the sight of millions of beautiful pink lesser flamingos flocking on the lakes of East Africa is breath-taking. But every few years, a mysterious killer wipes out thousands of the birds. Pollution and infectious diseases have for long been fingered as potential causes. But researchers say they have found another culprit.

Geoffrey Codd, a microbiologist at the Scotland-based University of Dundee, and his colleagues claim there is strong evidence that the birds are being poisoned by a naturally occurring toxic cyanobacterium.

It is quite well-known that a lesser flamingo usually feasts on particular species of cyanobacteria called Arthrospira fusiformis . But samples from Kenya's lake Bogoria where 50,000 birds died two years ago, revealed two more species of cyanobacteria