Continuity and advancement of Trumpeter Swan Cygnus buccinator and Tundra Swan C. columbianus population monitoring in Alaska

Abstract

In Alaska, four extensive censuses of Trumpeter Swans by the U.S. Fish and Wildlife Service have documented an exponential growth of the summering population since 1968 (white (>l year-old) swans: 1968-1,924, 1975-2,993, 1980-5,259,1985-7,773). A sampling design based on the census results using stratified random plots estimated 7,145±660 white Trumpeter Swans in 1986. Annual line transect surveys over most of the Alaska nesting range, except for the North Slope, have documented an increasing breeding population of Tundra Swans 1965-1989. A modified sampling technique, similar to the one for Trumpeter Swans, but employing smaller sized plots, has been used successfully in parts of Alaska to better estimate subpopulations of Tundra Swans. Expanded sample surveys for both species on the summering grounds are recommended for North America. Enhanced management of both species, as well as for other less visible waterfowl, is envisioned with full implementation.