Ayumi Mills's Lighthearted came to mind. Oh it was fun to use it again, and I think it is a perfect fit for Erin's Sweet Tweet projects. (I was pretty pleased that when my project called for a crocheted edging that wasn't in my skill-set, I was able to substitute with a flange made with one of Ayumi's prints.)
Erin's book gives a helpful overall description of raw-edge appliqué for the birds, then each project has a more detailed diagram and tips for the sketch stitching (aka sketch appliqué or free-motion appliqué) necessary. In my case, the tree was easily manageable, and I really had fun with it.