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

潮间带系统中鸟类的捕食既会对猎物种群产生直接影响，也会对群落的其余部分产生间接影响。同样，许多鸟类依赖潮间带栖息地，其中一些目前受到威胁。为了理解这种依赖，预测栖息地变化的后果，并制定有效的保护策略，我们必须了解水鸟与其生态群落之间相互作用的力量和机制。我建议在芬迪湾的三种潮间带群落类型--泥滩、盐沼和岩石潮间带--研究鸟类的捕食及其相关的间接影响。上湾广阔的泥滩为每年夏天迁徙到该地区的100多万只半裂足沙鼠提供了重要的觅食栖息地，它们以沉积物中发现的泥虾为主要食物。然而，近些年来，泥滩发生了一些变化，琵琶似乎在四处活动，可能是为了寻找合适的食物。我将研究这些鸟是否会吃它们喜欢的猎物以外的东西，并研究这种捕食对整个群落有什么影响。盐沼也被留鸟和候鸟广泛使用。从历史上看，许多沼泽被排干用于农业目的，尽管现在正在努力恢复其中的一些。我建议监测其中一个恢复地点，以研究鸟类对栖息地的利用和沼泽群落组成在恢复过程中如何变化。最后，我建议研究鸟类(主要是鸭子)和岩质潮间带无脊椎动物群落之间的关系。许多迁徙和栖息的海鸭严重依赖这个栖息地。它们的活动有时对它们喜欢的猎物以外的物种产生显著的间接影响，导致系统发生令人惊讶的变化。我将量化这些影响，这将使我们更好地了解控制群落动态的因素，以及系统对潜在干扰或物种丧失的适应能力。从长远来看，所有这些研究的结果将有助于对鸟类如何与潮间带系统中的其他物种相互作用的总体理解。

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.