Can nest predation and predator type explain variation in dispersal of adult birds during the breeding season?

Abstract

Many types of predators depredate bird nests and thus potentially influence the spatial distribution of their prey. We used a simulation model of a double-brooded songbird's nesting season to test three predictions about the selective advantage of dispersing different distances after nest predation by predators with varying home range sizes. Our results supported the predictions that (1) dispersing birds had higher success than nondispersing birds after predation of the first nest, (2) dispersing beyond the home range of the nest predator increased the success of the second nest, and (3) birds whose first nests were depredated early in the nesting cycle did better by dispersing farther than birds whose nests were depredated later in the nesting cycle. Our results provide evidence that predation and predator characteristics may cause variation in adult dispersal distances during the breeding season. However, we did not find an advantage for long-distance dispersal when predators with small- or medium-sized home ranges were responsible for the predation event. The critical decisions of dispersal and dispersal distance made by adult birds are complex, but our model demonstrates that predation events can create a selective advantage to disperse.