The Random Writers Forum Grammar game!

The grammar game is that you have to find the grammatical error in this one paragraph. It's going to be hard!

  The oozing red blood dripped from its hazel claw and black feathers. It cawed a lonely caw and crumpled to the ground as the moon shone on it's glossy feathers. A siren's song floated throughout the still night air and broke the calm rhythm of the full moon. No longer caged, but confined within its weaknesses.

Shouldn't  there be a comma separating the words that describe the blood? If not, then I have no idea. XD