TASK DEFINITION: You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.
PROBLEM: Category: ANCIENT GREEKS 
Clue: This actor of the 6th century B.C. is credited with introducing the use of masks on stage

SOLUTION: thespis

PROBLEM: Category: RED, WHITE OR BLUE 
Clue: Jack London's follow-up doggie tale to "The Call of the Wild"

SOLUTION: white fang

PROBLEM: Category: WHAT'S THE MATTER...YELLOW?? 
Clue: Call it crazy, but unlike other types of these birds, the yellow-billed one builds its own nest instead of invading

SOLUTION:
cuckoo