Semester of Graduation

Fall

Degree

Master of Science (MS)

Department

Renewable Natural Resources

Document Type

Thesis

Abstract

The Prairie Pothole Region (PPR) is the most important region for ducks in North America, producing over half the ducks on the continent, and it is a priority landscape for wetland and grassland conservation. Agricultural expansion has changed the PPR, and the majority of grasslands and potholes have been converted into row-crops. The loss of nesting habitat has directly caused nest success to decline. Most of the remaining wetlands are surrounded by row-crops, and are considered lower quality because they receive runoff of sediment and chemicals, which may decrease primary forage for young ducklings as well as inhibit wetland vegetation. Wetland quality and the availability of forage may influence brood abundance in wetlands in crop-dominated landscapes.

I surveyed wetlands in row-crop dominated landscapes of the eastern PPR in the United States. Over two summers, I surveyed wetlands for broods and sampled wetlands to quantify the aquatic invertebrates available for ducklings. I detected 345 broods and sampled 230 unique wetlands. I used N-mixture models to evaluate factors that influence brood abundance with, based on biologically relevant covariates measured at the wetland level. Brood abundance was positively associated with the abundance of aquatic invertebrates and the amount of grassland surrounding the wetland. I then examined the factors within the wetland that may influence the aquatic invertebrates available for ducklings. I used linear mixed effects models to determine which variables influenced forage abundance, while controlling for effects of year and sampling round by assigning them as random effects. The strongest and most consistent effect I uncovered was that invertebrate abundance decreased as DO concentration and wetland depth increased. Row-crop expansion in the PPR is a concern for waterfowl production, with most conservation efforts going to wetlands surrounded by grasslands. I consistently found broods using wetlands embedded in agriculture. Brood abundance was influenced by grassland and aquatic invertebrates and aquatic invertebrates were most influenced by DO concentrations and wetland depth. The wetlands in my study are most at-risk but my study indicates that they provide valuable habitat for broods through the summer months and should be conserved.

Committee Chair

Kevin Ringelman

DOI

10.31390/gradschool_theses.5460

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