Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange
Abstract
Since 1987 the Waterfowl Breeding Populations and Production Estimates, also called the Four Square Mile Survey, has been conducted annually in the U.S. Prairie Pothole Region. The survey was designed to assess the influence of the Small Wetlands Acquisition Program on contributions to continental waterfowl populations (Cowardin et al. 1995). Each year cooperators visit sample wetlands during two survey periods, collecting data on observed waterfowl and pond conditions. Along with ground counts, aerial photography of sample areas is collected annually, capturing habitat conditions. My objective was to assess the influence of local and landscape factors on duck pair densities. Local factors are attributes immediately adjacent to, or within, an individual wetland that affect wetland appearance or function. Landscape factors represent wetland functions within varying compositions of upland cover types and wetland densities within Four Square Mile Survey plots. I evaluated multiple years of aerial imagery (1996, 2001, 2006, and 2011) and found few differences in feature types over the 20-year period. My technique analysis revealed that ocular (on screen) estimates of open water and trees were best at the sample pond boundary and within a 20 m buffer. Grass estimates generated from National Land Cover Data (2011) were best within the 48 m and 91 m buffers. I used an Akaike’s information-theoretic approach to assess several competing models at local and landscape scales. At the local scale, the best model that reflected the relationship between duck pairs and features showed wetland area, percentage of years dry, wetland regime, and percent open water to be the most influential factors. At the landscape scale, the best model included data pertaining to the number of wetlands present, total wetland area, and terrain ruggedness within each plot. Regardless of scale, trees were not found to be a specific deterrent to duck pairs settling
