The ecology of East African soda lakes: implications for lesser flamingo (Phoeniconaias minor) feeding behaviours

This thesis investigates the feeding ecology of the lesser flamingo (Phoeniconaias minor). Studies took place at six endorheic alkaline-saline lakes within the East African Rift Valley, which varied in terms of taxonomic composition and biomass, both spatially and temporally. The lakes could be categorised as Arthrospira fusiformis dominated (lakes Bogoria and Sonachi), diatom dominated (Lakes Natron and Elementaita) or ‘other’ cyanobacteria dominated (lakes Oloidien and Nakuru). From 2009 to 2013, the lake levels were consistently rising with the average biomass reducing concurrently; maximum surface A. fusiformis recorded was > 800 mg L-1 in 2009 at Lake Bogoria, falling to < 50 mg L-1 in 2013. A reduction in average biomass was recorded at all lakes throughout the study period, with the exception of Lake Natron, where higher diatom abundance was recorded in 2011 than in 2009. This study identified 10 distinct feeding behaviours utilised by lesser flamingos at different times of day. Different behaviours were also employed to access different food resources from a variety of niches throughout the aquatic habitat: from the lake’s edge, the open water and the lake-sediment interface. Deep water feeding was occurring in higher frequency than recorded previously, at Lake Bogoria where flamingos were exploiting a highly concentrated food resource of sedimented A. fusiformis, discovered during this study. This confirms that deep water feeding behaviours are more common than only being utilised to access diatoms as an emergency food source, as has been suggested. The time spent feeding was negatively correlated with food abundance across the six lakes with lower biomass requiring longer feeding duration, however, at Lake Bogoria a positive correlation was identified, suggesting re-stocking of energy reserves. A positive correlation was identified between the distribution of food resources within Lake Bogoria and lesser flamingo distribution across the lake. Finally, a significant difference was found between flock density when feeding on different food sources (more densely flocked when feeding on A. fusiformis than on diatoms) or through different feeding behaviours.