Hire a bird guy to run a zoo, and soon you have more feathers in the collection.

The bird guy in this case is Dave Orndorff, the Mill Mountain Zoo's executive director since December. And the feathers, which are still arriving as the Roanoke zoo prepares for a busy summer season, belong to an international flock of birds, large and small.

The biggest are Ivan and Kana, a pair of Asian black vultures, who each have a wingspan of close to 10 feet. The birds are not on exhibit yet, but earlier this week a zookeeper ushered two curious visitors to an off-site cage for an early peek. Kana came hopping over.

"They would be the top bird at any carcass," explained the keeper, Kelly Prim, as she offered Kana a small stick. The bird's hooked beak snatched the twig. Prim added, "We do interact with them, obviously not with our fingers."

The residents of the zoo's new interactive aviary, set to open this summer, will be smaller and less menacing.

These include 26 varieties new to the zoo. There are scarlet ibises, a native of South America that resembles a small flamingo. A pair of blue-bellied rollers, acrobatic fliers from Africa. And superb fruit-doves, colorful birds found in Southeast Asia.

There are nonflying additions to the zoo's collection, too. Two baby porcupines were born to the zoo's mating pair earlier this spring. Red wolves have replaced the red kangaroos. Though wallabies, or smaller kangaroos, should be added soon, too.

And a new Zoo Choo, the tiny red train that circles the menagerie, started carrying passengers this month.

Mill Mountain Zoo is going through a growth period, Orndorff said, energized by a successful national accreditation review last fall.

Two years ago, the zoo's future was less certain. It failed the 2006 accreditation review because of concerns about its facilities and financial stability. Also that year, a Japanese macaque, Oops, escaped for a week and the zoo lost its longtime mascot, Ruby the tiger, to health problems.

But local donors and fundraising efforts have brought in close to $500,000 since then, estimated Sara Brooks, president of the Mill Mountain Zoological Society. The zoo has also matched the first two installments of a three-year Roanoke city challenge grant worth $500,000, she said.

And then there are the animals. Nine exhibits will open this year, more than have opened over the past four years, Orndorff said. The zoo has also been an active part of national conservation programs that help to sustain rarer breeds.

"We're a tiny, little zoo on the top of a mountain," Brooks, with the board, said and chuckled. But considering the recent upswing, she added, "I think the zoo is transitioning very nicely."