SE Kenya Research Articles

Lukea gen. nov. (Monodoreae-Annonaceae) with two new threatened species of shrub from the forests of the Udzungwas, Tanzania and Kaya Ribe, Kenya

SummaryA new genus, Lukea Cheek & Gosline (Annonaceae), is erected for two new species to science, Lukea quentinii Cheek & Gosline from Kaya Ribe, SE Kenya, and Lukea triciae Cheek & Gosline from the Udzungwa Mts, Tanzania. Lukea is characterised by a flattened circular bowl-shaped receptacle-calyx with a corolla of three free petals that give the buds and flowers a unique appearance in African Annonaceae. Both species are extremely rare shrubs of small surviving areas of lowland evergreen forest under threat of habitat degradation and destruction and are provisionally assessed as Critically Endangered and Endangered respectively using the IUCN 2012 standard. Both species are illustrated and mapped. Material of the two species had formerly been considered to be possibly Uvariopsis Engl. & Diels, and the genus Lukea is placed in the Uvariopsis clade of the Monodoreae (consisting of the African genera Uvariodendron (Engl. & Diels) R.E.Fries, Uvariopsis, Mischogyne Exell, Dennettia Baker f., and Monocyclanthus Keay). The clade is characterised by often conspicuous, finely reticulate quaternary nervation, incomplete or absent connective shields (in Annonaceae the connective shield is usually complete) and free petals (except in some Uvariopsis). Morphologically Lukea is distinct for its broad, turbinate, fleshy pedicel, a potential synapomorphy within Monodoreae. It appears closest morphologically to the West African monotypic Monocyclanthus, since it shares a trait unusual in the Annonaceae: the calyx in both genera forms a shallow bowl (calyx lobes are absent or vestigial), barely enclosing the base of the petals at anthesis, which persists, living and green, in the mature fruit. However, on recent molecular phylogenetic evidence, Lukea is sister to Mischogyne and the two split c. 20 million years BP, while Monocyclanthus is sister to Dennettia. The placement of Lukea within the Uvariopsis clade is discussed.

Source controls on sulfur abundance and isotope fractionation in hydrothermal fluids in the Olkaria geothermal field, Kenya

Sulfur is among the major components in volcanic hydrothermal fluids and may derive from multiple sources. However, processes such as boiling, magma degassing, fluid-rock interaction and associated redox reactions often obscure the origin of sulfur in the system. The multiple sulfur isotope system is a powerful tool to unravel the processes that affect isotope ratios of sulfur in geothermal systems. Here, we utilized concentrations and multiple isotope ratios (32S/33S/34S/36S) of sulfur from well discharge from geothermal fields at Olkaria, SE Kenya, to investigate the hydrothermal processes and to quantify the sources of sulfur to the system. Fluid sampling temperatures ranged from 157 to 204 °C, and the sampled fluids had low Cl concentrations (119 to 1267 ppm Cl) with both liquid water and vapor being present. The concentration of H2S and SO4 in the water phase of the well discharges ranged from 0.53 to 68.0 ppm and from 4.7 to 108 ppm, respectively. In the vapor phase, H2S was the only observed sulfur compound with concentrations between 1.18 and 214 μmol mol−1. In the water phase, δ34S values for H2S and SO4 ranged from −1.2 to +4.0‰ and +0.7 to +7.7‰, respectively. The δ34S values of H2S in the vapor phase ranged from +2.0 to +11.3‰. The Δ33S values for H2S in the water and vapor phase were found to be between −0.017 and +0.021‰ and −0.042 and +0.008‰, respectively, and for SO4 in the water phase between −0.024 and + 0.004‰. Sulfur isotopes of H2S in liquid phase were depleted in 34S as a result of depressurization boiling. Sulfur isotope ratios as well as the results of geochemical modelling suggest that sulfide in the fluids dominantly originated from rock leaching where insignificant amounts of sulfur was derived from direct degassing of a magmatic source. Sulfate primarily derived from the oxidation of H2S to SO4 upon fluid ascent to the surface. Based on the geochemical model results and measured sulfur concentrations, the annual natural H2S emission rate at Olkaria was estimated to range from 320 to 510 t H2S yr−1. These comparatively low sulfur emissions and the lack of significant sulfur sources (e.g., magma or seawater) imply that Olkaria could represent an ideal re-injection site for anthropogenic H2S even if sulfur sequestration rates would be low.

