2020) Montrond, Gilson; Ryan, Peter; Jabado, Rima; Wanless, Ross
Firstly, I am very grateful to Birdlife International for the MSc scholarship. I am also very grateful to Professor Peter Ryan of the FitzPatrick Institute of African Ornithology, University of Cape Town, for agreeing to supervise this project and for his guidance, insights and comments on the write-up. I am grateful to Sarah Saldanha, for all the support during this MSc. Many thanks also to Dr Ross Wanless, Dr Rima Jabado and Ruben Rocha for all support, guidance and advice. I want to thank a lot Andy Angel for their accommodation and all support in South Africa. I am grateful to all the UCT staff and BirdLife Senegal Staff for all the support during this study. Many thanks to my family for all the encouragement and support. I want to thank to all the Cabo Verde fishers for their willingness to share their knowledge and experience. Finally, many thanks to the Conservation Biology class of 2019, for all their support.
Open Access
Assessing the climate change vulnerability of reptile and amphibian species found in Table Mountain National Park
(University of Cape Town, 2020) Harper, Jack; Cunningham, Susan; Foden, Wendy; Van Wilgen, Nicola
It is increasingly apparent that climate change and its associated impacts are a major threat to the rich biodiversity of the Cape floristic region. As the knowledge of the associations between biological traits and climate change impacts strengthens it has become clear that the assessment of climate change vulnerability is a key consideration in the management of biodiversity. This study is the first attempt to use a trait-based approach at the scale of a single national park, focusing on the climate change vulnerability of reptile and amphibian species found in Table Mountain National Park (including historically present species). The park and its immediate surrounding areas are home to a rich diversity of herpetofauna including the Critically Endangered Table Mountain ghost frog (Heleophryne rosei), Rose's mountain toadlet (Capensibufo rosei) and micro frog (Microbatrachella capensis), and the Endangered western leopard toad (Sclerophrys pantherina). Amphibian and reptile-specific assessment frameworks of biological and ecological traits were designed to identify the species most sensitive and least able to adapt to climate change pressures. Using a combination of a literature review and expert consultation, 18 species of amphibian and 41 species of reptile were assessed. The assessment highlighted that, in the worst-case scenario, 85% of the park's reptile species and 67% of the park's amphibian species are predicted to be highly vulnerable to climate change. The southern adder (Bitis armata), Cape long-tailed seps (Tetradactylus tetradactylus), Table Mountain ghost frog (Heleophryne rosei) and the Lightfoot's moss frog (Arthroleptella lightfooti) were identified as being the species most vulnerable to climate change within their respective taxa. All three of the Critically Endangered amphibian species were identified as having both high sensitivity and low adaptive capacity to climate change. Among the focal reptile species, climate change vulnerability was independent of current IUCN Red List status, highlighting that species currently not identified to be under threat by other anthropogenic pressures could imminently become threatened by climate change. Spatiallyexplicit presentation of the assessment output will help prioritise the management of areas within Table Mountain National Park that contain a high diversity of climate-vulnerable species. By reducing the threats from other human-associated impacts to these species, and by identifying when direct intervention is appropriate, the park's management can give these species the best opportunity of persistence in an uncertain climate future.
