Habitat fragmentation, striped skunks, and waterfowl nest predation

In North America, expansion of agriculture has resulted in the fragmentation of grasslands. Consequently, waterfowl populations have declined due to predation on nests. Predation on nests is an old evolutionary force affecting waterfowl, but the recent fragmentation of grasslands may have yielded a situation to which waterfowl are not yet adapted. In southcentral Saskatchewan, striped skunks are a major predator, and the interactions between fragmentation, striped skunks, and waterfowl are unknown, and were the major goal of my thesis. First, I examined the patterns of den site selection in striped skunks. Farmsteads are the most preferred habitat for den sites, and that within farmsteads, striped skunks denned under buildings. Alternatively, resting sites were preferably located in farmsteads and wetlands, whereas managed nesting areas, woodland, and cropland were avoided. When foraging within their home ranges, striped skunks preferred habitats such as wetland and woodland where their main food items, insects and small mammals, are most abundant. Cropland contained little food, and was strongly avoided. Use of specific habitats decreased with distance from the habitat edge, suggesting that large patches of nesting habitat may provide a refuge for ground nesting birds. Lastly, I performed a field experiment to assess the effects of nest density and nearest neighbours on nest predation. Density effects did not occur during the early breeding seasons of waterfowl (May 15-June 13), even across a 10-fold difference in nest density (2.5-25 nests/ha). However, density effects were significant in the late breeding season (June 15-July 14). Nearest neighbour effects were present at intermediate and high densities, but rarely observed at low density. Also, nearest neighbour effects occurred faster during the late breeding season, suggesting that striped skunks recognized and keyed on high-density nesting patches. This confirms that at current nest density (typically