A REVIEW OF FACTORS AFFECTING PRODUCTIVITY OF BALD EAGLES IN THE GREAT-LAKES REGION - IMPLICATIONS FOR RECOVERY

The bald eagle (Haliaeetus leucocephalus) population in North America declined greatly after World War II due primarily to the eggshell thin ning effects of p,p(')-DDE, a biodegradation product of DDT. After the banning of DDT in the United States and Canada during the early 1970s , the bald eagle population started to increase. However, this populat ion recovery has not been uniform. Eagles nesting along the shorelines of the North American Great Lakes and rivers open to spawning runs of anadromous fishes from the Great Lakes still exhibit impaired reprodu ction. We have explored both ecological and toxicological factors that would limit reproduction of bald eagles in the Great Lakes region. Ba sed on our studies, the most critical factors influencing eagle popula tions are concentrations of environmental toxicants. While there might be some continuing effects of DDE, total PCBs and most importantly 2, 3,7,8-tetrachlorordibenzo-p-dioxin equivalents (TCDD-EQ) in fishes fro m the Great Lakes and rivers open to spawning runs of anadromous fishe s from the Great Lakes currently represent a significant hazard to bal d eagles living along these shorelines or near these rivers and are mo st likely related to the impaired reproduction in bald eagles living t here.