Ravens are fat, black birds which appear in Super Mario World 2: Yoshi's Island and Yoshi's Story. They are based on the real birds with the same name.
Ravens usually walk around an object. In Yoshi's Story, the only object to walk around is the giant ball which is seen in the Tall Tower. Yoshi must be quick to jump off the object or the Raven will bump into him and hurt him. Ravens can not be eaten.
Ravens can also be allies in Paper Mario where they live in Lavalava Island. They are also featured in Super Princess Peach where there are blue Ravens crying and moving fast. They also shriek in tears as they make the ground, balconies or platforms shake. If Peach is on the ground, she would be startled by that cry.
A notable raven is Raphael the Raven, who appeared as a boss. He was fought on the moon before being sent out into space and becoming a constellation.