The Development of Bird Migration Theory

Abstract

The full magnitude and complexity of bird migration have not been possible to grasp until after the revolutionary discoveries made with the aid of, e.g., ringing, systematic field observations and radar. These have opened up opportunities for a more formalized theoretical construction work during the recent decades. The introduction of theoretical concepts and tools from flight mechanics into the field of bird flight and migration took place during the 1960s and 1970s and paved the way for the use of optimization analysis to evaluate adaptive aspects of flight behaviour, fuel deposition and responses to wind drift by migrating birds. The approach has been expanded, i.e. through the use of stochastic dynamic programming, to analyse the expected disposition of the migratory journey (with respect to Eight and stopover arrangement) under different ecological conditions and the adaptive temporal structure of the annual cycle of a migratory bird. Theoretical considerations also play an important role in analysing the orientation of migratory birds, their population ecology, and patterns of differential migration. Theoretical developments in these areas are reviewed. In the long run evolutionary and mechanistic theories must meet and join to provide a full understanding. While optimization models standing up to critical tests may help to identify primary forces of balancing selection and constraints, mechanistic theories are needed to tell us how the inherent biological algorithms operate within the sensory, neural and physiological systems to control behaviour and design in an adaptive way.