This study tested an iPad application using a dichotomous key as a scaffolding tool to help students make more detailed observations as they identified various species of birds on display in a museum of natural science. The Mobile Dichotomous Key (MDK) iPad application was used by groups of fifth- and seventh-grade students. Analysis of the findings suggests that the MDK was equally as effective and in some ways more effective than the educator-led intervention at improving students' scientific observation skills. In general, the scaffolding key in both mobile and educator-led form was found to be more effective for fifth-grade students than for seventh-grade students. In addition, it was found to be effective at improving the level of detail students provided and the number of scientific terms they used, but not at improving the number of valid inferences students made.