Priority Access to Food in Migratory Birds: Age, Sex and Motivational Asymmetries

Abstract

Although many landbird migrants are capable of making spectacular, nonstop flights over ecological barriers, including the Sahara Desert, the eastern Atlantic Ocean, and the Gulf of Mexico, few actually engage in nonstop flights between points of origin and destination. Rather, they stop over periodically, sometimes for only a few hours and other times for a few days, before resuming migratory flights. When a migrating bird stops during passage, she almost invariably finds herself in unfamiliar surroundings at a time when energy demands are likely to be high, often faced with conflicting demands between predator avoidance and food acquisition, competition with other migrants and resident birds for limited resources, unfavorable weather, not to mention the possible need to resolve orientation errors (Moore et al. 1995). How well she solves those problems will determine the success of her migration, while a successful migration is ultimately measured in terms of her survival and reproductive success.