Application of Remote Sensing in Mapping Hydrothermal Alteration Zones and Geological Structures as Areas of Economic Mineralization in Mwitika-Makongo Area, SE Kenya

Remote sensing investigations combined with Geographical investigation systems (GIS) have become more important for the study of geological mineralization and structural geology like lineaments. Automatic extraction of lineaments from satellite imagery help in giving an overview of the tectonic events in the study area. The main objective of the study was to map hydrothermally altered rocks and geological structures that may be associated with mineral deposits in Mwitika-Makongo area. The study involves the use of Landsat- 8/OLI image. The satellite images were classified using ENVI 5.3 and ArcGIS 10.5. PCI geomatics 2016 was used for extraction of lineaments while Rose diagram was generated using Rockworks 16. Different remote sensing techniques, such as colour composite, band ratio and principal component analysis were applied to identify geological units and features related to economic mineralization. Colour composite band combination (5, 6, 7) showed hydrothermally altered geological units as blue. Band ratio combination (4/2, 6/7, 6/5) showed the areas that were hydrothermally altered as blue. Lineament mapping was done using PCA, with the first three PCs having the highest percentage of Eigenvalues. A lineament density map showed higher values in Makongo hill followed by Kalima Kathei hill. The structural trend from the rose diagram is in the NE direction. The results of image analysis and lineament extraction show that the economic minerals like iron ore are located in areas of hydrothermal alterations where intrusive rocks like Pyroxenite were found. Keywords: Colour composite, Geographical investigation systems, Landsat- 8/OLI, Lineaments, Principal component analysis, hydrothermally altered. DOI : 10.7176/JEES/9-11-03 Publication date: November 30 th 2019

Genetic significance of the 867 cm− 1 out-of-plane Raman mode in graphite associated with V-bearing green grossular

SE Kenya is the world’s largest producer of green vanadium grossular gemstones (tsavorite). Samples from one of the mines near Mwatate, and of occurrences in Tanzania yielded remarkable new insights into the genesis of tsavorite. Graphite is intimately associated with V-grossular and is one of the keys to understanding its origin. In the course of this study we found five different types of graphite. Surprisingly, in one graphite type the “Raman-forbidden” and IR-active 867 cm− 1 band was observed. In this communication, we attempt to find an explanation for this unusual phenomenon. Additionally, our observations also address some of the issues pertaining to the origin of the green grossular-dominated rocks (grossularites), as well as the gem quality tsavorite crystals, since we propose that the anomalous spectroscopic behavior of the graphite is related to the unusual conditions during crystallization of both the grossular and graphite from a near-supercritical volatile- and sulfur-rich silicate melt. The massive green vanadium grossular contains abundant unequivocal crystallized melt inclusions, while the transparent gem quality grossular (tsavorite) displays only fluid inclusions. On the basis of inclusion studies we suggest that anatectic melts originated in the peculiar evaporitic host lithology of the tsavorite deposits. Near peak metamorphic temperatures (~ 700 °C) these liquids occurred as a supercritical volatile-rich “fluid/melt phase” characterized by complete miscibility between H2O and silicate liquid. Relatively dry liquid batches precipitated non-transparent green grossular, whereas wet batches segregated fluids that formed transparent tsavorite.

Environmental factors affecting the distribution of African elephants in the Kasigau wildlife corridor, SE Kenya

AbstractThe African elephant, Loxodonta africana, is under threat from habitat loss, poaching and human–elephant conflict. To mitigate for impact of habitat loss and reduce conflict, connectivity between elephant habitats can be improved through the protection of corridor areas. This study looks at elephant distribution and movement patterns within the Kasigau Wildlife Corridor (KWC) within the Tsavo Conservation Area in South‐east Kenya. Elephant presence data were obtained from observations by rangers during routine patrols across KWC, and were analysed in MaxEnt. The environmental factors predicting elephant distribution and density were tested, as well as the relationship between elephant maximum entropy and the presence and abundance of other wildlife. Seasonal variations in temperature and precipitation, plus presence of waterholes were found to play significant roles in elephant distribution across KWC. Higher elephant densities were not found to correlate with lower densities of other wildlife species; indeed, during the dry seasons, elephant presence was associated with greater wild herbivore densities. Besides illustrating the importance of the KWC for elephant conservation in the Tsavo ecosystem, both as a key corridor and habitat, this study also hopes to highlight the untapped utility of routine ranger patrol data, and encourage the use of such presence‐only data for deducing important knowledge for conservation of biodiversity.