Open Access
Being cosmopolitan: evolutionary history and phylogeography of a specialized raptor, the Osprey Pandion haliaetus
(2015) Monti, Flavio; Duriez, Olivier; Arnal, Véronique; Dominici, Jean-Marie; Sforzi, Andrea; Fusani, Leonida; Grémillet, David; Montgelard, Claudine
BackgroundThe Osprey (Pandion haliaetus) is one of only six bird species with an almost world-wide distribution. We aimed at clarifying its phylogeographic structure and elucidating its taxonomic status (as it is currently separated into four subspecies). We tested six biogeographical scenarios to explain how the species’ distribution and differentiation took place in the past and how such a specialized raptor was able to colonize most of the globe.ResultsUsing two mitochondrial genes (cyt b and ND2), the Osprey appeared structured into four genetic groups representing quasi non-overlapping geographical regions. The group Indo-Australasia corresponds to the cristatus ssp, as well as the group Europe-Africa to the haliaetus ssp. In the Americas, we found a single lineage for both carolinensis and ridgwayi ssp, whereas in north-east Asia (Siberia and Japan), we discovered a fourth new lineage. The four lineages are well differentiated, contrasting with the low genetic variability observed within each clade. Historical demographic reconstructions suggested that three of the four lineages experienced stable trends or slight demographic increases. Molecular dating estimates the initial split between lineages at about 1.16Ma ago, in the Early Pleistocene.ConclusionsOur biogeographical inference suggests a pattern of colonization from the American continent towards the Old World. Populations of the Palearctic would represent the last outcomes of this colonization. At a global scale the Osprey complex may be composed of four different Evolutionary Significant Units, which should be treated as specific management units. Our study brought essential genetic clarifications, which have implications for conservation strategies in identifying distinct lineages across which birds should not be artificially moved through exchange/reintroduction schemes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0535-6) contains supplementary material, which is available to authorized users.
Open Access
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.
Open Access
Can we determine when marine endotherms feed? A case study with seabirds
(1992) WILSON, R; Cooper, J; Plötz, Joachim
The International Society for Burns Injuries (ISBI) has published guidelines for the management of multiple or mass burns casualties, and recommends that 'each country has or should have a disaster planning system that addresses its own particular needs.' The need for a national burns disaster plan integrated with national and provincial disaster planning was discussed at the South African Burns Society Congress in 2009, but there was no real involvement in the disaster planning prior to the 2010 World Cup; the country would have been poorly prepared had there been a burns disaster during the event. This article identifies some of the lessons learnt and strategies derived from major burns disasters and burns disaster planning from other regions. Members of the South African Burns Society are undertaking an audit of burns care in South Africa to investigate the feasibility of a national burns disaster plan. This audit (which is still under way) also aims to identify weaknesses of burns care in South Africa and implement improvements where necessary.
Open Access
Coevolution between brood-parasitic honeyguides and their hosts
(2020) Mcclean, Luke Alexander; Spottiswoode, Claire; Horrocks, Nicholas P C
Obligate brood parasites lay their eggs in the nests of other species, foisting the costs of parental care onto the host parents. The success of the parasite and host are then at odds, with both parties evolving defences and countermeasures in an evolutionary arms race. This reciprocal influence of acting upon both species' evolution — a process known as coevolution — has forged the natural world around us. Avian brood parasites and their hosts are now model systems for studying such coevolutionary interactions between species, providing striking examples of the adaptations that arise when the life histories of two species become entangled. In this thesis I highlight the adaptations that have arisen in response to coevolutionary selection pressures in a group of understudied avian brood parasites, the honeyguides (Indicatoridae), and their hosts. This study focuses on the greater (Indicator indicator) and lesser (I. minor) honeyguides, and their respective primary hosts, the little bee-eater (Merops pusillus) and the black-collared barbet (Lybius torquatus). The interactions between honeyguides and their cavity-nesting hosts of the Old World tropics are evolutionarily ancient, contrasting with the majority of studies of avian brood parasitism which have predominantly focused on temperate brood-parasitic species targeting open cup-nesting hosts. Therefore, honeyguides and their hosts are an ideal study system in which look for novel adaptations that have not evolved in other systems. Using field observations and experimental manipulations at each stage of the parasitic life cycle — before parasitism, during egg-laying, during incubation, and during chickrearing — I examine how honeyguides and their hosts have evolved in response to the selection pressures they exert on each