Mortalities of wild birds attributed to cyanobacteria have been reported. However, in our previous experimental study Japanese quails daily ingesting environmentally relevant doses of microcystins for 10 and 30 days showed no mortality despite significant biochemical, histopathological and subcellular signs of hepatic damage. It is our hypothesis that under environmental conditions co-exposure to multiple stressors such as for example heavy metals and pathogenic micro-organisms may enhance avian mortality.