Age and hafnium isotopic evolution of the Didesa and Kemashi Domains, western Ethiopia

The Western Ethiopian Shield (WES) forms a vast, underexplored, region of the East African Orogen. Lying towards the west of the orogen and between the dominantly juvenile Arabian-Nubian Shield in the north and the high-grade Mozambique Belt to its south, it holds a key position; vital in understanding the role of the East African Orogen in Gondwana formation. The WES is made up of a range of supra-crustal and plutonic rocks that formed in Tonian volcanic arc environments. The relative timing and duration of arc formation within the East African Orogen is still slowly being unravelled and we present new U-Pb and Hf isotopic data from zircons that help to define the maximum depositional age and provenance of the protoliths to meta-sedimentary units, as well as constrain the age of igneous intrusions located within the WES. Detrital zircons, obtained from a meta-sandstone, yield provenance age peaks at 2.8–2.4Ga, ca. 1.8Ga and 1.15–0.84Ga and a maximum depositional age of 838±13Ma. Hafnium isotopes from the same zircons demonstrate that both the oldest and youngest populations have broadly juvenile Hf isotopic values. However, the ca. 1.8Ga population shows significantly evolved Hf isotopic values. Sensitive High Resolution Ion MicroProbe (SHRIMP) U-Pb ages from two granites and a felsic granite and hornblende+biotite tonalite in the Nekempt–Ghimbi region of the Western Ethiopian Shield (Didesa and Kemashi Domains) indicate two pulses of magmatism at 850–840Ma and 780–760Ma. Partial melting and deformation in the Didesa Terrane occurred at ca. 660 Ma. Further west, the post-tectonic Ganjii granite yielded a 206Pb/238U age of 584±10Ma, constraining pervasive deformation in the area.Age constraints on orogenesis in the Western Ethiopian Shield (ca. 660Ma) are similar to those in NE Uganda (ca. 690–660Ma), but are older than the Ediacaran peak orogenesis reported from the Southern Ethiopian Shield, Eritrea and northern Ethiopia and from SE Kenya. This suggests that closure of the western Mozambique Ocean involved progressive volcanic-arc accretion to the active margin of Cryogenian–Ediacaran Africa.

Trees in a human-modified tropical landscape: Species and trait composition and potential ecosystem services

Worldwide, large areas of the tropics are transformed into simplified ecosystems characterised by altered tree species composition and diversity. Human activities in these landscapes have a strong effect on the land cover and exert a selective force on tree species and functional traits, hereby potentially shaping the distribution of ecosystem services in the landscape. The aim of this study was to asses how the land use determines tree species assemblages, their associated traits and potential ecosystem services, which was studied for 589 systematically sampled locations in the Afromontane highlands of Taita Hills (SE Kenya). Several tree traits were non-random distributed in the human-dominated landscape. For instance, on croplands (70% of the sampled locations) belonged 66.5% of the observed species to the exotic tree species group. This group was characterised by significantly larger seeds and fruits, corresponding with the abundance of many fruit trees. Also three functional traits (i.e. economic function, nitrogen fixation and agroforestry potential) were clearly associated with this group. The cloud forest tree species group and small-leaved indigenous group were significantly more present on woodes sites and homesteads (∼42%). However, no functional traits were unique for both indigenous groups, implying that farmers may exchange them by exotics, which could be catalysed by the loss of local knowledge about indigenous tree resources and benefits. Other indigenous species, including endemic or late-successional species were rare or absent in the matrix and their conservation can only be guaranteed by protecting the remaining indigenous forest fragments.

