Upper Mississippi River National Wildlife Refuge staff members, Bill Thrune and Brian Stemper fly one of their weekly Fall surveys counting waterfowl. - Photo copyrighted and taken by Robert J. Hurt

Last fall, a record number of tundra swans used the Upper Mississippi River National Wildlife and Fish Refuge as a stop-over point during migration.  On November 20, the Refuge held 52,070 swans, 31,000 were in the Wisconsin Islands Closed Area in Pool 8 near Brownsville, MN. The previous record was 34,730 swans on November 22, 2005. Counts since the mid 1990s ranged from 15,000 to 32,000 birds.

Refuge biologist Eric Nelson said, “The birds zeroed in on Pool 8 for three primary reasons, 1) the positive effects of the Pool 8 drawdown continue to produce duck foods, 2) restored islands protect birds and aquatic plants from cold winds and erosive wave action, and 3) the Wisconsin Islands Closed Area (closed to hunting) worked well by reducing human disturbance thus providing swans a secure place to feed in peace. The swans really fueled-up for their final push to wintering areas of Chesapeake Bay and the North Carolina coast.”

The Refuge plays a crucial role in providing abundant habitat for migrating waterfowl along the Mississippi Flyway. One way of evaluating the habitat is to monitor bird use with counts made during weekly aerial surveys. In 2006, surveys began October 2 and continued through December 6, near the end of duck hunting and before total freeze-up.

Back in the office, biologists use the survey data to document peak numbers and calculate waterfowl use- days. Peak counts are comparable, but they do not tell the whole story. Use-days reflect how many days the birds stay.  Nelson said, “We learn from the birds how we’re doing. The more days they stay, the better the food source. The birds wouldn’t stay as long if the food and security wasn’t here.” 

Waterfowl use days are calculated by taking the average number of birds counted between two counts multiplied by the number of days between those counts.   For example, if the first count has 1,000 birds, and second count eight days later has 2000 birds there would be 12,000 use-days (average count =1500 x 8 days). 

The number of use-days for all ducks, swans, and geese using the Refuge this fall was a big number - over 19 million. Winona District Biologist Lisa Reid says, “It’s a huge number because the refuge is a major component of the Mississippi Flyway. For example, the arrowhead bed in the Wisconsin Islands Closed Area was fabulous this year. So they had a reason to stay.”  When Reid finished her calculations there were over 1.2 million swan use-days on the refuge. Many more than previous years.

In the case of tundra swans, peak counts increased 50% from 2005 to 2006, whereas swan use-days increased 150%.  Not only were there more birds but they stayed longer in 2006.  The importance of the Refuge to migrating swans is on the increase. 

The birds act like a report card and this year waterfowl seem to be giving the Refuge an A+ on habitat in Pool 8.