Modifiers matching duck:

• tenacious,
• rare,
• bullying,
• slobbery,
• jealous,
• unusual,
• determined,
• native,
• optimistic,
• boastful,
• pushy,
• insecure,
• marine,
• zany,
• wild,
• larger,
• paranoid,
• indigenous,
• common,
• brash,
• short-tempered,
• here,
• daffy,
• domestic,
• large,
• breeding,
• aggressive,
• smaller,
• small,
• lisping,

Simple categories matching tenacious:

• person,
• artist,
• hero,
• mathematician,
• duck,
• professor,
• student,
• bully,
• detective,
• queen,
• warrior,
• policeman,
• campaigner,
• terrorist,
• scientist,
• friend,
• royal,
• journalist,
• reporter,
• thug,
• lover,
• genius,
• recluse,
• womanizer,
• cop,
• adventurer,
• soldier,
• layer,
• sportsman,
• villain,
• pioneer,
• athlete,
• conservative,
• explorer,
• aristocrat,
• feminist,
• metal,
• gladiator,
• bureaucrat,
• presenter,
• sailor,
• magician,
• neighbour,
• general,
• boxer,
• hunter,
• spy,
• child,
• pilot,
• material,