Trumpeter Swan Survey of the Rocky Mountain Population, Fall 2002

摘要

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.