The importance of stopover habitat for developing effective conservation strategies for migratory animals

Abstract

Although stopover habitats are used by many species as refuelling stations during migration and can be critical for survival and successful reproduction, they are rarely incorporated in year-round population models and conservation strategies. We incorporate stopover habitat into a density-dependent population model and then use this model to examine how optimizing one-time land purchase strategies for a migratory population is influenced by variation in the quality and the strength of density-dependence in a stopover habitat used for both fall and spring migration. As the strength of the density-dependence in the stopover habitat increases, the optimal amount of stopover habitat purchased increases while the amount of habitat during the stationary periods of the annual cycle (breeding and wintering) decreases. Any change in the cost of purchasing stopover habitat affects investment strategies in all three periods of the annual cycle. When the quality of the stopover habitat is high, the optimal strategy is to invest in low-quality habitat during breeding and wintering and when the stopover habitat quality is low, the optimal strategy switches to investing in high-quality habitat during the stationary periods. We apply this model to a threatened warbler population and demonstrate how purchase decisions to conserve stopover habitat that are not coordinated with conservation actions on the breeding and wintering grounds can potentially result in a lower population carrying-capacity compared to considering habitat in all three periods of the annual cycle simultaneously. Our model provides potential guidelines for developing conservation strategies for animals that rely on refueling habitats between the stationary breeding and non-breeding periods of the migratory cycle.