Variation in migration strategies of North American sea ducks

Migration exerts strong effects on population dynamics, so consideration of migration as a driver of population change is an important area of inquiry. Sea ducks (Mergini) exemplify the wide range in types of migration strategies, which become more variable with the addition of a third migration to distinct molting areas. We discuss the three migrations, summer, fall, and molt, and emphasize similarities and differences within and among species. For each migration, we focus on timing, routes and stopover sites, nutrient reserve acquisition, stopover behavior, flight behavior, interannual constancy at stopover sites, and variation among sexes and ages. Last, we describe individual variation of annual flight paths, discuss inter- and intra-annual fidelity at stopover sites, examine the role of the environment on migration paths, and evaluate variability and limitations of speed and duration of migration.