Date of Award
5-1-2012
Degree Name
Master of Science
Department
Zoology
First Advisor
Eichholz, Michael
Abstract
Conservation efforts to increase duck production have led the United States Fish and Wildlife Service to restore grasslands with multi-species (3-5) mixtures of cool season vegetation often termed dense nesting cover (DNC). The effectiveness of DNC to increase duck production has been variable, and maintenance of the cover type is expensive. In an effort to decrease the costs of maintaining DNC and support a more diverse community of wildlife, restoration of multi-species (16-32) plantings of native plants has been explored. Understanding the mechanisms of nest site selection for nesting ducks within these plantings is important in estimating the efficiency of this cover at providing duck nesting habitat and determining appropriate management techniques. I investigated the vegetation characteristics between the 2 aforementioned cover types in the prairie pothole region of North Dakota, USA to see if native plantings provide the same vegetative structure to nesting hens as DNC. I also determined the nest density and nest success of upland nesting waterfowl in the cover types to determine if restored native plantings are providing the same nesting opportunity as DNC. Within each cover type I identified vegetation characteristics at nest sites of the 5 most common nesting species and compared them to random locations and within species to identify species specific factors in nest site selection. I located 3,524 nests (1,313 in restored-native vegetation and 2,211 in DNC) of 8 species in 2010-11. Native plantings had an average of 6.17 (SE = 1.61) nests/ha while DNC had an average of 6.71 (0.96) nests/ha. Nest densities were not different between cover types for the 5 most common nesting species. In 2010, nest success differed between cover types with restored-native plantings having 48.36% (SE = 2.4) and DNC having 42.43% (2.1) success. In 2011, restored-native planting success dropped considerably to 13.92% (1.7) while DNC success was similar to 2010 at 37.10% (1.7) The variability in nest success appeared to be impacted by late season success, as native plantings had similar success early in the nesting season, but much lower success later in the nesting season in both years. Vegetation data indicated no structural difference between cover types in 2010; however, a difference was detected during the late sampling period in 2011, with native plantings having shorter vegetation at random locations than DNC during this sampling period. In general ducks selected nest sites with greater leaf litter and denser, taller cover compared to random sites, however, vegetation density and height selection varied among species. Gadwall and mallards selected the tallest, densest vegetation, with northern pintail, blue-winged teal, and northern shovelers selecting vegetation of intermediate height and density. My results indicate native plantings are able to support similar densities of nests, but have great variability in nest success from year to year. In years with low nest success, native plantings may create an ecological sink as hens were not able to identify low quality patches and nested in similar densities despite lower success.
Access
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