Environmental mercury — much of which comes from human-generated emissions — is impacting both the health and reproductive success of common loons in the Northeastern US. Loons with high levels of mercury — about 16 percent of the adult population in the study area — were found to spend some 14 percent less time at the nest than normally behaving birds. Unattended nests have a higher rate of failure due to either chilling of the eggs or predation by minks, otters, raccoons and other egg robbers.