A Lighter Shade of Pink

Thousands of lesser flamingos died from malnutrition last year at Lake Bogoria, Kenya, scientists report.

Researchers are investigating the causes of the recent large-scale mortality of lesser flamingos (Phoeniconaias minor). During the 1990s at least half a million birds died.

Post-mortem examinations on several flamingos found dead at Bogoria in late 2006 revealed that the birds weighed just 63 per cent of their normal body mass. An analysis of the lake water confirmed that very low levels of spirulina--a blue-green bacteria that is the primary food source for lesser flamingos--were leaving the birds with only 10 per cent of their minimum daily food requirements.

"Based on these findings, it appears that starvation needs to be included in the possible causes of flamingo mortality," said David Harper of University of Leicester, principal investigator of Earthwatch Institute Flamingos of the Rift Valley project.

Researchers believe that heavy rains led to swollen seasonal streams, bringing water and high sediment concentrations into the lake that diluted the food supply.

"It is unknown why the birds did not simply leave Bogoria," Harper said. "We speculate that these birds may had arrived at Bogoria already in poor condition and were unable to regain enough strength to move on."

Coincidently, the flamingos observed at Bogoria also tended to be a paler shade of pink, indicating that they were not in good enough condition to breed. Flamingos get their bright breeding coloration from the alpha and beta-carotene in their normal diet. Out of about perhaps 15,000 flamingos, Harper observed less than 100 intensely pink birds.

Behavioral changes in the flamingos were also observed. The birds were not wading or feeding in groups along the shoreline as normal, but instead were dispersed and feeding primarily in the open water. Flamingos were routinely observed feeding from small rain puddles in fields and even in the road, making themselves vulnerable to other causes of mortality.

It's not known whether the strongest mortality factor is natural or caused by humans," Harper said. "We now fear that food stress might lead to large scale flamingo mortality either directly through starvation, or indirectly by increasing susceptibility to infectious diseases or access to toxins."

---LiveScience Staff

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Credit: David Harper