Demography of eastern population tundra swans, Cygnus columbianus columbianus

Abstract

We present rates o f productivity and survivorship during thefirstyear o f lifefor Eastern Population Tundra Swans based on several extensive data sets. Our main objective is to illustrate how such data can be used to construct a life table fo r populations that are inaccessible except by aerial survey on the breeding grounds or that migrate long distances and disperse over wide areas, and thus that are difficult to study via intensive long-term investigations. Our data were obtained from the northwestern third o f the breeding range ofEastern Population Tundra Swans and throughout their wintering range during 1967-1989. An average o f 77% o f the sampled birds apparently held territories in the spring, 34 % o f them nested successfully, and the number o f young per successful nest was 2.46. Survivorship during the first migration averaged 52% and during the first winter averaged 76%. We identify the additional information needed to construct a life table from these estimates and discuss problems encountered in using extensive survey data fo r these purposes.