| The habitat selection process of greater sandhill cranes Grus canadensis tabida in Wisconsin was studied as a nested hierarchy with three natural levels: within the geographic range of the population, the differential use of landscapes composed of varying proportions of land covers; within home ranges of breeding and non-breeding cranes, the differential use of habitat components in a landscape with mixed agriculture, wetlands, and forest; and within one habitat component of the home range, the differential use of agricultural fields at four different farming stages.; I hypothesized at least one type of land cover or landscape structure feature could explain the distribution pattern of sandhill cranes at a broad scale. I explored the relationship between key environmental factors and densities of breeding and non-breeding cranes. Proportion, size, shape, and adjacent patch types for emergent/wet meadow wetlands profoundly influenced crane densities. Agricultural fields, either by composition or configuration, had a neutral effect. Presence of forest negatively affected the positive relationship between crane densities and wetlands.; Within home ranges of breeding and non-breeding cranes, I hypothesized that crane distribution has clustered patterns in space, caused by uneven resource distribution. Breeders versus non-breeding flocks differ in the sizes and locations of their home ranges, such that land cover types and proximity to wetlands can predict where the cranes will occur. The habitat use patterns of both social units appear closely related to food resource availabilities as influenced by agriculture practices.; At a finer level of habitat selection, I determined that agriculture practices---crop type, rotation of crops between years, crop stages within the growing season (crop stubble, plowed, planted, and germinated fields)---altered habitat use patterns of cranes. These studies examine how the dynamic interaction of habitat components in time and space influences sandhill crane population densities and habitat use patterns. Based on a hierarchical structure, I identified factors operating at different levels of the habitat selection process and tested explanations for these patterns. This dissertation provides insights about the ecology and successful management of cranes from regional scales to the level of individual farm fields---context and history both emerge as important. |
