Influence of salmon on the nesting ecology of American dippers in Southeastern Alaska

Salmon runs influence the ecology of several mammalian species in Southeast Alaska, but little is known about the effect of salmon runs on avian predators. We tested the prediction that reproductive performance of American dippers (Cinclus mexicanus) nesting along stream reaches that have seasonal populations of spawning salmon is higher than that of those nesting along stream reaches without salmon runs. Dippers on reaches with salmon near Juneau, Alaska, had heavier fledglings and less brood reduction than dippers on reaches without salmon. Higher fledgling mass and less brood reduction were associated with the occurrence and nutritional value of young salmon in the nestling diet and not with aquatic macroinvertebrate abundance (which decreased during the salmon spawning period).