"We need that bird," yells 11-year-old Danny Scheman to his friends. "Let's circle the building."

"That bird" is no backyard sparrow but an acroterion, a flying dragon, cast in copper and perched on the roof of the Corcoran Gallery of Art. At the corner of New York Avenue, the kids crane their necks and spot the rare bird, lording it over the pigeons.Triumphantly, the kids stick a black dot on the picture of an acroterion they are carrying around and go on to the next item on the architectural treasure hunt.

The treasure hunt is one of many events scheduled as part of "Celebrate Architecture Day" Saturday at the Corcoran, the Octagon House and several museums. Danny and his friends, members of an after-school architecture class that will help out on the day's activities, are giving the treasure hunt a dry run.

Kids in groups of two and three circle the building and run up and down the marble staircases in search of claustras, rosettes and pediments. They are equipped with pictures of the architectural items and a glossary of explainations.

"I found something that looks like a flower, but a light is attached to it," says 11-year-old Natasha Lesser to the group's teacher, Emily Eig. Eig agrees that the ornament around the light fixture probably meets the definition of a rosette.

Monica Cousins, 13, stands outside the gallery, staring fixedly at the pedestal one of the Corcoran lions is sitting on.

"I think that's the an-ti-fix-ae," she says, pointing to the correct ornament but stumbling over the term. Monica and the other members of the class have designed and built models of houses, created a "dream school," conducted house tours of their own homes in the Cleveland Park area, and played "architects and clients," but some of the classical architectural terms are new to them. They quickly spot the Panathenaic Frieze, and Ionic and Doric columns are all around them. Corinthian columns, however, are elusive.

"I'll give you a hint," a Corcoran staffer tells 11-year-old Elizabeth Ransom. "The items can be in the interior of the building, on the exterior of the building, or in one of the paintings."

Seizing the hint, Elizabeth races through the galleries, skipping the rooms filled with modern abstract paintings and scanning every traditional painting. Almost out of breath, she hits paydirt - a 19th-century tableau of the U.S. House of Representatives crammed full of classical architecture - including Corinthian columns.

Finally, the coffered dome, the pediment and the egg-and-dart molding have been spotted and dotted, and the search is narrowed to one item.

"I've got one to go - the fret," says 11-year-old Bram Crocker. "Did any of you guys find the fret?"

"No, we're going to the basement," comes the answer, and heels thunder on the staircase once more. Some of the kids think they can save legwork by conferring with a guard, but even after years of patrolling the gallery the guards haven't noticed the fret.

Concentration is at a high pitch as a dozen pairs of eyes search every possible place in hope of discerning the fret pattern.

"I found it," gulps 10-year-old Tom Massey. His eyes are downcast, looking lower on this particular piece of sculpture than the area that attracts the interest of most spectators. The fret pattern decorates a pedestal on which stands one of the gallery's naked ladies.

Kids and adults wanting to join the search for frets and friezes can pick up a treasure-hunt kit at the Corcoran between 11 and 4. The hunt is appropriate for fourth-graders and up, but younger kids can do it with a little help. Other events on Celebrate Architecture Day include:

Child and adult tours of architectural details on the Renwick Gallery - 11, 1 and 2 at the Renwick.

Stories about homes for animals and people read by Emily Eig (pre-school through first grade) - 3 at the Corcoran.

Giant tinkertoys available for play all day in the garden at Decatur House (740 Jackson place NW) and the Octagon House (18th and New York Avenue NW).

Workshops where kids and adults build architectural models with the help of architects - all day at the Octagon House.

Puppet-making workshop at 1 at the Octagon House.

"Archidance" workshop for all ages - 11:15 and 12:00 at the American Institute of Architects building, 1735 New York Avenue NW. CAPTION: Illustration, no caption, By John Pack.