| Summary: | When resources are spatially and temporally variable, consumers can increase their foraging success by moving to track ephemeral feeding opportunities as these shift across the landscape; the best examples derive from herbivore-plant systems where grazers migrate to capitalize on the seasonal waves of vegetation growth. We evaluated whether analogous processes occur in watersheds supporting spawning Pacific salmon, asking whether seasonal activity of predators and scavengers shift spatial distributions to capitalize on asynchronous spawning among populations of salmon. Both glaucous-winged gulls and coastal brown bears showed distinct shifts in their spatial distributions over the course of the summer, reflecting the shifting distribution of spawning sockeye salmon, which was associated with variation in water temperature among spawning sites. By tracking the spatial and temporal variation in the phenology of their principal prey, consumers substantially extended their foraging opportunity on a superabundant, yet locally ephemeral, resource. Ecosystem based fishery management efforts that seek to balance trade-offs between fisheries and ecosystem processes supported by salmon should therefore assess the importance of life-history variation, particularly in phenological traits, for maintaining important ecosystem functions such as providing marine-derived resources for terrestrial predators and scavengers. Schindler et al. data Observations of bears and gulls taken throughout the Wood River system of SW Alaska. Bear observations are expressed as the total number of years observed per day by camera trap. Gull data are expressed as the total number of gulls observed at sites when surveys occurred.
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