Partial Migration in a Population of Greater Prairie-Chickens in Northeastern Colorado

Seasonal movements of radio-marked Greater Prairie-Chickens (Tympanuchus cupido) were examined in northeastern Colorado during 1986-1989. Many birds migrated between breeding and winter areas; all appeared to display fidelity to both breeding and winter sites. The average date of migration from winter to breeding areas was 20 February for males and 27 March for females. The average date of migration from breeding to winter areas was 4 July for females and 28 July for males. Much of the variability in timing of migration from breeding areas for females was related to brood status; average date of migration was 10 June for females without broods and 26 August for females with broods. Average migration distance between winter and breeding ranges differed significantly by sex: 9.2 km for females and 2.7 km for males. When migration samples were expanded to include distances between breeding and late summer ranges (as suggested by timing of movements), females migrated an average distance of 10.6 km, while males migrated 2.9 km. Seasonal movements of Greater Prairie-Chickens appear to represent a partial migration with both obligatory and facultative components.