With an owl, a vulture and a flock of flamingos flapping around as props, National Aviary officials yesterday unveiled an ambitious $23 million expansion and renovation project that will keep birds of wildly different feathers flocking together on Pittsburgh's North Side.

The project includes a new, open air, rooftop theater for bird-of-prey programs, expanded exhibit and classroom space, and an indoor theater for free flight bird shows. It aims to revitalize the 56-year-old aviary by improving interactive programming and visitor amenities and establishing a stronger connection to Allegheny Commons and West Park.

"Through this new theater experience, visitors will see, hear and feel the presence of birds, nature's most colorful and dynamic representatives, furthering the National Aviary's goal to inspire positive and respectful connections to nature among educators, students and visitors," said Mike Flinn, aviary board chairman.

About 100 birds will be added to the aviary's permanent population. The major makeover also includes a new public cafe, classrooms, exhibits and a two-story atrium entrance facing Arch Street and designed to improve accessibility for school groups, tours and individuals. Much of the new space will be in two curved wings added to the existing structure.

The new indoor "Flitezone Theater" will have high definition video screens and moveable stages for the bird shows.

"Our theater is all about creating a better future for the community and creating many more zealous stewards for our natural world," said Linda A. Dickerson, aviary president and chief executive officer.

"It's one thing to tell a class that vulture populations in India have declined by 90 percent, and that extinction could occur within the next decade. [But] pair that information with a live vulture flying inches overhead against footage of vultures in the wild, and you hopefully will inspire a lasting love for nature and perhaps even a commitment to protect these magnificent creatures for future generations."

"The new building creates an iconic front and welcoming front door that reflects its function as a building that houses and celebrates birds and the nature of birds," said Paul Rosenblatt, principal of SPRINGBOARD Design, which is overseeing the project. "Overall, our goal is to create a more experiential environment, one that stimulates visitors' imaginations about birds, nature and the world around us."

The aviary has raised $16.9 million for the project from the Richard King Mellon Foundation, Eden Hall Foundation, Heinz Endowments, Colcom Foundation, Hillman Foundation, several anonymous foundations and the state. A public fundraising drive will be launched soon, Ms. Dickerson said, and additional money will be requested from the state.

Design plans will be submitted to the city's Historic Review Commission next Wednesday and the city Art Commission on Nov. 21. If the commissions approve, construction will begin in the spring and the project will be completed in June 2010.

The aviary will remain open during construction.

Ms. Dickerson said she expects the new facility will increase attendance by at least 20 percent and maybe up to 40 percent. Attendance was 125,000 last year and is running about 6 percent higher this year so far.