Cooperative Fish and Wildlife Research Units Program: Iowa
Education, Research and Technical Assistance for Managing Our Natural Resources

Iowa Project

Estimating Breeding Populations of Canada Geese in the Midwest – A Model to Predict Canada Goose Breeding Pair Densities Using National Wetlands Inventory Data

July 2012 - September 2017


Participating Agencies

  • Iowa DNR

Mississippi Flyway Council states and provinces have been developing and refining methods to estimate the giant Canada goose populations in the Flyway since 1993. Numbers of giant Canada geese in the Mississippi Flyway appear to exceed the combined total of all other Canada goose populations in the Flyway, but estimates of giant Canada goose populations in states and provinces are imprecise in many cases. Canada geese are the second most frequently harvested waterfowl in the Flyway and are extremely important to waterfowl hunters . Sound science-based management of giant Canada geese, as well as other goose populations in the Flyway, requires more precise estimates of the breeding populations of these birds in the states and provinces with resident populations of these birds. The Iowa DNR has been surveying the breeding population of Canada geese in Iowa since 1993. The survey methodology has evolved as computing tools and GIS information has improved. The surveys conducted in Iowa and surrounding states indicate that the key to precisely estimating the Canada goose breeding population in a region is the accuracy of the stratification of the universe of survey plots in the region. Because we now have a revised and refined wetlands inventory for Iowa (circa 2002), as well as 5 years of Canada Goose observation data (from aerial surveys of 160 2 mi2 plots/year) that ties all the observations of geese (singles, pairs, and groups) to specific wetlands or streams/rivers on individual survey plots, we are in an excellent position to develop a model (or models) that will predict the Canada goose population for each section in the state based on number, size, and types of wetlands (and possibly adjacent upland habitat) in each section. However, it will take considerable computing and GIS work to develop the model or models necessary to make these predictions. OBJECTIVES The overall objective of the project is to develop a methodology to estimate the number of breeding pairs of giant Canada geese per section using National Wetlands Inventory and aerial survey data. Specifically, we will: 1. Reclassify the wetlands identified in the 2002 NWI for Iowa, which are currently classified according to the Cowardin system, to the 5-Class Stewart and Kantrud (1971) system. 2. Identify all sections in the state with potential Canada goose nesting habitat. 3. Develop a model or models that predict the numbers of breeding pairs of Canada geese that could be found in each section. 4. Assign sections to strata based on their predicted numbers of breeding pairs. Appropriate strata will be identified based on the analyses of previous surveys, which grouped sections into 4 strata. 5. Ground-truth aerial counts of Canada geese on plots with high densities of breeding pairs (Cordts et al. 2002) and calculate visibility correction factors if appropriate. 6. Determine giant Canada goose nest success (Dinsmore et al. 2002) at Rice Lake and Elk Creek Wildlife Management Areas where nest densities have historically been very high