Trumpeter Swan Survey of the Rocky Mountain Population

The Rocky Mountain Population (RMP) of trumpeter swans (Cygnus buccinator) consists of birds that nest primarily from western Canada southward to Nevada and Wyoming. The population is comprised of several flocks that nest in different portions of the overall range. The RMP/Canadian Flocks consist of birds that summer primarily in southeastern Yukon Territory, southwestern Northwest Territories, northeastern British Columbia, Alberta, and western Saskatchewan. The Tri-state Area Flocks summer in areas at the juncture of the boundaries of Montana, Wyoming, and Idaho (hereafter termed the tri-state area) and nearby areas. The RMP/Canadian and Tri-state Area flocks winter sympatrically primarily in the tri-state area. In addition, efforts have been made to establish several restoration flocks, such as those at Ruby Lake National Wildlife Refuge (NWR) in Nevada (i.e., Nevada flock) and those at Malheur NWR and Summer Lake Wildlife Management Area (WMA) and vicinity (i.e., Oregon flock), by translocating adult swans and cygnets from other portions of the RMP. These birds tend to winter in areas near those where they nest. This report contains information only from the Tri-state Area and restoration flocks, collectively referred to as the RMP/U. S. Breeding Segment. These terms for the various groups of swans are consistent with the RMP Trumpeter Swan Implementation Plan (Pacific Flyway Study Committee 2002). The Fall Trumpeter Swan Survey is conducted annually in September. The survey is conducted cooperatively by several administrative entities and is intended to provide an accurate count of the number of RMP trumpeter swans that summer in the U. S. The history of the survey dates back to the 1930s, although methods and survey coverage have changed over time as the number of swans increased and new technologies became available. Survey methodology and coverage have remained fairly consistent since 1966 (D. Olson, pers. comm.). To be consistent with previous reports, only the data from 1967 to present were analyzed for this report. The data are used by managers to assess the annual status of the Tri-state Area Flocks and restoration flocks. Observers counted 371 swans (white birds and cygnets) in the U. S. Breeding Segment of the Rocky Mountain Population of trumpeter swans during fall of 2002, a decrease from 475 counted from comparable areas last year and the lowest count since 1993. The number of white birds (311) declined 23% from that of last year, while the number of cygnets (60) decreased by 15%. Declines occurred in all 3 states in which the Tri-state Area Flocks nest, and was greatest in Montana (-37%). Decreases in Idaho and Wyoming were 20% and 8%, respectively. The number of birds in restoration flocks also decreased 17% compared to the count from last year. The count for the Tri-state Area Flocks this year was a marked departure from their recent upward trend in numbers. The tri-state area continues to experience drought conditions, with Palmer Drought Index values the lowest recorded since surveys were initiated in the 1930s.