Mallard Study

Evaluation of the effects of habitat restoration on abundance and productivity of mallards in the Eagle Lake Complex (northern Iowa)


Background| Partners | Project Overview | Objectives | Literature Cited | Contact Information


As part of the Prairie Pothole Joint Venture (PPJV), a priority initiative of the North American Waterfowl Management Plan (NAWMP), the Iowa Department of Natural Resources (IDNR) has a goal of protecting and enhancing 30,000 acres of wetland and upland habitat in the 35 counties that encompass the prairie pothole region in Iowa (Gladfelter 1988). The primary strategy used to achieve this goal has been to acquire previously drained and existing wetlands, restore the drained wetlands, and improve adjacent upland habitat for nesting waterfowl. Although wetland protection and restoration provide habitat for wetland wildlife (LaGrange and Dinsmore 1989, Delphey 1991, Hemesath 1991), especially waterfowl (Zenner et al. 1997), it is important to determine if the presently employed habitat protection and enhancement practices are achieving the objective recruitment rate in intensively farmed areas likes Iowa's prairie pothole region. It is also important to determine the most cost-effective management strategies that can be applied to the Iowa landscape to increase waterfowl recruitment.

The PPJV Management Board has set a goal of achieving an average recruitment rate of 0.6 for the mallard population in the PPJV region. Evaluation efforts in the Prairie Habitat Joint Venture (Canada) use the mallard productivity model and waterfowl population and habitat data obtained from the Four-Square-Mile Waterfowl Breeding Pair Survey (FSMS). The mallard model is a flexible computer program that requires the user to specify numerous input values to obtain projections of recruitment. The FSMS and the mallard productivity model were developed by the staff at the Northern Prairie Wildlife Research Center, Jamestown, North Dakota, using biological information that was primarily collected in the north-central portion of the prairie pothole region (Johnson et al. 1987, Cowardin et al. 1988). Thus the average input values used in the model primarily reflect mallard ecology in North Dakota. Because of differences in land use, habitats and habitat distribution on the landscape, climate, and waterfowl migration and nesting chronology, the model inputs may not reflect mallard ecology in Iowa. To adequately apply this computer tool to the prairie pothole region in Iowa, data for the ecological parameters used in the model should be collected in this region.

Another major concern of wetland restoration projects is how to evaluate whether the restoration is successful. Because providing excellent wildlife habitat is an acknowledged function of wetlands, wildlife components should be included with other wetland functions as measurable success criteria. Important components of bird populations that can be evaluated are productivity, species diversity, and abundance.


Iowa Department of Natural Resources: The IDNR is the major supporter of this study. Permanent staff and temporary field assistants hired by them are vital elements of the study. Guy Zenner, the state waterfowl biologist, is assisting with planning, logistics, hiring assistants, and supervision. Guy also prepared much of the text in this file.

Iowa Cooperative Fish and Wildlife Research Unit (ICFWRU): Rolf Koford is overseeing the project and Gian Dodici, a Ph.D. student, has the major responsibility for conducting the research.

Iowa State University: ISU provides administration of the project. Bill Clark, in the Department of Animal Ecology, co-advises Gian.

The U.S. Fish and Wildlife Service: The Region 3 office is supporting the study.

Project Overview:

We are estimating abundance and productivity of mallards on wetlands and uplands that have been restored in the Eagle Lake North American Wetland Conservation Act (NAWCA) project area in the eastern half of Iowa's prairie pothole region (Hancock and Winnebago Counties). The restored wetlands and reconstructed grasslands of the Eagle Lake Complex are representative of the kind of restoration of bird habitat that has been and can be conducted in the highly agricultural landscape of the Midwest. This area is also targeted for PPJV activities. The study area will be approximately 20-28 square miles in size, i.e., 5-7 adjacent FSMS plots, and contain a complex of wildlife management areas (WMA) and waterfowl production areas (WPA) that have recently been established or enlarged through acquisition. Developing large complexes of restored wetlands and grasslands has been the primary strategy of both the NAWCA and PPJV programs in Iowa and the study area selected will permit the evaluation of this strategy as well as provide information on duck use of other habitat components of the landscape.

This study provides the basic information necessary to adjust input parameters and customize the mallard model, thereby improving the model's abilities to predict duck recruitment in the southern part of the prairie pothole region. This study also will provide important information on the habitat patch size and duck productivity in an area of the prairie pothole region where habitat fragmentation is most severe. This information will be particularly useful in designing and locating new WPAs in intensively farmed environments.

