Duck is a proper or common noun?

Yes, the noun duck is a common noun, a Word for any duck of any kind.

A proper noun is the name of a specific person, place, thing, or a title; for example:

• Daffy Duck
• Duck, NC 27949
• Duck Lake, Clarence, MI
• Duck House (restaurant), Monterey Park, CA
• "Duck Soup", 1933 movie with Groucho and Harpo Marx