Water Lettuce on Lake Onalaska: Thursday November 12 Date: 11/12/2015 07:24 AM From: Fritz To: Participating Natural Resource Agencies and Volunteers A few water lettuce plants were found on each of two surveys of the lower Brice Prairie Channel in the last 5 days, so there are still some out there - 4 plants on Nov 7 and 1 plant on Nov 11. Composite map attached. Very strong NW (offshore) winds are forecast for today (Nov 12) but there shouldn't be any invasive plants to broadcast from the lower Brice Prairie Channel. If you're looking along the Lake Onalaska shoreline these days you will likely see quite a few dead duck carcasses....the result of yet another invasive species, the faucet snail. This small exotic snail brought with it a trematode (parasitic flatworm) that is very often fatal to ducks that eat the snails. In some years it has been estimated that 5,000 waterfowl have succumbed to the trematode disease on Lake Onalaska, mostly lesser scaup ("bluebills") and American coot. The first waterfowl mortalities from trematodiasis were documented in 2002. You can't miss the huge numbers of bald eagles that are attracted like a magnet to the infected, weakened waterfowl. I am routinely counting over 50 eagles in the trees on Cormorant Island alone and the former USFWS aerial surveys have documented up to 500 eagles on the lake this time of year. The trematodes do NOT affect the eagles (or humans or anything else that consumes the infected ducks) - the disease is only acquired by eating infected snails directly. If you look out on the lake you will see the eagles swooping low and "hazing" flocks of ducks, looking for weakened birds that do not fly or swim well. A healthy duck is a challenging prey for the eagles, but the disease-weakened birds are....well, sitting ducks. Ducks are almost too heavy for eagles to carry off. You'll often see the eagles struggling and sometimes dropping their prey several times before they can get them to the shore where they can eat them, leaving shredded feathers and bony duck parts all over the shorelines this time of year. American coot: https://www.allaboutbirds.org/guide/American_Coot/id Lesser scaup: http://www.audubon.org/field-guide/bird/lesser-scaup Faucet snails and waterfowl die-offs: http://pubs.usgs.gov/of/2007/1065/pdf/ofr_20071065.pdf --Fritz Funk Event Summary on Lake District Web Page: http://www.lakeonalaska.org/invasive_species.html attachement: Nov7_11.jpg