A Buildr developer designs, codes, and modifies software applications or specialized utility programs using the Apache Buildr tool. They use this Java-based build tool to manage and automate the project's build process. The developer is responsible for scripting, debugging, and testing the code to ensure it is error-free and efficient. They handle dependencies, utilize libraries, and manage the project’s versioning. Additionally, they may collaborate with other developers, participate in code reviews, and document the project's build process. Their goal is to create a streamlined, effective, and automated build process that improves the project's efficiency and quality.