In “Urban Bird-Watching,” previously published in Science Scope, the author described an activity designed to get students out of the classroom and into the outdoors (Rodenberg, 1993). In that activity, suggestions were offered to familiarize students with urban, rural, woodland, and river habitats as well as common birds of Eastern cities. This activity continues the outdoor theme by exploring bird populations and ecosystems. Students use math and probability to analyze differences in counts of three species of birds. Students also analyze the role of an introduced species, the European starling, in the urban environment.