Two sympatric Phoebetria albatrosses, P. fusca and palpebrata breeding at Marion Island in the South Indian Ocean were studied. Adult individuals were tracked between 2008 and 2011. The study examined the foraging distribution of the two species in relation to environmental parameters such as sea surface temperature. Interaction with mesoscale features expressed by sea surface temperatures, was tested with statistical models. Tracked P. fusca demonstrated positive association with sea surface temperatures in the Southern Indian Ocean, in particular during incubating and chick-provisioning periods, by travelling shorter distances to the interfaces of mesocale features created as a result of the Agulhas Return Current located << 500 km to the north of breeding islands. During nest construction, tracked P. fusca travelled greater distances in search of food possibly because they had no chick to return to at the colonies. Contrastingly, tracked P. palpebrata did not demonstrate any positive association with sea surface temperatures. During incubating and chick-provisioning periods, tracked P. palpebrata travelled shorter distances to foraging grounds located to the south of breeding islands possibly to maximise returns to chicks while minimising efforts. During nest construction, tracked P. palpebrata travelled to distant foraging grounds to the south of the Antarctic Polar Front in areas of low mesoscale variability suggesting that greater distances can be achieved when they have no chick to feed at the colonies. Individuals of both tracked species foraged within close proximity during energy-demanding periods indicating their ability to employ an efficient foraging strategy that ensures minimal effort whilst maximising returns. Generalised Linear Models with the response variable being species and explanatory variables comprised of sea surface temperatures, annual breeding stages, distance traversed and activity, were conducted to examine the effect of environmental factors on seabird foraging distribution. These models were subjected to robust fitness tests and those that represented ecological reality of the two tracked albatrosses were chosen. The study demonstrates that the most important foraging areas for these two tracked seabird species overlap with the Indian Ocean Tuna Commission Convention area making them vulnerable from incidental capture from high longline fisheries. These results have implications to the conservation of these albatrosses suggesting a need for a multi-faceted approach on fisheries management particularly on mitigation of seabird bycatch in the Indian Ocean Tuna Convention area.

This work examines intra-seasonal rainfall variability over the summer rainfall region of South Africa. Spectral analysis of a precipitation minus evaporation index (P-E) compiled from 16 rainfall stations in the western Transvaal region of South Africa has shown that two dominant spectral peaks occur in the water budget or convection as identified by an outgoing longwave radiation (OLR) index and P-E index. A longer 40-60 day oscillation or Madden Julian Oscillation (MJO) and a shorter 20-30 day ISO are identified. The interaction between the Rossby waves of the mid-latitudes and the MJO of tropics appears to be the main cause of the 20-30 day ISO operating over southern Africa. Hovmoller analysis at 10° S and 40° S has shown that four modes exist in the propagation and oscillatory characteristics of various anomalies. Eastward and westward propagation is noted as well as standing wave patterns and "flip-flop" modes where anomalies alternate between positive and negative across the latitude band with time. The composite analysis revealed a tropically initiated signal of the 20-30 day ISO in the water vapour flux (WVF) anomaly field where strong easterly WVF vectors are noted between the equator and 10°S and between 40° E and 80° E. Strong convergence of water vapour occurs during the wet phase of the 20-30 day ISO over the south-western Indian Ocean and together with strong ridging of the South Atlantic Anticyclone (SAA) causes the south-easterly advection of moisture from the southern Mozambique Channel and over the warm Agulhas Current into South Africa. Post-wet phase anomaly composites do not show much similarity with pre-cursor anomaly composites. This implies that the 20-30 day ISO may be a half cycle of 40-60 days which is consistent with the MJO. However, it is felt that 20-30 day ISO's affecting the southern African region alternate in intensity within the period of the MJO.