ANIMAL MIGRATION AS A MOVING TARGET FOR CONSERVATION: INTRA-SPECIES VARIATION AND RESPONSES TO ENVIRONMENTAL CHANGE, AS ILLUSTRATED IN A SOMETIMES MIGRATORY SONGBIRD.

Identifying important "migratory species" and the characteristics of their migrations might sound like a simple starting point for efforts to conserve and protect animal migrations. However, migrations are dynamic phenomena that vary over space and time, and migratory behaviors can vary substantially among closely related species, subspecies, races, or populations, and even among individual animals within a single population. The migratory behaviors of populations or individuals can also change rapidly-or be lost entirely-in response to habitat alteration or climate change. These complexities present both challenges and opportunities for initiatives to conserve animal migrations. In this Article, we discuss the concepts of intra-species variation in migration and the sensitivity of migrations to environmental change, and we consider the implications of these topics for legal, policy, management, and research agendas.