The Ghost Birdies are the ghosts of five non-anthropomorphic birds.
These five birds met their fate in the 19th century in the jaws of one of the cats owned by the mortal masters of Gracey Mansion. They were comically buried in a circle around the cat himself, as if mobbing around him in a thirst for justice. Indeed, the Cat's ghost is somewhat obvious to this, the five diminutive ghosts do in fact bear him a terrible grudge and never miss an opportunity to peck at him.
Behind the scenes
The Birdies' tombstones were among the additions to the Disneyland Haunted Mansion’s Pet Cemetery tableau in 1993.