Modifiers matching duck:

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

Simple categories matching boastful:

• bully,
• person,
• hero,
• aristocrat,
• warrior,
• ceo,
• motorcyclist,
• writer,
• sportsman,
• duck,
• playboy,
• narcissist,
• businessman,
• billionaire,
• sculptor,
• politician,
• god,
• child,
• actor,
• adventurer,
• comedian,
• athlete,
• outdoorsman,
• entertainer,
• clown,
• composer,
• king,
• hunter,
• emperor,
• publisher,
• boxer,
• father,
• artist,
• showman,
• painter,
• novelist,