Predation prey games in the evolutionary ecology of migratory species

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Most research on the migration routes, timing of movements, and settlement on breeding or non-breeding grounds of birds and other animals concentrates on relationships with seasonal patterns of food and weather. This research considers the effects of mobile predators on several aspects of migration behaviour of their prey, and vice versa. Both predators and prey should distribute themselves to maximize their reproduction and survivorship, and the two sets of movements interact, in some cases leading to stable patterns. The principle systems where the outcomes of these dynamics are being studied are small sandpipers that breed in the arctic and spend the winter along temperate and tropical coastlines, and their falcon predators. Since the near banning of DDT, falcon populations have steadily increased in North America and Europe, providing a "natural experiment" against which changes in prey behaviour may be assessed. We examine how both falcons and sandpipers have redistributed themselves among wintering sites as the world has become more dangerous for the sandpipers, testing the prediction that more sandpipers will be found at safer, but perhaps more food-poor areas. We also test whether falcons migrate to different latitudes such that more northerly locations are more dangerous for prey than more southerly ones, and how sandpipers with different vulnerabilities, primarily because of differences in body sizes, also migrate to different latitudes.