An important objective of this project is to estimate pre- and post-restoration bird-population characteristics. Because no data were obtained before the project began, we will need to model population characteristics based on pre-project land cover and habitat conditions.


1) Map the habitat to quantify current land cover and estimate changes in cover as a result of restoration activities.

2) Estimate the mallard breeding population in the Eagle Lake Complex.

3) To estimate the various components of mallard productivity in the Eagle Lake Complex, such as the conditional probability that a hen will be killed if her nest is destroyed, hen summer- mortality rate, habitat-specific nest survival rates, number of nests per hen, hen success (proportion of hens that hatched a nest), nest success, average clutch size.

4) Estimate pre- and post-restoration waterfowl-population characteristics.

Literature Cited and Associated References:

Bishop, R. A. 1981. Iowa's wetlands. Proc. Iowa Acad. Sci. 88:11-16.

Carlson, J. D., W. R. Clark, E. E. Klaas, and P. A. Opler. 1993. A model of the productivity of the northern pintail. U.S. Fish Wildl. Serv., Fish Wildl. Biol. Rep. 7. 20pp.

Cowardin, L. M., D. H. Johnson, T. L. Shaffer, and D. W. Sparling. 1988. Application of a simulation model to decisions in mallard management. U.S. Fish Wildl. Serv., Fish Wildl. Tech Rep. 17. 28pp.

Delphey, P. J. 1991. A comparison of the bird and aquatic macro-invertebrate communities between restored and 'natural' Iowa prairie wetlands. M.S. Thesis. Iowa State Univ., Ames. 85pp.

Gamble, K. 1996. Waterfowl harvest and population data. U.S. Fish and Wildl. Serv. Unpubl. Rep. 80pp.

Gladfelter, L. 1988. Iowa Prairie Pothole Joint Venture implementation plan. Iowa Department of Natural Resources, Des Moines, IA. 40pp.

Hemesath, L. M. 1991. Species richness and nest productivity of marsh birds on restored prairie potholes in northern Iowa. M.S. Thesis. Iowa State Univ., Ames. 87pp.

Humburg, D. D. 1976. The social organization of a mallard population in northern Iowa. M. S. Thesis. Michigan State Univ., East Lansing. 31pp.

Johnson, D. H. 1979. Estimating nest success: the Mayfield method and an alternative. Auk 96:651-661.

Johnson, D. H., D. W. Sparling, and L. M. Cowardin. 1987. A model of the productivity of the mallard duck. Ecol. Modeling 38:257-275.

Klett, A. T., H. F. Duebbert, C. A. Faanes, and K. F. Higgins. 1986. Techniques for studying nest success of ducks in upland habitats in the prairie pothole region. U.S. Fish Wildl. Serv., Resourc. Publ. 158. 24pp.

Krapu, G. L., D. H. Johnson, and C. W. Dane. 1979. Age determination of mallards. J. Wildl. Manage. 43:384-393.

LaGrange, T. G., and J. Dinsmore. 1989. Plant and animal community responses to restored Iowa wetlands. Prairie Nat. 21:39-48.

Orthmeyer, D. L., and I. J. Ball. 1990. Survival of mallard broods on Benton Lake National Wildlife Refuge in north-central Montana. J. Wildl. Manage. 54-62-66.

Ohde, B. R. 1980. Mallard breeding strategies and attempts to alter the sex ratio. M. S. Thesis. Iowa State Univ., Ames. 47pp.

Rotella, J. J. 1990. Habitat use, movements and survival of mallard broods in southwestern Manitoba. Ph.D. Thesis. Univ. of Idaho, Moscow. 66pp.

Sharp, D. E., and J. T. Lokemoen. 1987. A decoy trap for breeding-season mallards in North Dakota. J. Wildl. Manage. 51:711-715.

Zenner, G. G. 1977. Breeding behavior of mallards (Anas platyrhynchos) in north-central Iowa. M. S. Thesis. Univ. of Minnesota, St. Paul. 114pp.

Zenner, G. G., J. K. Kienzler, T. G. LaGrange and W. A. Fuller. 1997. Waterfowl use of restored wetlands in Iowa. (In progress).


Rolf Koford
Iowa Cooperative Fish and Wildlife Research Unit
Science Hall II
Iowa State University
Ames, IA 50011
Phone: (515) 294-3057
Rolf Koford's Homepage

This URL:

Last Updated on August 15, 2000