Causes of mortality in Trumpeter Swans Cygnus buccinator in Minnesota 1986-89

L A Degernes, R K Frank


Between January 1986 and June 1989, 116 Trumpeter Swans were presented to The Raptor Center at the University of Minnesota U.S.A. for post mortem examination to determine the cause of death. In all cases a thorough gross post mortem examination was conducted with histopathology and microbiology included in selected cases. Liver lead analysis was conducted in nearly every case, even when the cause of death was known. Lead poisoning as a result of the ingestion of spent lead shotgun pellets was the major cause of death (53 birds, 45.7%). Aspergillosis, a fungal respiratory disease, accounted for 18 deaths (15.5%). Traumatic injuries such as shooting or power lines resulted in 13 deaths (11.2%). A variety of miscellaneous diseases caused another 13 deaths (11.2%). Ten birds (8.6%) died of, or were euthanized for developmental or congenital diseases. The cause of death could not be determined for nine birds (7.8%).

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