The effect of spawning salmon subsidies on reproduction and territoriality of an avian insectivore

Resource subsidies link marine, freshwater and terrestrial ecosystems. The movement of marine-derived nutrients from spawning salmon into riparian forests through multiple trophic pathways provides an important subsidy to recipient terrestrial ecosystems. Studies have established links between salmon subsidies and higher densities of indirect consumers, such as insectivorous birds. However, the mechanisms supporting these higher densities remain largely unexamined as studies have focused on patterns rather than processes. This thesis examines the mechanisms and trade-offs supporting higher densities of Pacific wrens (Troglodytes pacificus), a species of avian insectivore, along salmon streams. I found that salmon subsidies mediate habitat selection and reduce territory sizes of adult male wrens along riparian forests. I then examine the effect of salmon subsidies on reproductive success and effort. Thus, not only do salmon subsidies shape spatial occurrence of adult wrens, they also impact breeding behaviour and effort, leading to higher wren reproductive success on salmon streams.