PREDATION DANGER IN THE ECOLOGY OF MIGRATION

点击翻译按钮获取中文摘要

PREDATION DANGER IN THE ECOLOGY OF MIGRATION******Top predators exert powerful effects on prey populations. As exemplified by the changes induced in the Yellowstone ecosystem by the reintroduction of wolves, these effects can ripple throughout entire communities, transmitted via the anti-predator behavior of prey animals. The strong recovery of raptor populations since 1973 (when DDT was banned) is a continental scale version of the Yellowstone wolf reintroduction, and suggests that analogous impacts are to be expected. In recent NSERC DGs, I found that top predators (falcons of the genus Falco) strongly impact the ecology and evolution of migration in sandpipers of the genus Calidris. The projects I propose here continue this line of inquiry, asking whether anti-predator behavior plays a role in other aspects of their biology linked to migration. ******Like many other avian migrants, the western sandpiper (Calidris mauri) shows strong nonbreeding sexual segregation. Does predation risk affect dispersion over non-breeding areas? I propose to test the `predation risk' hypothesis, originally put forward for ungulates. The hypothesis predicts that members of the more vulnerable sex pay a cost (greater distance) to migrate to safer nonbreeding sites. ******The aspect ratio (width/length) of wings greatly affects flight performance, with long wings better for energetic efficiency, and wide wings better for rapid take-off and agility, traits important in eluding predators. Data show that the wing length of semipalmated sandpipers (Calidris pusilla) has shortened dramatically since 1980. I propose to test the hypothesis that natural selection for more defensive flight morphology, created as falcon populations recovered, is responsible for this morphological shift.******The study of population dynamics has of course considered predation, but the role of anti-predator behavior has received little attention. I have found that the population dynamics of nonbreeding dunlins (Calidris alpina) has not been affected by falcons over the past 36 years, even though falcon numbers have increased 3-7 fold. I propose to test the hypothesis that a shift by dunlins toward more defensive non-breeding behavior (analogous to the wing length shift above) has mediated the effects of predators and starvation in a compensatory fashion.******Finally, I propose to continue my work on sockeye salmon Oncoryhnchus nerka. The role of predation danger in the ecology and evolution of salmon migration has rarely been considered. In British Columbia, sockeye populations differ greatly in the timing of their up-river spawning migrations, a pattern classically explained by the effects of temperature on adult and incubation metabolism. I propose to test the hypothesis that river-entry timing is selected for to avoid exposure to predators such as bears. **