Waterfowl Numbers Up
By Lowell Washburn
Iowa Department of Natural Resources
Posted: August 19, 2003

DES MOINES--When Iowa hunters take to the state's public wetlands this fall, they are likely to encounter more migrating ducks than they did one year ago.

According to DNR Waterfowl Biologist, Guy Zenner, all of the continent's 10 most commonly surveyed duck species showed an increase during this year's nesting season. For several species, the gains were dramatic. A drake wood duck takes a break along a Winnebago River backwater.  According to DNR wildlife biologists, wood ducks, along with blue-winged teal and mallards, enjoyed excellent production on Iowa wetlands during 2003.  In the prairie regions of southern Canada, duck production increased substantially over 2002, and a strong fall migration is predicted.    DNR photo by Lowell Washburn

The number of blue-winged teal increased by 31 percent over last year, while pintails jumped 43 percent. The number of shovelers increased by 56 percent and the breeding populations of green-winged teal, gadwalls, redhead, and canvasback ducks all showed gains of around 15 percent over 2002. The number of scaup and mallard ducks showed a more moderate increase of 6 percent over last year. The number of wigeon rose by 9 percent.

According to the U.S. Fish & Wildlife Service, the 2003 population of mallard, gadwall, teal, redhead, and canvasback ducks is now at or above the long term [1955-2003] average for those species.

"FOR IOWA WATERFOWL HUNTERS, any increase in duck numbers is welcome news," said Zenner. "But this year, duck numbers are up quite significantly from what was surveyed during the spring of 2002. Consequently, the outlook for this year's fall flight is very positive." A drake redhead rests on a northern Iowa wetland.  The number of redheads, along with all other species of prairie nesting ducks, has increased significantly from last year.   DNR photo by Lowell Washburn

But this year's sudden increase in total duck numbers comes as no surprise, says Zenner. Given the greatly improved spring habitat conditions that greeted migrating ducks during April and May, it would have been hard for bird numbers not to increase.

Simply put, ducks need water to nest. An abundance of spring ponds generally means a surge in production. When drought conditions cause spring ponds to disappear, waterfowl populations decline.

During this year's spring habitat surveys, May pond counts increased by 145 percent across the principal nesting grounds of prairie Canada. Pond counts in the grasslands of North Dakota, South Dakota, and eastern Montana increased by more than 30 percent.

"It would have been very unusual to have pond numbers increase this dramatically and not have duck numbers follow that trend," said Zenner.

"Last winter was extremely dry across much of southern Canada. During April, those areas were hit with a combination of heavy snow storms and abundant rainfall. The ducks arrived and took full advantage of the improved habitat."

BUT WILDLIFE BIOLOGISTS ARE QUICK TO CAUTION hunters against placing too much emphasis on total duck numbers. That, they say, can be misleading.

"What waterfowl hunters living in places like Minnesota or Iowa need to keep in mind is that hunting success will depend much more on developing fall weather patterns and regional habitat [marsh] conditions than it will on the total number of ducks coming out of Canada," said Zenner.

"Right now, conditions are extremely dry across much of the state. In the marsh country of north central and northwest Iowa, persistent heat and a lack of rainfall have degraded wetlands significantly during the past month. We need substantial rainfall to raise wetland water levels and pull birds into Iowa during migration. Otherwise, migrants could just fly over or even bypass those areas this fall.

"However, it should also be noted that a couple of good cloud bursts could turn things around. With favorable moisture patterns, the whole picture could change completely within a few days -- we've seen that before. At this point, we'll just have to wait and see what the weather does.

"What I can say is that regardless of where a person plans to hunt this fall, some preseason scouting is definitely in order," said Zenner.