Once an abundant and conspicuous presence in wetlands across much of north-central North America, Trumpeter Swan (Cygnus buccinator) poplulations were decimated in the mid- to late 1800s by a combination of market hunting, subsistence hunting, and habitat loss. Since then, restoration has focused primarily on reintroduction efforts in which captive-reared birds are released and then monitored. From 1991 to 1993, 44 birds were released into Seney National Wildlife Refuge (Schoolcraft County, Michigan) in a multi-agency attempt to enhance the breeding population of this species in the Upper Great Lakes region. To provide information useful to swan restoration efforts elsewhere, this paper summarizes 14 years of Trumpeter Swan occupancy and productivity at Seney. In doing so, we document the first substantial inter-annual decline in swans on the Refuge and provide evidence that suggests birds may now be dispersing onto other lakes and wetlands in the eastern Upper Peninsula of Michigan. We also present information from which we infer processes regulating swan numbers and rates of productivity and discuss both the continued need for monitoring and the need for research to examine the effects swans might have on other components of aquatic ecosystems at the Refuge.
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Vol. 29 • No. 1