other. First, in chapter two, I consider whether the nest structure of the little bee-eater – host to the greater honeyguide – can act as a defence against brood parasitism. Experimental manipulation of the size of bee-eater nest tunnels demonstrates that bee-eaters with narrower nest tunnels are less likely to be parasitized by greater honeyguides than those bee-eaters whose nests have wider nest tunnel entrances. This study provides the first experimental evidence of a host nest functioning as a frontline defence against brood parasitism. In chapter three, I take a comparative approach and use a phylogenetic framework to investigate, across multiple avian brood parasite species, the evolutionary drivers of rapid egglaying. This trait is shared by most brood-parasitic birds, but not by non-parasitic birds. I find strong evidence that the egg-laying speed of avian brood parasites is ecologically and physiologically constrained, but find no evidence that variation in the costs incurred duringparasitism events have driven variation in the rapidity of egg-laying among brood-parasitic species. In chapter four, I examine whether there are costs associated with the virulent egg puncturing behaviour of greater honeyguides, and whether honeyguides can adjust their level of virulence in accordance with these costs. I find strong support for the idea that virulence is costly to honeyguides, as bee-eater hosts are more likely to reject clutches that contained eggs punctured by honeyguides. Such punctured clutches are also more likely to be predated. Honeyguides appear to adjust how much they puncture host eggs in accordance with the severity of these costs, providing the first evidence of an avian brood parasite moderating its virulence in response to the associated costs. In chapter five, I examine egg rejection behaviour in the black-collared barbet, a common host of the lesser honeyguide. I consider whether the (smaller) size of a parasitic egg could be used as a cue for egg rejection inside the dark environment of a cavity nest. Through observations of natural parasitism events, and experimental parasitism of host nests using different sized eggs, I demonstrate that barbets are more likely to reject a clutch of eggs when they detect a small egg within the nest. This seems to be achieved through a process of true recognition, a mechanism that involves a specific innate or learnt template of what size eggs a host should reject. Barbets do not appear to rely on discordancy – comparing all eggs within their clutch in order to reject the odd one out – in order to make rejection decisions. Finally, in chapter six I explore whether honeyguides elicit additional provisioning from their foster parents by using vocal mimicry, and investigate why such extra food would be required. I demonstrate that both greater and lesser honeyguides mimic the sound of a brood of chicks of their respective hosts in order to receive higher levels of provisioning from their foster parents. I establish that greater and lesser honeyguides do this for contrasting reasons. Greater honeyguides require higher levels of provisioning to support their fast growth rate to a size much larger than their host siblings, whereas lesser honeyguides require more food in order to offset a sub-optimal diet provided to them by their foster parents.
Open Access
Collisions & biases: estimating the impact of low-voltage distribution lines on the Ludwig's Bustard (Neotis ludwigii)
(2012) Schutgens, Maurice; Ryan, Peter
Bird collision mortality associated with power lines is a global conservation challenge. The Ludwig's Bustard (Neotis ludwigii) population is probably declining throughout its range as a result of collisions with power lines. Collision estimates derived from periodic carcass counts along power lines are likely to be underestimates because of two main bias factors: scavenger and search bias. In this study 44 Egyptian geese (Alopochen aegyptiacus) and Spurwing geese (Plectropterus gambensis) were used as surrogates to explore the levels of the bias by conducting a scavenger trial (90-day period) and three search trials (conducted after 24 hours, 48 and 90 days). Scavengers had detected 88% and removed 11 % of carcasses after the first week, and only 14% of carcasses were removed by the end of the 90-day trial period. On average, observers located 70% of carcasses across the three trials with no clear pattern in detection rate over time. Scavenger bias and search bias for this site in the Karoo were calculated at 0.14 and 0.30 respectively. Five low-voltage distribution power line transects (approximately 99 km) were surveyed in the Namakwa District, South Africa, to calculate a crude collision rate for Ludwig's Bustard. A total of 22 Ludwig's Bustard carcasses were located and used to estimate an unadjusted collision rate of 0.27 km-1. / (95% Cl 0.03-0.29 km-1. /). This collision rate extrapolated across the 63,000 km of distribution lines crossing the bustard's range represents an annual mortality of 13,000 individuals. The bias adjusted collision rate estimate increased to 0.45 km-1 ./ (95% CI 0.04-0.48 km-1 f 1 ), which suggests 22,000 individuals are killed annually. The combined mortality of low-voltage and high voltage lines could be in the order of 32 000 individuals annually. Implementation of existing mitigation devices and research into additional measures are necessary to prevent further decreases of this endangered species.
