Fri March 5, 2010
Why migratory waterfowl may abandon Ohio River
By Micah Schweitzer
Western Kentucky – Human alterations to the landscape have dried up more than half of US wetlands. Now a new study predicts a warmer climate will also disrupt wetland ecosystems, and ducks will be on the losing end. At a popular stopping point for migratory waterfowl along the Ohio River in western Kentucky, one scientist is noticing changes in migration patterns. Micah Schweitzer reports for the Ohio River Radio Consortium.
Human alterations to the landscape have dried up more than half of U.S. wetlands. Now a new study predicts a warmer climate will also disrupt wetland ecosystems, and ducks will be on the losing end. At a popular stopping point for migratory waterfowl along the Ohio River in western Kentucky, one scientist is noticing changes in migration patterns.
There's a chill in the air on this cloudy 30-degree winter morning, but it's a balmy day for ducks and other migrating waterfowl touching down at the Sloughs Wildlife Management Area near Henderson, Kentucky. Mike Morton is a wildlife biologist with the Kentucky Department of Fish and Wildlife Resources, which oversees the Sloughs.
Mike Morton's team herds ducks into a trap at the Sloughs Wildlife Management Area
Today, he and his team are collecting ducks from a large swim-in water trap. Mike and his team suit up in hip boots and waders and begin herding the ducks toward a narrow chute at one end of the trap. The ducks are loaded into a trailer and taken to be sorted and tagged with a little bracelet around one leg. Of the fifty ducks collected this morning, the vast majority are mallards, notable for their iridescent green heads. Among the minorities are a black duck and a couple of black duck-mallard hybrids.
"That's getting pretty representative. We used to catch about 25% of the ducks we caught in February were black ducks. And we caught four percent today? That's a big change," Morton says.
Habitat loss along the U.S.-Canadian border is putting the less adaptable black duck at a disadvantage to the more dominant mallard.
"Black ducks are kind of a continuing decline," explains Morton, "which is a concern to Kentucky managers, as well as Mississippi Valley managers, as well as to the U.S. Fish and Wildlife Service, because that species appears to be declining in wintering areas all across the state all across the nation."
Morton says much of the black duck's wetland breeding habitat has been cleared, drained, and converted to agricultural fields. He says it's a trend still happening along parts of the Ohio River in Kentucky, Illinois, and Indiana.
Move outside the protected, managed Sloughs area, and he says, "if you drive down any road for any length of time, you're gonna see a track hoe and a bulldozer someplace. And they're cleaning and dredging and clearing and converting bottomland hardwood systems and repairing zones the narrow bands of woody vegetation along stream banks they're clearing them back to where there's nothing left. You're gonna end up with a road, dirt, and agriculture fields."
Already, the U.S. has lost more than 50 percent of its wetlands, and in agriculture-heavy states like Indiana and Illinois, 80 to 90 percent is gone. Paul Doss is a geologist at the University of Southern Indiana. He says agricultural conversion peaked in the late 1980s.
"The most dramatic threat is probably not agricultural conversion. In terms of transformation, it's probably the more urban conversions urban development, urban sprawl, roadway construction, infrastructure building," he says.
Roads and development fragment a single, linked ecosystem. And Doss says the impact on the system as a whole far exceeds the damage to the acreage being developed. He says human intervention is so much faster than natural cycles, nature can't keep up. But human transformation of the landscape is just one challenge to wetlands. A recent study in the journal BioScience predicts a steadily warming climate threatens to dry up remaining prairie wetlands in the northern U.S. and Canada that are home to species like the black duck. While Doss says it's too early to observe global warming's effect on wetlands, Mike Morton says he's seeing bird migration patterns change with the weather. Morton won't say if global warming is the culprit, but he says for the past 10 years, we've been on the mild side of the weather cycle. That means some waterfowl that would have passed through decades ago are spending the whole winter at the Sloughs.
"These birds are migrating south not for their exercise," Morton says. "They're migrating south to get to a latitude where they can make a living for the rest of the winter. And back in the 60s and 70s if you were going to see these wintering conditions, you'd be on the Tennessee-Alabama line or even farther south."
For some birds, mild weather has made life easier. But if temperatures continue to climb and if humans continue to transform the landscape, some species could find themselves without a place to call home.