PIEDMONT (CBS SF) — The Piedmont High School Bird Calling contest, originally organized by science teacher Leonard J. Waxdeck, celebrated its 50th anniversary Friday night in the Alan Harvey Theater on the Piedmont High campus.

Students tweeted their best bird impersonations to compete for one of the top positions which comes with an invitation to appear on CBS Late Show with David Letterman. Two students were named winners of Friday night’s event and will be on their way to New York next week.

Contestants were judged on their knowledge of birds, drama and humor.