Presumably, Wali has the same backstory as his fellow flock members. Like Chewa and his gang, Wali likely flourished during Scar's reign, as animals dropped dead daily in the hot desert due to the Lion King's poor rule. Come Simba's reign, food is harder to find, for the new king is much more responsible than the last, and Wali presumably starves alongside his vulture friends.
Wali is a member of Chewa's flock. He is one of the more eager vultures who shows great interest in eating Kopa. His hungry words end up exploiting Kopa's royal stature, which ultimately saves the cub's life, as Chewa decides to keep Kopa in order to hold him ransom.
Personality and traits
Wali's personality is not explored in the book. However, the few scenes that he appears in depict him as being an eager and selfish bird, much like his fellow vultures. By mocking Kopa, Wali reveals himself to be cruel and uncaring, as he is willing to kill a young cub in order to fill his own belly.