A novel herpesvirus likely indigenous to the magnificent frigatebird (Fregata magnificens) has been linked to episodes of mass mortality of chicks from the Grand Connétable Nature Reserve, a small island in French Guiana. In this colony, around 90% of chicks die each year after showing clinical signs of infection. We hypothesize that these episodes of mass juvenile mortality result from environmental pollutants altering the physiology and parental behaviour of adult frigatebirds.