Ecological Trap

After a severe drought gripped the Prairie Pothole region of the United States and Canada in the 1980s, populations of almost all dabbling duck species that breed there have recovered. But not northern pintails. Now, a new study by a team of researchers suggests why: they have been caught in an ecological trap.

The Prairie Pothole region straddles the U.S.-Canada border and sprawls from central Iowa in the south to Alberta in the north, covering a large swath of Minnesota, South Dakota, North Dakota, Manitoba, and Saskatchewan in between.

Image by U.S. Fish And Wildlife Service

"With increasing cropland cover in the region, pintails have been selecting cropland over scarce alternative nesting habitat, probably because it is similar to the native mixed-grass prairie they evolved to nest in," said lead researcher Frances Buderman, assistant professor of quantitative wildlife ecology in the college. "That behavior results in fewer pintails the following year due to nest failures from predation and agricultural practices."

The U.S. Fish and Wildlife Service's North American Waterfowl Management Plan calls for more than four million pintails, but recent estimates are only half of that. The reason pintails are not thriving like other dabbling ducks, according to Buderman, is that they are being "misled" by modern cropping methods and climate change into choosing risky nesting habitat.

To reach their conclusions, which were published in the Journal of Animal Ecology, the researchers used more than 60 years of data from the U.S. Fish and Wildlife Service and the Canadian Wildlife Service, which have monitored spring population sizes for North American waterfowl since 1955.

--Jeff Mulhollem