March 29, 2005 POOR WATER QUALITY IN IOWA WETLANDS MAY THREATEN MIGRATING WATERFOWL By Lowell Washburn Iowa Department of Natural Resources KEOKUK---This year's spring migration has gathered a full head of steam. Hundreds of thousands of waterfowl are currently winging their way northward across Iowa. Twenty years ago, the lesser scaup was one of our most common spring visitors. Recently, however, scaup populations have continued to show an alarming, downhill slide. The total number of breeding scaup [also referred to as bluebills] has declined from more than 6 million birds during the 1970's, to an average of just under 4 million during the past ten years. No one can say for sure why these popular waterfowl are on the wane. But ongoing investigations are beginning to point a finger at declining water quality values in Iowa wetlands. "What we do know is that when migrating scaup arrive at Keokuk [on Pool 19 of the upper Mississippi River] their body weights are at or above historic levels. Ironically, when those same ducks arrive in northern Minnesota, they have a substantially lower body weight than when they arrived there during the mid-1980s," says Iowa DNR Waterfowl Biologist, Guy Zenner. For reasons not totally understood, migrating scaup are losing critical body reserves as they migrate across Iowa. Those reserves, say scientists, are a critical requirement for successful reproduction. Those declining body weights, says Zenner, are resulting in later nesting dates, reduced [egg] clutch size, and reduced survival of adult females. Scientists from Louisiana to Canada are currently investigating the ongoing dilemma. In addition to looking at the body condition of individual ducks, wildlife biologists are also taking a serious look at the overall health of the wetlands, migrating scaup and other birds utilize during spring migration. "This is a huge endeavor," said Zenner. "Essentially, our focus is to examine groupings of wetlands that have been divided into eight eco-regions. Our study area runs from central Iowa to Riding Mountain National Park in western Manitoba." One of the things scientists are most interested in is population densities of invertebrate animal life. Invertebrates such as amphipods -- a tiny crustacean resembling fairy shrimp -- are critical for building nutrient reserves needed for [scaup] egg production. Studies are also examining aquatic plant life, existing fish populations, water clarity, chemical and other pollutant contamination. "Water quality sampling began in 2003, and what we're finding is that scaup are currently unable to find the essential food items that were historically available in mid-western wetlands," said Zenner. "Important aquatic foods have disappeared as our wetlands have become horribly degraded during the past 25 years. This should come as no great surprise since our marshlands are stuck in the middle of the most intensively farmed region in the entire Midwest." For lesser scaup to maintain the healthy body condition needed for egg production, they must have amphipods, says Zenner. Historically, it was no problem to find that nutritional source in Iowa. Today, wetland water quality has been compromised to the point that amphipods no longer exist in most marshlands. Migrating ducks are now forced to feed on other, more pollutant-tolerant inverts -- such as snails. But even these alternate food sources may be in short supply. Consequently, scaup end up surviving on things like aquatic seeds or bloodworms, which are insufficient to increase or even maintain body weights. Here's the alarming truth. In terms of amphipod, snail, mollusk, and other important invertebrate food families --- Iowa ranks at the very bottom of all wetland groups examined from central Iowa to Canada. At the same time, Iowa is at the very top of the list for nitrates, phosphorus levels, rough fish densities, low water clarity, and the sad list goes on. "I think that everyone living in Iowa should be very dismayed by these findings," said Zenner. "It has now become very evident that our state's wetlands are not as healthy as they appeared at a glance. We've learned that the quality of any Iowa wetland is simply a mirror image of the quality of its watershed. Protecting or improving those watersheds has become our next challenge." - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - To get off the IOWA-TOPICS list, send any message to: [log in to unmask]