Riding the crimson tide: mobile terrestrial consumers track phenological variation in spawning of an anadromous fish

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 opportun...