World Waterfowl Populations: Status and Dynamics

Waterfowl comprise some of the most popular and well-studied animals. Their migrations, behavior, breeding biology, and wintering ecology have received considerable attention from scientists, managers, and amateurs alike. From their studies we have gained a better understanding of waterfowl populations and the factors that influence them. Our greater understanding has underscored how much more we have yet to learn. Herein we review the status of waterfowl populations worldwide and examine the critical events that occur during their annual cycle. Many North American duck species are at the lowest numbers recorded. Some northern populations are stable or increasing, a few even to nuisance levels. Other populations, mainly in South America, Africa, and Asia, are poorly known or threatened; some are critically endangered. The most serious threats to these populations are human actions, directly through hunting or indirectly through habitat destruction, pollution, and introduction of predators or competitors. A review of waterfowl population dynamics suggests that, although numbers are influenced by a variety of factors, the success of nesting attempts and the survival of young are of greatest consequence in most populations. Evidence available for ducks suggests that hunting mortality, below a certain threshold, is compensatory; however, in geese the evidence points to it being additive at current population levels. The most critical research needs are information from the tropical and Southern Hemisphere populations, and a better understanding of population processes and the effect of human-induced factors, including habitat alteration and global climate change.