From the "prairie potholes" of Canada and the upper Midwest to the destination states of Arkansas and Louisiana, the rhythms of the cross-continental migratory bird route known as the Mississippi Flyway are changing. In Missouri, where the average winter temperature has been rising, hunters say birds are arriving later and sticking around longer before bolting for warmer redoubts. Elsewhere, wetlands are not freezing over the way they once did. As hunters point their shotguns toward the sky and fire, a question echoes in the spent powder: what is up with the ducks? Five-year averages for "duck use" days on some conservation areas in Missouri show peaks that come a week or more later in the year than do the 30-year averages. In Missouri, the average winter temperature this decade has been about 35 degrees, roughly 2 degrees higher than the previous peak around 1930. "We're having milder falls, later winters," said Dave Erickson, chief of the wildlife division for the Missouri Department of Conservation. "What we don't know is if the trend that affects migration and the hunters' desire for a longer hunting season is a temporary fixture or a permanent fixture." Sure science is elusive. Scientists and state wildlife officials say there is not clear-cut data to support the reports of changes in duck behavior, but the patterns are familiar. They note that various other animal species, including songbirds, frogs and foxes, are developing different patterns for breeding and migration. "We're seeing northern range shifts of lots of birds and butterflies," said Camille Parmesan, a professor of conservation biology at the University of Texas and a member of the United Nations panel that was awarded the Nobel Peace Prize for its work documenting climate change. Many hunters, wildlife officials and scientists say the changes have added new mystery to waterfowl migration and to how to manage it.
The New York Times
In Duck Blinds, Visions of Global Warming