PIEDMONT -- Grebes and owls and coots, oh my.

The 49th annual Piedmont High School Bird Calling Contest will swoop into town early this year. It is usually held in May but was changed to April this year because of scheduling conflicts, bird call "coach" and Piedmont High teacher Ken Brown said.

Returning champs Eli Nash, James Clifford and Gabe Bolio will try to grab the top prize again with their skit on the Red-Necked Grebe. Sophie Nadler, Alex Sieben and Zane Haney are feverishly working on their skit for the Chukar, while Jordan and Jeremy Wong are prepping for their barred owl skit.

Fifteen groups -- some trios, duos and two solo contestants -- will screech and flap their way to fame, they hope. The winners and at least one runner-up will appear in mid- to late May on "The Late Show with David Letterman," an annual tradition.

Before Letterman, the students appeared for 17 years on "The Tonight Show with Johnny Carson."

The contest was the brainstorm of Piedmont High teacher Leonard Waxdeck in 1963, the same year that Alfred Hitchcock's "The Birds" premiered -- with birds run amok. Waxdeck passed away in 1994, but his legacy continues.

Brown works with the groups to develop their ideas and offers guidance on where to find bird calls. The Piedmont High students practice at lunchtime and after school or gather off campus.

"Some kids have the skit in mind but are not sure of what bird -- and the other way around," he said.

One nifty website Brown found for bird calls is www.allaboutbirds.org. Brown is glad to see even more groups than last year, which saw about nine groups competing.

As always, the event promises to be a sellout -- all 440 seats of Alan Harvey Theater.

Brown is encouraging the groups to offer variety in their calls.

"There can be a call to chicks, a mating call, a fighting call," he said. "The audience and the judges like variety."

Groups will be judged on authenticity of the calls, poise and delivery and pertinent information about their bird incorporated into the sketch.

IF YOU GO
What: 49th Annual Piedmont High School Bird Calling Contest
When: 7 p.m. Friday
Where: Alan Harvey Theater, 800 Magnolia Ave.
Cost: $20 reserved; $12 general; $8 students and seniors
Tickets: http://tinyurl.com/birdcalling or 510-594-2626