A software development screencast is a video that captures the screen of a developer working on a particular task while explaining its implementation details. Due to the increased popularity of software development screencasts (e.g., available on YouTube), we study how and to what extent they can be used as additional source of knowledge to answer developer's questions about, for example, the use of a specific API. We first differentiate between development and other types of screencasts using video frame analysis. By using the Cosine algorithm, developers can expect ten development screencasts in the top 20 out of 100 different YouTube videos. We then extracted popular development topics on which screencasts are reporting on YouTube: database operations, system set-up, plug-in development, game development, and testing. Besides, we found six recurring tasks performed in development screencasts, such as object usage and UI operations. Finally, we conducted a similarity analysis by considering only the spoken words (i.e., the screencast transcripts but not the text that might appear in a scene) to link API documents, such as the Javadoc, to the appropriate screencasts. By using Cosine similarity, we identified 38 relevant documents in the top 20 out of 9455 API documents.