Integration of Geological Mapping and Remote Sensed Studies for the Discovery of Iron–Ore Mineralization in Mutomo–Ikutha Area, SE Kenya

This research integrates geology with remote sensing techniques to establish characteristic features that can be used to discover iron ore mineralization within the Neoproterozoic rocks of Mutomo - Ikutha area in south eastern Kenya. The association of hornblende gneiss and shearing as well as alteration processes near the mineralized regions appear to play an important role in the distribution and localization of the iron mineralization The methods used in this research include Image processing techniques applied on the digital subset ETM+ data that cover Mutomo - Ikutha area and geological field mapping. These techniques generated several products of enhanced satellite imagery, such as colour composite images, ratio images and principal component images. These techniques have been successfully used in the lithological discrimination of iron ore bearing sheared hornblende gneisses. The capabilities of remote sensing data to characterize the iron ore bearing gneisses, in addition to characterization and mapping the hydrothermal alteration zones helped in identification of iron mineralization regions. Extensive field geologic and geochemical investigations to the pronounced zones delineated by the image processing technique, led to discovery of four locations of high iron anomalies with some iron mineralization, mainly connected to the studied Neoproterozoic hornblende gneisses. Chemical studies were carried out using atomic absorption spectrophotometer (AAS) and X-Ray florescence, for some selected mineralized samples. Petrographic analysis and physical properties of the iron minerals were carried out as well. These investigations confirm the present iron mineral to be magnetite ore enriched with phosphates. The magnetite is found in close association with apatite chalcopyrite, quartz, and chlorite. Relics of corroded magnetite grains are occur along the Tiva river bed as well as along the road sides.

Application of Magnetic Survey in the Investigation of Iron Ore Deposits and Shear Zone Delineation: Case Study of Mutomo-Ikutha Area, SE Kenya

The main objective of this research was to use ground magnetic survey to delineate shear zone and iron ore deposit within the Neoproterozoic rocks of Mutomo-Ikutha area of south eastern Kenya. Total field magnetic data was recorded by using high resolution proton precision geometric magnetometer which recorded total components of the ground magnetic anomaly data running through sixteen traverses. The field data was qualitatively and quantitatively interpreted and the results gave values for the total component measurements of ground magnetic anomaly that varied between a minimum negative peak value of about 250 nanoTesla and a maximum of about 1000 nanoTesla. 550 nanoTesla was considered to be threshold of the iron mineralization within the area. The results indicated that the western part of Mutomo-Ikutha was sheared, faulted and contained iron ore mineralization trending in the north-south direction. Areas with high anomalous values were geochemically proven to contain magnetite.

Petroleum Prospects of Lamu Basin, South-Eastern Kenya

Abstract: The hydrocarbon potential of the sub-surface Lamu basin (SE Kenya) offshore sedimentary rock sequences of Mesozoic age formed the premise of this study. Major similarities and some differences in structural styles can be seen between the offshore Lamu and the Gondwana basins along the margins of Indian Ocean and Carnarvon basin along Australia’s North West Shelf, where oil pools have been discovered. The existing well results and recent 2-D seismic data have been interpreted to identify various structural styles and play fairway segments, which bolster the possibility that the Karroo to late Tertiary sedimentary mega-sequences (∼3000 – 13000 m thick), suitable for hydrocarbon exploration, could be visualized in both the onshore and offshore Lamu basin areas. Similarly, major reservoir-seal and potential source intervals have been identified in the present study. The hydrocarbon indicator from the well-log data shows that oil potential in complex multiple petroleum systems, ranging in age from Triassic to Tertiary, have tested gas deposits. Well control of only one exploratory well per 25,000 sq km in the offshore Lamu basin shows evidence of the existence of at least two active petroleum systems. The Lamu basin has evolved consequent to a complex tectonic activity related to continental rifting and block faulting of the Lamu-Anza and Central African rift systems. An attempt has been made to recommend the probable prognostic structural leads, which are controlled by NW-SE trending faults sympathetic to the Anza-Lamu rift systems, for future essential sub-surface features of source rocks, reservoir rocks and the cap rocks in the Lamu basin.

