The Role of Migration and Winter Mortality in the Life History of a Temperate-zone Migrant, the Dark-eyed Junco, as Determined from Demographic Analyses of Winter Populations

ABSTRCT.--Thisstudy of migratory Dark-eyed Juncos (Junco h.hyemalis) investigates differences in winter population structure and dynamics associated with north-south variation in wintering site and considers the relationships between these winter differences and population dynamics at other seasons.Banded juncos were captured and recaptured in several winters at four latitudes (42-33.5),and results were integrated with long-term United States Fish and Wildlife Service records of recoveries throughout the winter range.The data suggest: (1) Populations wintering in the north experience higher winter mortality than populations wintering in the south.(2) Sex and age do not affect the probability of overwinter…