Smirch

Smirch is a purple bird with a wicked beak, who lives in the poorest area of the Metropolis Zone. He is a master thief, capable even of bypassing the Floating Island's defences and stealing the Purple Chaos Emerald from under the nose of Knuckles himself! He attempted to sell the Emerald to an interested buyer (actually Knuckles in disguise), but was prevented and eventually caught by the combined efforts of Sonic and Knuckles.