Subcommittee on Rocky Mountain Trumpeter Swans, 2012. Pacific Flyway management plan for the Rocky Mountain Population of Trumpeter Swans, Pacific Flyway Study Committee, [c/o USFWS, DMBM], Portland, Oregon. Unpublished report.
Trumpeter swans (Cygnus buccinator) are native only to North America. Although no historical estimates of their abundance are available, by 1900 they had been eliminated from most of their historical range in the U.S. and Canada. Through habitat conservation, protection from illegal shooting, supplemental winter feeding, and re-introduction and translocation efforts, trumpeter swans have increased from a few hundred birds to nearly 35,000. To facilitate monitoring and management, the U.S. Fish and Wildlife Service (FWS) and Canadian Wildlife Service (CWS) designated three populations: the Pacific Coast (PCP), the Rocky Mountain (RMP), and Interior (IP). The Rocky Mountain Population (RMP) increased from less than 200 in the early 1930s to 4,701 in February 2007. Even though distribution patterns have changed since the late 1980s, about 80% of the population (n=4,449/5,484 in winter 2006) continues to winter in the core Tri-state Area of southeast Idaho, southwest Montana, and northwest Wyoming. This restricted winter range distribution is still a priority concern for the RMP, although there has been a gradual shift to the southern half of the core tri-state area and sites further south since hazing and winter translocations began at Harriman State Park (HSP) and Red Rock Lakes National Wildlife Refuge (NWR) in 1990 (Shea and Drewien 1999). Coincident with summer releases of captive-raised swans in Wyoming (1994-2002) and at Bear Lake in Idaho (2001-2004), and winter translocations in Idaho (2001-2004), an increasing percentage of swans have wintered south of the core Tri-state Area in the Green, Salt, and Bear River drainages of Idaho and Wyoming. In the winter of 2007, 34% (n=351/1,024) of swans in Wyoming and 23% in Idaho (n=696/3,080) were south of the core area (data from U.S. Fish and Wildlife Service 2007). A small number of swans have been reported from Utah, Colorado, Nevada, Arizona, and California as well.