Hah! Alex just forced the woman to change her answer from "What is a gull" - Be more specific, Alex said - to "What is a seagull?"
But "seagull" is as wrong as "Canadian goose". "Gull" is the preferred term - for one thing, many of them live nowhere near the sea. And while most birders probably don't leap to correct people who say it, for Jeopardy! to insist on the wrong term (I mean, it's not like she said "shore birds", after all) is peculiar at best.
Good thing she "corrected" herself in time not to lose the question!