Open Access
Effects of pine invasions on ground-dwelling ants on the southern slopes of the Swartberg Mountains
(1999) Chaane, Lovejoy; Dean, Richard; Richardson, David
Ant and plant assemblages in patches of Pinus species trees in mountain fynbos and renosterbos (Elytropappus rhinocerotis) shru.bland were investigated in order to detennine whether there were differences in ant and plant species richness, abundance and cover between patches of pines and the surrounding indigenous vegetation. The study was carried out in the Matjiesrivier valley on the southern slopes of the Swartrg mountains in the Oudtshoom district, South Africa. Ants were collected at three sites: one in an older (c. 70 years) pine patch in mesic mountain fynbos at about midslope and two in younger (c. 10 years) pine patches in closed and open remnant renosterbos shrublands respectively on lower slopes. On a per site basis, there were no major differences in ant and plant species richness between the pine and no-pine sites in renosterbos, or (with the exception of plants) the pine and no-pine site in mesic mountain fynbos. A total of 2 539 ants belonging to 37 species, distributed among 15 genera, were collected during the study. Camponotus was most species-rich genus (13 species), followed by Monomorium (7 species), Tetramorium (4 species) and Lepisiota (2 species), with 11 of the 15 genera each represented by a single species. No non-indigenous species were observed during the duration of the study. Camponotus sp.11, Lepisiota sp.1 and Tetramorium quadrispinosum were observed only in the open renosterbos site. Camponotus klugii, Camponotus sp. l, Camponotus sp. 6, Cerapachys sp. l, Meranoplus peringueyi, Monomorium fri.dae, Monomoriu1'Jl sp.3 and Technomyrmex albipes were observed only in the closed renosterbos. Camponotus bayneii, Camponotus sp.5, 7, 8 and 9, Crematogaster peringueyi, Pachycondyla pumicoca, Solenopsis punctaticeps and Tetramorium regulare were recorded only in mesic mountain fynbos The most abundant ant guild was the non-dominant generalist (17 species), particularly Pheidole sp. 1# (48 % of all individual ants) followed by nectar feeders (15 species), dominant generalists (2 species), specialist predators (2 species) and a seed harvester (1 species). In general, the non-dominant generalists preferred no-pine sites to sites invaded by pines. There was very little undergrowth under the pines in mesic mountain fynbos, and Clutia polygonoides, Cymbopogon sp. 1, Erica sp. 1, Metalasia cephalotes, Metalasia muricata, Pelagronium betulinum sp. 1 and Restio sp. 1 were significantly more frequent outside the patch. The two renosterbos sites showed no significant difference in Elytropappus rhinoceroti's cover in and out of pine patches, and only two species at the open rerttsterbos site, Dodonea sp. 1 and Re/hania squarrosa, were more abundant under pines than in the surrounding renosterbos. The most abundant plant life form was the ericoids (37 species) followed by proteiods (11 species), grasses (11 species), forbs (9 species) and succulents (4 species). In general, the five life forms did not show -any exclusive pattern of preference for either the pine or no-pine sites.
Open Access
Exploring the environmental drivers of waterfowl movement in arid landscapes using first-passage time analysis
(2016) Henry, Dominic A W; Ament, Judith M; Cumming, Graeme S
BackgroundThe movement patterns of many southern African waterfowl are typified by nomadism, which is thought to be a response to unpredictable changes in resource distributions. Nomadism and the related movement choices that waterfowl make in arid environments are, however, poorly understood. Tracking multiple individuals across wide spatiotemporal gradients offers one approach to elucidating the cues and mechanisms underpinning movement decisions. We used first-passage time (FPT) to analyse high spatial and temporal resolution telemetry data for Red-billed Teal and Egyptian Geese across a 1500km geographical gradient between 2008 and 2014. We tested the importance of several environmental variables in structuring movement patterns, focusing on two competing hypotheses: (1) whether movements are driven by resource conditions during the current period of habitat occupation (reactive movement hypothesis), or (2) whether movements are structured by shifts in the magnitude and direction of environmental variables at locations prior to occupation (prescient movement hypothesis).ResultsAn increase in rainfall at a 32day lag (i.e., prior to wetland occupancy), along with tagging site, were significant predictors of FPT in both waterfowl species. There was a positive relationship between NDVI and FPT for Egyptian Geese during this 32day period; the relationship was negative for Red-billed Teal. Consistent with findings for migratory grazing geese, Egyptian Geese prioritised food quality over food biomass. Red-billed Teal showed few immediate responses to wetland filling, contrary to what one would predict for a dabbling duck, suggesting high dietary flexibility. Our results were consistent with the prescient movement hypothesis.ConclusionsUsing FPT analysis we showed that the proximate drivers of southern African waterfowl movement are the dynamics of rainfall and primary productivity. Waterfowl appeared to be able to perceive and respond to temporal shifts in resource conditions prior to habitat patch occupation. This in turn suggests that their movements in semi-arid landscapes may be underpinned by intimate knowledge of the local environment; waterfowl pursue a complex behavioural strategy, locating suitable habitat patches proactively, rather than acting as passive respondents.
