Abstract

Whether individuals migrate or not is rapidly shifting in many populations. Exactly how and why environmental change alters migration propensity is not well understood. We conducted a systematic literature review to gain insights into the mechanisms that affect the propensity to migrate. Motivated by findings from our literature review, we constructed density-dependent structured population models to explore the coexistence of migrants and non-migrants, when they coexist, and when they do not. We find that carrying capacity in a seasonal environment determines the dominant type in the population. Partial migration can be maintained, or not, depending on where in the life cycle density-dependent operates. Bet-hedging also promotes partial migration. Our study disentangles density-dependence and density-independence in seasonal environments, providing insights into the coexistence of polymorphism, potentially explaining the rapid change in migration strategy observed.