Parasite Killing Thousands of Migrating Ducks

Biologists in upper Minnesota say a parasite carried by an exotic snail species is responsible for killing thousands of ducks in just the past ten days, and they fear many more waterfowl could perish when the migration kicks into high gear as the weather chills up North.

My friend and associate Chris Niskanen, outdoors editor for the St. Paul Pioneer-Press, alerted me to the news of duck deaths in an email this morning. It’s news that’s sure to get the attention of waterfowlers along the Mississippi flyway.

Niskanen writes that Minnesota DNR biologists believe at least 3,000 lesser scaup (bluebills) have died on Lake Winnibigoshish since Oct. 28 after ingesting non-native snails that are hosts to deadly parasites known as trematodes.

The DNR reports that hundreds of coots also have died in the past week. Scaup, like coots, are divers that often feed on snails and other mollusks below the water’s surface.

Biologists are understandably concerned that more migrating—and hungry– bluebills stopping over at the 58,500-acre lake may also succumb to the deadly parasite.

Trematodes attack the ducks’ lower intestines and feed on their blood. One dead duck tested last week contained 7,000 trematodes–seven times the number that is usually fatal.

Steve Cordts, DNR waterfowl specialist, told the Pioneer-Press reporter the extremely high level of parasites is proving lethal to the ducks in one to two days, rather than three to eight days with fewer numbers.

Cordts said the tiny parasites are responsible for the deaths of an estimated 25,000 ducks in Minnesota since 2002, primarily bluebills and coots on the Mississippi River near Winona.

The unfortunate waterfowl deaths are the direct result of yet another invasive species that was unwittingly introduced into a non-native environment. It is thought that the snails, which are popular for home aquariums, gained a foothold in Lake Winnibigoshish after someone illegally released a few there.