Open Access
Female begging calls reflect nutritional need of nestlings in the hen harrier Circus cyaneus
(2017) Redpath, Steve; Thompson, Alex; AMAR, ARJUN
BACKGROUND: Most birds exhibit bi-parental care with both sexes providing food for their young. Nestling signal food needs through begging. However, for some species, males rarely visit the nest, so have limited opportunity for gaining information directly from the chicks. Instead, females beg when males deliver food. We tested whether this calling signalled nutritional need and specifically the needs of the female (Breeder Need hypothesis) or that of their chicks (Offspring Need hypothesis). RESULTS: We observed begging and provisioning rates at 42 nests of hen harrier (Circus cyaneus) in Scotland, explored the factors associated with variation in begging rate and the relationship between begging and provisioning. We also tested the impact of food on begging and provisioning through a feeding experiment. Female begging rate increased up to a chick age of 3 weeks and then tailed off. In addition, begging increased when broods were large. CONCLUSIONS: Our data provided support for the Offspring Need hypothesis. At nests where adlib food was provided females reduced their begging rate. These patterns suggested that female begging was an honest signal of need. However, begging continued even with adlib food and was only weakly associated with greater provisioning by males, suggesting that these calls may also play an additional role, possibly reflecting sexual or parent-offspring conflict.
Open Access
How has woody vegetation changed in north-east Namibia in response to land use, climate and fire?
(2020) Eastment, Conor; Gillson, Lindsey; Humphrey, Glynis; Hoffman, Timm
Bush encroachment or the thickening of woody vegetation is a phenomenon occurring throughout savannas, which tends to be more pronounced in small protected areas. The consequences of bush encroachment are often negative for the conservation of biodiversity, for the promotion of tourism and the prevention of wildfires. Hence, effective monitoring of woody vegetation and the factors which influence its spread are essential. This is particularly the case for protected areas such as that of Bwabwata National Park (BNP) in north-east Namibia. With a complex land use history and different fire management approaches being adopted throughout the area, the effect of fire on woody vegetation in BNP is currently poorly understood. This study used a 20-year-old repeat photography monitoring project and satellite-based remote sensing products to explore woody cover dynamics in BNP. Results revealed that woody cover has increased by 13% since 1999 in BNP. Furthermore, the results show differences in the structure of woody vegetation. Repeated late dry season fires in the west of the park have driven an increasing dominance of 3m in eastern sections of the park. This influence of different fire regimes spatially across BNP, suggests that local fire management is a significant determinant of woody vegetation change. Woody vegetation change differs spatially across BNP due to frequent late dry season fires prevailing in the west and less frequent earlier season fires occurring in the east. Therefore, in order to reduce the mortality of woody species and conserve heterogenous height structure in the west, a reduction of frequent late dry season fires is required. Early dry season fires are shown to reduce the rate of increasing total woody cover change and, therefore, this fire management strategy arguably contributes towards the reduction of wildfire risk, conservation of biodiversity and promotion of tourism.
Open Access
How well do buffer circles capture the ranging behaviours of territorial raptors?
