Predation by aquatic birds in intertidal systems: effects on community structure and implications for habitat conservation

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Predation by birds in intertidal systems can result in both direct effects on prey populations and indirect effects on the rest of the community. Similarly, many birds depend on intertidal habitat, some of which is currently threatened. To understand this dependence, predict consequences of habitat change, and develop effective conservation strategies it is critical that we understand the strength and mechanisms of interactions between aquatic birds and their ecological communities. I propose to study bird predation and associated indirect effects in three intertidal community types - mudflats, saltmarshes, and rocky intertidal areas - in the Bay of Fundy. Extensive mudflats in the upper Bay provide important foraging habitat for more than 1 million Semipalmated Sandpipers that migrate through the area each summer, feeding heavily on mudshrimp found in the sediment. However, mudflats have changed somewhat in recent years, and sandpipers appear to be moving around, perhaps in search of suitable food. I will examine whether these birds do eat things other than their preferred prey, and study what effect this predation has on the entire community. Saltmarshes are also used extensively by both resident and migratory birds. Historically, many marshes were drained for agricultural purposes, though efforts are now underway to restore some of them. I propose to monitor one of these restoration sites to examine how habitat use by birds and marsh community composition changes as recovery proceeds. Finally, I propose to examine the relationship between birds (primarily ducks) and a rocky intertidal invertebrate community. Many migrating and resident sea ducks rely heavily on this habitat. Their activities sometimes have significant indirect effects on species other than their preferred prey, resulting in surprising changes in the system. I will quantify these effects, which will provide us with a better understanding of the factors that control community dynamics and the resilience of the system to potential disturbance or loss of species. In the long term, results of all these studies will contribute to a general understanding of how birds interact with other species in intertidal systems.