One of the key aspects of natural selection is competition, yet the concept of competition is not necessarily emphasized in explanations of natural selection. Because of this, we developed an activity for our class that focuses on competition and provides an example of the effects of competition on natural selection. This hands-on activity models the field study completed by David Lack on Darwin's finches. By using this historical study, we also give students an example of the nature-of-science concept of multiple methods. Although this activity was created for a college introductory biology course, it is appropriate for high school. We also provide an additional objective for upper-level ecology and evolution courses.