(2020) Brink, René; Amar, Arjun; Murgatroyd, Megan
As the world's human population increases, so does the competition for natural resources between humans and wildlife. This competition may be intense for apex predators, such as raptors, which generally require large natural areas in order to maintain their populations. Anthropogenic development within territories can cause individuals to either abandon these sites, reduce their breeding productivity, or cause direct mortality to the territory holding birds. To mitigate such impacts, one method, employed as part of Environmental Impact Assessments (EIA), is the use buffer circles centred on nest sites. Within these buffers the most damaging forms of development are prohibited. This approach assumes that raptors use the space around their nest in a uniform way, but this assumption may not always be correct and few have evaluated the effectiveness of buffer circles at protecting a species' home range. This study uses tracking data to evaluate the effectiveness of buffer circles to cover the ranging movements of six southern African raptor species, throughout the year, as well as during their breeding and non-breeding season. My study revealed that buffer circles whose dimensions were based on the species' 95% Kernel Density Estimate (KDE) did relatively well at capturing the proportion of individual GPS fixes, but did less well at capturing the KDE area from tracked birds. For buffer circles to capture 95% of the home range polygons (95% KDE) they would generally need to be at least twice as large as those that were derived from the 95% KDE home range area, and for some species with very large home ranges (e.g. Lappet-faced Vultures) even buffer circles that were 3 times the size failed to cover 95% of the KDE polygons.
Open Access
Identification of animal movement patterns using tri-axial magnetometry
(2017) Williams, Hannah J; Holton, Mark D; Shepard, Emily L C; Largey, Nicola; Norman, Brad; Ryan, Peter G; Duriez, Olivier; Scantlebury, Michael; Quintana, Flavio; Magowan, Elizabeth A; Marks, Nikki J; Alagaili, Abdulaziz N; Bennett, Nigel C; Wilson, Rory P
Accelerometers are powerful sensors in many bio-logging devices, and are increasingly allowing researchers to investigate the performance, behaviour, energy expenditure and even state, of free-living animals. Another sensor commonly used in animal-attached loggers is the magnetometer, which has been primarily used in dead-reckoning or inertial measurement tags, but little outside that. We examine the potential of magnetometers for helping elucidate the behaviour of animals in a manner analogous to, but very different from, accelerometers. The particular responses of magnetometers to movement means that there are instances when they can resolve behaviours that are not easily perceived using accelerometers.
Open Access
Is multiple nest building an adequate strategy to cope with inter-species nest usurpation?
(2016) Sumasgutner, Petra; Millán, Juan; CURTIS, ODETTE; Koelsag, Ann; AMAR, ARJUN
Abstract Background Black sparrowhawks (Accipiter melanoleucus) recently colonised the Cape Peninsula, South Africa, where the species faces competition for their nest sites from Egyptian geese (Alopochen aegyptiaca) which frequently usurp black sparrowhawk nests. In this paper, we test the hypothesis that multiple nest building by black sparrowhawks is a strategy to cope with this competitor, based on a 14-year long term data set. Results Two main results support the hypothesis: first, the numbers of intact nests per breeding season in black sparrowhawk territories increased as levels of geese interactions increased, specifically when usurpation occurred. Usurpation occurred significantly more often at nests later in the season, and may provide a further explanation for the advancement of the black sparrowhawk breeding season towards earlier breeding attempts which results in an overall extension of the breeding period (over 9 months) that has been found in our study population. Second, nest usurpation had a negative impact on black sparrowhawks’ reproductive performance at the ‘nest’ level, but not at the ‘territory’ level when multiple nests were available within the same breeding season, suggesting that this strategy was effective for dealing with this competitor. However, our results do not rule out long term negative consequences of these interactions, for example, reduced adult survival rates or reduced lifetime reproductive success, due to the higher energy demand required to build several nests each breeding season. Conclusions Our results suggest that black sparrowhawks avoid direct conflict with this large and aggressive competitor and instead choose the passive strategy in allocating more resources to multiple nest building. Our research further highlights the importance of behavioural plasticity, which might be especially important for city-dwelling species in the face of global urbanisation.
