David J. Cliplef J. Christian Franson 1992 <p>Summarized are necropsy results from 222 carcasses of Common Loons (<i>Gavia immer</i>) submitted to the National Wildlife Health Research Center from 1976 through 1991. &nbsp;The carcasses were from 18 states, and 10 or more birds each were from Minnesota, Florida, Virginia, Michigan, Wisconsin, Maine, and North Carolina. &nbsp;Seventy-three (33%) carcasses were emaciated, and in some of these birds emaciation was thought to be related to exposure to mercury. &nbsp;OVer 40% of these emaciated birds were from Florida. &nbsp;Trauma, including blunt trauma of unknown origin, outboard motor propeller wounds, and shooting caused the deaths of 49 (22%) loons, 30 of which were from Minnesota. &nbsp;Diseases, primarily avian botulism type E and aspergillosis, account for 39 (18%) moralities and lead poisoning for 14 (6%), 11 of which had fishing sinkers in their stomachs. &nbsp;Most of the avian botulism type E cases occurred during two outbreaks on Lake Michigan. &nbsp;Seven of the 14 lead-poisoned birds were from Minnesota. &nbsp;Nine (4%) birds died of miscellaneous causes and 9 (4%) of drowning, primarily from entanglement in nets. &nbsp;No diagnosis could be reached for 29 (13%) carcasses. &nbsp;Sample bias precludes interpretation of these data to represent actual proportional causes of mortality in the loon population. &nbsp;However, the sample size is sufficient to clearly identify major causes of mortality.</p> application/pdf en U.S. Fish and Wildlife Service Causes of mortality in common loons text