Additions to the moss flora of the Taita Hills and Mount Kasigau, Kenya

Abstract Based on our recent collections we report 43 moss species as new to the Taita Hills and Mount Kasigau in SE Kenya, 15 of the species being also new to the country. The number of moss species known from the region rises from the previously reported 85 to 128, and from 506 to 521 for the whole country. The most noteworthy findings are Fissidens splendens Brugg.-Nann., previously known only from Tanzania, and Barbella capillicaulis (Renauld & Cardot) Cardot var. capillicaulis (Renauld & Cardot) Cardot, previously reported from Mauritius, Madagascar and Uganda. The taxa reported represent the families Anomodontaceae (1 sp.), Brachytheciaceae (3 spp.), Calymperaceae (3 spp.), Dicranaceae (8 spp.), Erpodiaceae (1 sp.), Fissidentaceae (3 spp.), Hedwigiaceae (1 sp.), Hookeriaceae (1 sp.), Hypnaceae (3 spp.), Leucodontaceae (1 sp.), Meteoriaceae (3 spp.), Neckeraceae (5 spp.), Orthotrichaceae (1 sp.), Pilotrichaceae (1 sp.), Polytrichaceae (1 sp.), Pterigynandraceae (1 sp.), Pterobryaceae (2 spp.), Pylaisiadelphaceae (1 sp.), Sematophyllaceae (1 sp.), Stereophyllaceae (1 sp.), and Thuidiaceae (1 sp.).

Unsustainable charcoal production as a contributing factor to woodland fragmentation in southeast Kenya

Drawing from a holistic research approach, this paper contributes to the studies of land cover change and sustainable development in Kenya, and to the planning of sustainable future in Dakatcha Woodland, SE Kenya. As an un-protected global hotspot for biodiversity, Dakatcha Woodland has suffered from unsustainable forest resource use. The relation of charcoal production to land cover change and its socio-economic impact are studied in detail. A supervised land cover classification formed using four SPOT satellite images from 2005/06 and 2011 revealed that the woodland is fragmenting and the Important Bird Area (IBA) demarcation should be reconsidered. Through in-situ observation, household questionnaires and semi-structured expert interviews it was found that more than half of the 90 households assessed are involved in charcoal production which is higher figure than peer studies have suggested, and that the charcoal network offers income to many, but bears an negative impact on the environment. It was discovered that, like in Kenya, in Dakatcha Woodland, too, the demand for woodfuels (charcoal and fuelwood) is one of the key drivers of deforestation and land degradation. As such, woodfuel energy is a cross cutting issue, tying together forest resources, livelihoods and sustainable development, and thus demands further research. Forest management of Dakatcha Woodland must be planned in accordance with all stakeholders in a sustainable manner, drawing from agroforestry and participatory forest management systems, and keeping environmental factors in mind for the maintenance of ecosystem services.

Making sense of abstinence: social representations in young Africans' HIV-related narratives from six countries

Despite the prominence of abstinence promotion in HIV prevention for young Africans, there is little documentation concerning its reception and interpretation. With the purpose of informing programmatic practice, we examined how young Africans from six countries with contrasting HIV prevalence rates make sense of abstinence. ‘Scenarios from Africa’ scriptwriting contests invite young people to contribute ideas for short films about HIV. Using thematic narrative-based approaches, we analyzed a stratified random sample of these narratives written in 2005 by young women and men aged 10–24 years from Senegal, Burkina Faso, South-East Nigeria, Kenya, Namibia and Swaziland. Abstinence was considerably more prominent as a theme in the samples from SE Nigeria, Kenya and Swaziland. It was articulated in relation to conservative Christian sexual morality and in opposition to condom use with particular intensity in SE Nigeria, with stigmatising implications for non-abstainers. However, cross-national commonalities were more striking than differences. Examples of non-stigmatising pro-abstinence messaging highlighted the appeal of discourses of romantic love and future plans across countries and demographic characteristics. The analysis yielded contextual understanding, youth-driven ideas and recommendations to inform comprehensive HIV-prevention efforts.

Using science to guide conservation: From landscape modelling to increased connectivity in the Taita Hills, SE Kenya

Using science knowledge to guide conservation action remains difficult; communication gaps persist, especially between scientists and other stakeholders including policy makers. Here, we demonstrate how we have managed to integrate scientific knowledge into consensually formulated conservation actions in the Taita Hills, Kenya. GIS-based least-cost modelling, together with sociological and forest characteristics were used to determine and prioritise the most appropriate areas for reforestation from a set of exotic forest plantations targeted for conversion into indigenous forests. This prioritisation was done through a succession of three workshops (on site) used to reach multiple stakeholders, build consensus on conservation actions, and formulate an implementation framework. Indigenous tree nurseries have now been established to provide planting stock for the reforestation activities agreed upon after the final workshop. The key lesson we learned from this exercise was that bridging the gap between science and conservation demands a very open, inter-disciplinary strategy, initiated and executed jointly by a diverse group of people that includes the Government (policy-makers and implementers), NGOs (conservationists and environmental advocates), scientists (researchers), conservationists and the local community. This study provides a pointer for what it may take to integrate human issues with sustained environmental management based on scientific knowledge.