Open Access
Life on the edge: do body size and drinking dependency influence how birds deal with the heat in South Africa's most extreme desert?
(University of Cape Town, 2020) Orolowitz, Matthew; Cunningham, Susan J
Climate change-induced increases in air temperature pose a substantial risk to birds inhabiting arid environments. Terrestrial endotherms, such as birds, can respond to high temperatures by moving to cooler microsites, increasing heat dissipation behaviour and/or suppressing activity. Previous studies have suggested that larger bird species may have a greater suppression of activity (e.g. foraging) than smaller species at high air temperatures. However, this body mass effect may be confounded by drinking behaviour, since different species have diverse drinking ecologies. Using four species of lark that inhabit the Tankwa Karoo National Park, I investigated whether foraging activity and other heat-influenced behaviours were influenced by body mass or drinking behaviour when comparisons were constrained within a single family. These lark species were: Red-capped Lark (24 g), Spikedheeled Lark (25 g), Karoo Lark (29 g) and Large-billed Lark (45 g). There was a two-fold difference in body mass between the lightest (Red-capped Lark) and the heaviest (Large-billed Lark). Moreover, two of these lark species drink surface water (drinking larks; Red-capped and Large-billed Lark) and two do not (non-drinking larks; Spike-heeled and Karoo Lark). I also collected data on other passerines present in the Tankwa Karoo for comparison to the larks. Black bulb thermometers were used to measure the thermal landscape and a combination of instantaneous scan samples and focal observations to record bird behaviour. Black bulb temperatures were as much as 8.16 °C cooler in shaded than in sunny locations. Similarly, black bulb temperatures were as much as 8.02 °C cooler off the ground than on the ground. The results from scan sample data showed limited support that foraging was negatively correlated (although non-significant) with mass between lark species as temperatures increased; however, data from focal observations suggested larks that obtain all water from food had a greater reduction in foraging as temperatures increase than larks that drink free surface water. Within scan samples, heat dissipation and shade-seeking behaviour appeared to be more strongly influenced by whether the species drinks free surface water or not than by differences in body mass. Furthermore, drinking larks dissipate heat at lower temperatures and seek shade at higher temperatures than non-drinking larks. Foraging intensity was higher in the sunny microsites as compared to shaded microsites for all species, suggesting that drinking larks might gain an energetic benefit due to increased heat tolerance. Therefore, non-drinking species may be vulnerable to foraging-thermoregulation trade-offs under climate change. However, ongoing drying trends in the Tankwa Karoo and reduced availability of surface water may make drinking species more vulnerable to climate change in the future than non-drinking species.
Open Access
Meaningful call combinations and compositional processing in the southern pied babbler
(2016) Engesser, Sabrina; Ridley, Amanda R; Townsend, Simon W
Human language is syntactic in its nature: meaningful words are assembled into larger meaningful phrases or sentences. How unique this ability is to humans remains surprisingly unclear. A considerable body of work has indicated that birds are capable of combining sounds into large, elaborate songs, but there is currently no evidence suggesting that these structures are syntactic. Here, we provide important evidence for this ability in a highly social bird. Specifically, pied babblers combine two functionally distinct vocalizations into a larger sequence, the function of which is related to the function of its parts. Our work adds important evidence to the variation and distribution of combinatorial vocal mechanisms outside humans and provides insights into potentially early forms of human syntactic communication.
Open Access
Meta-population evidence of oriented chain migration in northern gannets (Morus bassanus)
(2012) Fort, Jérôme; Pettex, Emeline; Tremblay, Yann; Lorentsen, Svein-Håkon; Garthe, Stefan; Votier, Stephen; Pons, Jean Baptiste; Siorat, François; Furness, Robert W; Grecian, W James; Bearhop, Stuart; Montevecchi, William A; Grémillet, David
Although oriented migrations have been identified in many terrestrial bird species, the post-breeding-season movements of seabirds are generally regarded as dispersive. We used geolocator tags to reveal post-breeding movements and winter distribution of northern gannets (Morus bassanus) at a meta-population scale. By focusing on five breeding colonies of European gannets, we show that their breeding and wintering grounds are connected by a major flyway running along the coasts of Western Europe and Africa. Moreover, maximum winter distance to colony was similar across colonies despite their wide latitudinal range. In contrast with the general opinion that large pelagic birds such as gannets have unlimited ranges beyond the breeding season, our findings strongly suggest oriented chain migration in northern gannets (a pattern in which populations move uniformly southward) and highlight the benefit of meta-population approaches for studying seabird movements. We argue that the inclusion of such processes in ocean management plans is essential to improve efforts in marine biodiversity conservation.
