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."

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