Feeding association between cattle egrets (<i>Bubulcus ibis<i/>) and mammal hosts in the central Free State

Field observations undertaken during October 1995 to April 2001 in agricultural areas and nature reserves of the central Free State, indicate that cattle egrets mainly feed in commensalistic association with ungulates or even farm implements. A higher percentage farm animals than game was involved herewith. Based on calculated preference indices only three species, namely cattle, buffalo and white rhino, qualified as key hosts. Eland, gemsbok, impala and horses were classified as major hosts, while the rest of the thirteen observed host species were identified as minor hosts. More than half of all feeding associations (58,4%) occurred during the early mornings followed by a decrease during the middle of the day with a slight increase again later in the afternoon. Depending on the host species involved, notable differences occurred in the time of association. Cattle were the only host species with which cattle egrets associated during any time of the day. Evidently, cattle egrets associated most often with larger host species which were actively grazing. In grassland habitats the birds mainly fed in front of grazing hosts, but behind those that moved too fast

Population structure of <i>Argas arboreus<i/> (Acari : Argasidae) ticks associated with seasonally abandoned mixed heronries, dominated by cattle egrets (<i>Bubulcus ibis<i/>), in South Africa

During winter populations of Argas arboreus from heronries of the cattle egret, Bubulcus ibis, in South Africa are composed of adults, with some predominance of males, and II-IV instar nymphs, in a state of diapause. The period of tick activity, including reproduction and development of eggs, larvae and N1 nymphs, is synchronized with the nesting and breeding season of their avian hosts. It begins during spring with the return of birds to the heronry, and ceases in autumn through induction of reproductive diapause in engorged females, and behavioural diapause in unfed nymphs and adult ticks. Many ticks showed morphological anomalies and malformations, the study of which could possibly be used for monitoring of environmental pollution

Population structure of Argas arboreus (Acari: Argasidae) ticks associated with seasonally abandoned mixed heronries, dominated by cattle egrets (Bubulcus ibis), in South Africa

During winter populations of Argas arboreus from heronries of the cattle egret, Bubulcus ibis, in South Africa are composed of adults, with some predominance of males, and II-IV instar nymphs, in a state of diapause. The period of tick activity, including reproduction and development of eggs, larvae and N₁ nymphs, is synchronized with the nesting and breeding season of their avian hosts. It begins during spring with the return of birds to the heronry, and ceases in autumn through induction of reproductive diapause in engorged females, and behavioural diapause in unfed nymphs and adult ticks. Many ticks showed morphological anomalies and malformations, the study of which could possibly be used for monitoring of environmental pollution.The articles have been scanned with a HP Scanjet 8300; 600dpi, saved in TIFF format. Adobe Acrobat v.9 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

The distribution and abundance of chironomids in high-latitude Eurasian lakes with respect to temperature and continentality: development and application of new chironomid-based climate-inference models in northern Russia

The large landmass of northern Russia has the potential to influence global climate through amplification of climate change. Reconstructing the climate in this region over millennial timescales is crucial for understanding the processes that affect the climate system. Chironomids, preserved in lake sediments, have the potential to produce high resolution, low error, quantitative summer air temperature reconstructions. Canonical correspondence analysis (CCA) of modern surface sediments from 100 high-latitude lakes, located in northern European Russia to central Siberia, showed chironomid distribution was primarily driven by July air temperatures. The strong relationship enabled the development of chironomid-inference model based on 81 lake and 89 taxa to reconstruct July air temperature. Analysis of a range of chironomid-inferred temperature model suggest the best to be a two component weighted averaging and partial least squares (WA-PLS model) with r2jack = 0.92 and RMSEP = 0.89°C. Comparison of species responses to July temperature with the Norwegian training set showed the temperature optima of individual species was 1-3°C in the Russian data regardless of modelling technique. This suggests that chironomid-based inference models should only be applied to sediment cores collected within the geographic source area of the training set. The differing responses between the Norwegian and Russian faunas led to the development of a 149 lake, 120 taxa chironomid-continentality inference model. The 2-component WA-PLS model was the minimal adequate model with r2jack = 0.73 and RMSEP = 9.9. Recent warming in the Arctic has been spatial and seasonal heterogeneous; in many areas warming is more pronounced in the spring and autumn leading to a lengthening of the summer, while summer temperatures have remained relatively stable. A continentality model has the potential to detect these seasonal changes in climate. The Russian inference model also improves the representation of a number of taxa, such as Corynocera oliveri-type, Constempellina and Paracladius, which frequently occur in subfossil assemblages from arctic Russian lakes, but are poorly represented in European training sets. These are cold-adapted taxa and their absence from the training sets could lead to overestimations of July temperatures in fossil samples where these taxa form a major component (for example see Andreev et al. 2005). Comparison of reconstructed July air temperatures and continentality indices from a tundra lake in north-east European Russia showed close agreement with local instrumental records over the past 70 years and suggests the models may produce reliable estimates of past climate

Macrofossils in Raraku Lake (Easter Island) integrated with sedimentary and geochemical records towards a palaeoecological synthesis for the last 34,000 years

Macrofossil analysis of a composite 19 m long sediment core from Rano Raraku Lake (Easter Island)was related to litho-sedimentary and geochemical features of the sediment. Strong stratigraphical patterns are shown by indirect gradient analyses of the data. The good correspondence between the stratigraphical patterns derived from macrofossil (Correspondence Analysis) and sedimentary and geochemical data (Principal Component Analysis) shows that macrofossil associations provide sound palaeolimnological information in conjunction with sedimentary data. The main taphonomic factors in fluencing the macrofossil assemblages are run-off from the catchment, the littoral plant belt, and the depositional environment within the basin. Five main stages during the last 34,000 calibrated years BP (cal yr BP) are characterised from the lithological, geochemical, and macrofossil data. From 34 to 14.6 cal kyr BP (last glacial period) the sediments were largely derived from the catchment, indicating a high energy lake environment with much erosion and run-off bringing abundant plant trichomes, lichens, and mosses into the centre of Raraku Lake