Open Access
Population crash of an endemic South African cyprinid: the role of non-native fish, drought and other environmental factors
(2020) Cerrilla, Cecilia; Shelton, Jeremy; Paxton, Bruce; Schumann, Mandy; Reed, Cecile
Native freshwater fish are in decline worldwide due to human impacts including impoundment, changes to water quality, over-abstraction, climate change and the introduction of non-native species. South Africa's Cape Fold Ecoregion (CFE) harbours exceptionally high freshwater fish endemism, yet the majority of these species are threatened with extinction. The Clanwilliam sandfish (Labeo seeberi), an endangered cyprinid, has declined across its range in the CFE and currently exists in only a handful of tributaries of the Doring River in severely fragmented populations. The last remaining recruiting sandfish population occurs in the Oorlogskloof River, making this tributary one of critical conservation value. In this study, I analysed a six-year dataset comprising fish survey data from 38 sites along 25 km of the Oorlogskloof River to characterise spatio-temporal variation in sandfish abundance and size structure and evaluate the relative influence of different environmental factors on sandfish population trends. The environmental factors considered included other fish in the system, especially three non-native fishes (banded tilapia Tilapia sparrmanii, smallmouth bass Micropterus dolomieu and bluegill sunfish Lepomis macrochirus), temperature, precipitation, habitat characteristics and a range of physicochemical factors. The results show that sandfish have experienced a 93% decline in the sampled stretch of the Oorlogskloof River since 2013 and that the ongoing drought may be preventing recovery. They also suggest that banded tilapia do not adversely affect the Oorlogskloof River sandfish population, while predation of juveniles by smallmouth bass and/or bluegill sunfish apparently reduces the abundance of sandfish, especially of juveniles, where these non-native fish are present. Future studies should attempt to isolate the relative impacts of the different invasive fish species and examine habitat requirements of different sandfish life stages. Management of the river's sandfish population should focus on precautionary actions such as continued monitoring and landowner engagement, as well as clearing dams of non-native species high in the catchment, to prevent the further upstream invasion of smallmouth bass and bluegill sunfish. Proactive measures, such as eradicating smallmouth bass and bluegill sunfish from the Oorlogskloof River, are also necessary to restore connectivity of suitable sandfish habitat in the Doring River system.
Open Access
Protected areas as social-ecological systems: perspectives from resilience and social-ecological systems theory
(2017) Cumming, Graeme S; Allen, Craig R
Conservation biology and applied ecology increasingly recognize that natural resource management is both an outcome and a driver of social, economic, and ecological dynamics. Protected areas offer a fundamental approach to conserving ecosystems, but they are also social-ecological systems whose ecological management and sustainability are heavily influenced by people. This editorial, and the papers in the invited feature that it introduces, discuss three emerging themes in social-ecological systems approaches to understanding protected areas: (1) the resilience and sustainability of protected areas, including analyses of their internal dynamics, their effectiveness, and the resilience of the landscapes within which they occur; (2) the relevance of spatial context and scale for protected areas, including such factors as geographic connectivity, context, exchanges between protected areas and their surrounding landscapes, and scale dependency in the provision of ecosystem services; and (3) efforts to reframe what protected areas are and how they both define and are defined by the relationships of people and nature. These emerging themes have the potential to transform management and policy approaches for protected areas and have important implications for conservation, in both theory and practice.
Open Access
The causes of avian extinction and rarity
(1997) Lennard, Christopher James; Hockey, Phil
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.

Browsing by Department "FitzPatrick Institute of African Ornithology"

Results Per Page

Sort Options