Contributions of endocrinology to the migration life history of birds

• Migration is a complex life history stage common to thousands of species of bird.
• It involves impressive phenotypic plasticity and is composed of distinct phases.
• Phases include: development, mature expression (fueling, departure, flight) and arrival.
• Endocrine contributions to the regulation and expression of these phases are described.

Migration is a key life cycle stage in nearly 2000 species of birds and is a greatly appreciated phenomenon in both cultural and academic arenas. Despite a long research tradition concerning many aspects of migration, investigations of hormonal contributions to migratory physiology and behavior are more limited and represent a comparatively young research field. We review advances in our understanding of the hormonal mechanisms of migration with particular emphasis on the sub-stages of the migration life history: development, departure, flight and arrival. These sub-stages vary widely in their behavioral, ecological and physiological contexts and, as such, should be given appropriate individual consideration.