Geochemistry of basement rocks from SE Kenya and NE Tanzania: indications for rifting and early Pan-African subduction

Amphibolites and orthogneisses from the Taita Hills-Galana River area (SE Kenya) indicate their broad geological-tectonic setting. There are groups of subduction-related rocks which show characteristic REE (rare earth element) patterns and enrichment or varying concentrations of HFS (high field strength) elements. The groups can be assigned to tectonostratigraphic domains marked by different structural styles (e.g., thrust- or strike slip dominated). Tholeiitic gneisses, often emerging as folded and isolated (ridge-shaped) leucocratic bodies, belong to a group of rocks located between the thrust- and strike-slip domain. Compared to calc-alkaline gneisses of the area they contain more mafic inclusions and have lower LIL (large ionic lithophile), HFS and light REE values. These gneisses have chemical characteristics of M-type granitoids of oceanic island arc signature. Intrusion ages of ~955–845 Ma determined for these rocks suggest early Pan-African subduction. Mafic to ultramafic rocks from the Pare mountains of NE Tanzania show evidence of ophiolitic cumulates, subduction settings were also observed for the granulite areas in central and southern Tanzania. Together with the widespread arc settings documented in the Arabian–Nubian Shield, the presented data supports the continuation of an island-continental arc range across Kenya–Tanzania to Mozambique.

SHRIMP U–Pb zircon and Sm–Nd garnet ages from the granulite-facies basement of SE Kenya: evidence for Neoproterozoic polycyclic assembly of the Mozambique Belt

The Taita Hills–Galana River region is a key area to demonstrate the polycyclic nature of the Mozambique Belt in SE Kenya. On the basis of petrological and tectonic data, this area is composed of two different granulite-facies terranes, which are separated by the 20–30 km wide Galana Shear Zone. The Taita Hills and adjoining Sagala Hills exhibit a metamorphic overprint at 630–645 Ma, similar to areas in Tanzania. An emplacement age for the magmatic precursor rocks of 850–960 Ma was derived from zircon cores. Sm–Nd garnet–whole-rock analyses give an age of 585 Ma, interpreted as the cooling age after 630–645 Ma metamorphism. Nd crustal residence ages are between 1000 and 1500 Ma. The Galana Shear Zone east of the Taita Hills contains strongly deformed tonalitic migmatites with interlayered pegmatites that date a younger tectonometamorphic event at 560–580 Ma. East of the shear zone only a young metamorphic age of 550 Ma was found. The Nd model ages are c . 1500 Ma to c . 2900 Ma. In a continental configuration prior to Gondwana break-up our study area was located close to Madagascar, where several large shear zones are observed. One of these shear zones (Ranotsara Shear Zone) may be a continuation of the Galana Shear Zone.

Application of fragmentation research to conservation planning for multiple stakeholders: An example from the Taita Hills, southeast Kenya

Attrition and fragmentation of natural habitats remains one of the most persistent problems for conservationists. Exactly how habitat loss leads to the loss of biodiversity is not easily pinned down, and varies across species, taxonomic groups and landscapes. Integrating theory with conservation on the ground is challenging due to the multi-faceted nature of the problem. Here, we briefly highlight and review key scientific results from an ongoing long-term ornithological research project in the highly fragmented and threatened forests of the Taita Hills, SE Kenya. The findings point to the inability of birds to disperse between remnant habitats, or to adjust to changing habitat quality as the main mechanisms underlying adverse effects of forest loss on birds. We integrated our findings and their implications for conservation in a recent stakeholders’ workshop bringing together scientists, government officials and members of the local community in the Taita Hills. During this workshop the local community and the government voiced their priorities concerning these forest resources, by identifying the pressing problems and suggesting best avenues of mitigating them. We discuss how the scientific results and recommendations from a biodiversity standpoint are being translated into actual conservation, taking into account the views and priorities of other key stakeholders. This exemplifies one of the few unique situations in eastern Africa where enormous effort is being made towards bridging the chronic gap between scientists, government and local communities concerning the conservation of natural resources. We believe that this approach holds great promise for achieving lasting conservation on the ground.

