More to explore:
Mosaic Birdbath | Birds & Blooms-another idea of how to line a mini terra cotta bird bath
Totally digging the idea of repurposing a terra cotta flower pot into a mosaic bird bath!
DIY Mosaic Bird bath crafts-and-creations with flower pots
Terracotta Pot Mosaic Bird Bath
Mosaic Bird Bath : Directions. Uses clay pots and planter base. Looks easier than some others; good place to begin. Also, concrete ones are VERY heavy and might topple over on pets/children.