INTRODUCTION

Migration represents one of the most complex and fascinating behaviors in nature. Simply defined, migration is the repeated movement of individuals from one region to another, and can occur over daily, seasonal, and annual time-frames. Migrations can occur over tens of thousand of kilometers, as in the case of the Arctic tern (Sterna paradisaea) moving essentially from pole to pole (Hatch 2002), or it can simply involve movements over distances as small as meters, as is the case of phantom midge larvae (Chaoborus spp.) moving from lake benthos during the day to the open water at night (Roth 1968). Migratory behavior has enormous taxonomic breadth including species of anadromous fish that leave natal rivers to spend several years at sea eventually returning to the same river to spawn and die (Hodgson and Quinn 2002), to the annual migrations of black rat snakes (Elaphe obsoleta) from winter hibernacula to summer breeding and foraging areas (Blouin-Demers and Weatherhead 2002), to the spectacular seasonal movements of long-distance migratory birds between temperate breeding and tropical winter environments (e.g., Keast and Morton 1980; Hagan and Johnston 1992). Movements such as these, by such taxonomically diverse groups of organisms, define migratory behavior and motivate the need to understand how these movements interact with and are modified by the physical structure of their environment.

For the majority of migratory birds, the spatial areas traveled are vast and the individuals too difficult to follow throughout the annual cycle.