Annual Survival and Turnover Rates of an Afrotropical Robin in a Fragmented Forest

Whether or not subdivided populations persist in fragmented landscapes primarily depends on how well individuals can survive within discrete habitat patches. Using data from six capture–recapture sessions, survival probabilities of the white-starred robin were estimated in seven indigenous forest patches in the highly fragmented Taita Hills forests, SE Kenya. We found no significant differences in survival probability either among fragment-size categories (large 135 ha, medium 95 ha, and small 2–8 ha) or between adult and first-year birds. However, males had a higher probability of survival from one year to the next than females. Turnover rates of adult birds were higher for females than males, but also higher in the medium and small patches than in the large one within each sex. That survival probability was similar among fragments, but turnover rates differed denoted that different processes caused extirpation from the patches. We suggest that mortality associated with dispersal was probably a more important cause of extirpation than within-patch mortality in the largest habitat, which had the lowest turnover rates. Conversely, high within-patch mortality, for instance due to predation during incubation, could have been more important in the smaller, more disturbed habitats. These results lend support to the proposition that avian conservation efforts should be focussed both at the landscape level to improve connectivity between fragments and reduce mortality during dispersal, and at the patch level to exclude other mortality sources such as nest predation.

Exotic origin of the ruby deposits of the Mangari area in SE Kenya

The Proterozoic Mozambique Belt contains numerous primary deposits of gem-corundum (i.e., ruby and sapphire). The ruby deposits in the Mangari area of SE Kenya, are among the most productive and best known. Enclosed within a metasedimentary sequence dominated by sillimanite-graphitic gneisses, the Mangari deposits are associated with rootless ultrabasic bodies. Ruby occurs (1) in lenses on the inner side of the contacts between the ultrabasites and the surrounding metasediments and (2) in veins within the ultrabasic bodies or forming their margins. Field relationships reveal that the corundum-bearing rocks are genetically related to the ultrabasic bodies but not to the surrounding gneisses. Laboratory studies and petrographic comparisons indicate that the ruby-bearing rocks crystallized under granulite facies conditions of 700–750°C and 8–10.5 kbar. By contrast, the surrounding gneisses show only amphibolite facies metamorphism with maximum temperatures around 650°C and pressures which did not exceed 7 kbar. At Mangari, the ruby-bearing rocks, as their associated ultrabasites, appear to be exotic with respect to the surrounding metasedimentary rocks. We interpret them as fragments of a deeper crust brought up to their present-day exposure level by the ultrabasic bodies during their emplacement as thrust sheets. Similar reasoning may account for the presence of charnockitic gneisses nearby. By contrast, granulite facies metamorphism characterizes all rock types genetically relatable to the Tanzanian ruby deposits at Longido and Lossogonoi, both also situated in the Mozambique Belt. This suggests that, if associated with ultrabasites, primary deposits of rubies (and of subgem red corundum) formed only under granulite facies conditions in the Mozambique Belt. Some of these deposits were subsequently tectonically inserted into country rocks of lower metamorphic grade. This apparently occurred without the total fracturing of all crystalline gems.

Notes on the ecology of a suburban population of Rainbow lizards in coastal Kenya

Aspects of the ecology of a suburban population of rainbow lizards, Agama agama Linnaeus 1758, have been studied in Malindi, a coastal locality of SE Kenya. Four different family groups were monitored on a wall transect 120 m long. Each group constituted a dominant male (i.e. a brightly coloured and aggressive individual) and three to four adult females, but in one of the studied groups a subordinate male was also seen. Both sexes were active in the morning, and peak activity fell between 10.00 and 11.30 hours. Dominant males used elevated perches significantly more often than subordinate males and females. The diet consisted of terrestrial arthropods, and most of the prey eaten were beetles (6–8 mm long). The foraging strategy used by rainbow lizards was to eat small insects at very short time intervals. The lizards used sit‐and‐wait foraging, remaining motionless until the prey was <5 cm away. The rainbow lizards studied did not feed upon plant material.