You have been asked to determine on what types of grasslands two species of birds, northern harriers and short-eared owls, build nests. The types of grasslands to be used include undisturbed native grasses, managed native grasses, undisturbed nonnative grasses, and managed nonnative grasses. You are allowed a plot of land 500 meters square to study. Explain how you would determine where to plant the four types of grasses. What role would random assignment play in this determination? Identify any confounding variables. Would this study be considered an observational study or an experiment? (Based on the article “Response of Northern Harriers and Short-Eared Owls to Grassland Management in Illinois,” Journal of Wildlife Management [1999]: 517– 523.)