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G.2-1: Nonbreeding distribution dynamics of waterfowl: Are patterns changing in the 21st Century?

Presented by Tom Moorman - Email: tmoorman@ducks.org

Most waterfowl species in North America are highly migratory, an adaption arising ultimately from pressures exerted by a seasonal climate resulting from annual changes in the tilt of the earths axis relative to latitude. Migration enables waterfowl to exploit spatially and temporally variable and highly heterogenous landscapes at large geographic scales.. While migratory behavior in birds is stimulated by annual changes in photoperiod, on an annual or seasonal basis, proximate factors interact to influence the timing, duration, and distance of migratory movements that ultimately shape the nonbreeding distribution of birds across the continent. Paramount among these proximate influences are weather, habitat quantity and quality, and disturbance. Enduring shifts or expansions in winter distribution are well documented for some species of waterfowl (e.g., Canada geese, greater white-fronted geese, snow geese), likely driven by the interacting effects of a warming climate, landscape-scale changes in habitat resources, and changing anthropogenic pressures (e.g., harvest). Evidence for long-term distributional shifts of other species is emerging at multiple scales and across continents, further exemplifying the remarkable adaptability of waterfowl to an ever-changing environment, but potentially also influenced by poorly understood differential demographics among populations or subpopulations. Long-term changes and interannual dynamics of nonbreeding waterfowl, with causes over which we have limited to no management control, have important consequences for North American Waterfowl Management Plan habitat, harvest and people objectives. Hence, a thorough understanding of long-term change and interannual variability in nonbreeding waterfowl distribution is central to the waterfowl conservation enterprise in North America. We examine known and probable changes in distribution of nonbreeding waterfowl, potential implications for the waterfowl conservation enterprise, and call for increased collaboration to address key uncertainties around these issues.
Session: Migration & Winter Distribution Changes (Thursday, August 29, 10:30 to 12:00)