If N.Y. Owls Can Make It Here . . .

Drawing puzzled stares from joggers and bicycle riders, the small band of trackers moved through Central Park, aiming a radio antenna at the shadowy outlines of trees silhouetted against the night sky.

Depending on whether the signal from the receiver they carried faded or grew stronger, they darted up hills slippery with a carpet of fallen leaves, moved through underbrush and crossed a small stream. Occasionally they peered with a night vision scope.

Their mission: trace a flock of increasingly savvy screech owls.

Why, you ask?

Therein lies a tale of nature and nurture.

In the 1920s, the owls were one of 10 species of breeding birds in Central Park. By the 1960s, they had slowly disappeared.

No one is sure of the reason. The two most prominent theories are that pesticides may have harmed the birds and killed the rodents and insects serving as their primary sources of food, or that they have suffered from the removal of older dying trees containing cavities where the owls nest.

In 1998, conservationists released six screech owls in the park with the hope they would thrive. One died, another remains. Whether the other four birds perished or flew the coop remains a mystery.

This year, with the aid of sophisticated technology, the New York Parks Department in partnership with Fordham University’s Louis Calder Ecology Center decided to try again on a much larger scale. The hope is screech owls, which are not a migratory species, will breed and develop their own sustainable presence.

“It’s bringing the park back to its original natural heritage,” said Henry J. Stern, New York’s parks commissioner, who has served under both Mayors Rudolph W. Giuliani and Edward I. Koch.

The project is part of a larger effort to restock New York’s numerous parks with birds, other animals and plants. Since 1997, a number of species have been introduced, including luna moths, quail, prickly pear cactuses, painted turtles, American chestnut trees, spring peeper tree toads, woodchucks and monarch butterflies.

“I wanted to be a man for all species,” Stern said. “I have always had an interest in plant and animal life. You don’t have to invent imaginary extraterrestrial creatures. You can have all the excitement you want from species that exist on Earth.”

After careful preparation, which included weighing each bird and determining that food sources were sufficient, 11 female and seven male Eastern screech owls--found abandoned as babies and raised at four wildlife rescue centers--were set free in Central Park.

All but one of the owls--which was too small--was fitted with a radio transmitter enclosed in a tiny strap-on backpack.

“Each transmitter is on a specific frequency,” said William Giuliano, an assistant professor and wildlife ecologist at Fordham. “We can tell which bird is giving off the signal and we can home in to the bird. We locate them several times a week to see if they are still alive.”

In addition to assessing the health of the owls, the ecologists use the radios to plot their positions and movement patterns in the park.

“The owls are nocturnal. They sit on a roost during the day resting, particularly midday,” Giuliano said. “At night, the birds forage for food.”

Manhattan’s Central Park is a fertile wildlife habitat. Raccoons, opossums, squirrels, reptiles and more than 80 species of birds inhabit its 843 acres. During migrations, almost 200 different kinds of birds can be counted.

On a recent night, Giuliano and a small group of park rangers tracked the owls. Their mission not only was to identify where several were situated, but to change a weak battery in the transmitter one of the birds carried.

Finding the owls can be tricky. Interference and the park’s landscape can block beeping from the birds. If an owl is on the ground behind a big rock or in a hole in a tree, the radio signal can be stifled. Sometimes, instead of hearing the birds, trackers find themselves listening to nearby pilots calling air traffic controllers.

After an unsuccessful search at the northern end of the park, the group followed a steady stream of strong transmissions to the south. Near Fifth Avenue, an owl sat alertly in the notch of a tree branch.

Suddenly, scurrying was heard in nearby underbrush. The owl darted down and disappeared from view as it searched for food.

In an act of renewal in a time of tragedy, two of the owls were set free to live in the park six days after the Sept. 11 attack on the World Trade Center.

“They stayed in their box for a while, sort of checked out the scene, moved out toward the edge of the box, and then they both flew off,” said Christopher Nagy, a research associate at the Calder ecology center, who was one of the trackers and who witnessed the release. “It was a great first feeling of a little hopefulness.”