Preface.

The article introduces the November 2003 issue of the journal "Oikos." The paper in this issue are contributions to a symposium held at the Department of Animal Ecology, Lund University, February 21-24, 2002. It says that study and analysis of migration are important elements of evolutionary ecological research. Current immigration research is dynamic as manifested by an expanding theoretical fundament based on locomotion mechanics, transport ecology and optimality theory, along with a growing body of experimental evidence abut the animals' orientation mechanisms, physiological adaptations and the genetic regulation of different migratory traits. The aim of the symposium was to evaluate the current interplay between theoretical considerations of time and energy factors in migration and the overall migration performance in time and space as recorded under natural conditions in the field.