In the early hours of a Sunday morning, a group of bird-watchers treks through the Patuxent Research Refuge's North Tract. The pickings have gotten slim.

The leafless trees provide few places for their feathered occupants to hide. But after about 90 minutes of sightings--American crows, cardinals, gulls galore--the birders are scanning the treetops with high-powered binoculars to no avail.

Suddenly, group leader Rob Burley stops and, with a raised hand, motions the group behind him to do the same. His eyes dart to one side as he strains to hear better.

He hates that it has come to this, but he purses his lips and uses his secret weapon.

"Pshhhh-pshhh pshhh-pshhh," he says.

"Pshhh-pshhhh pshhh-pshhhh," he continues. "Pshhh-pshhh pshh. . . . "

After he stands silent for a few moments, the sound awaited by Burley is finally heard: The call of the elusive red-breasted nuthatch.

"Do you hear it?" Burley asks. "It sounds like a little toy horn."

Some group members are heartened by the bird's song, but they still can't see it. The rest just shrug and continue marching along the rocky earth trail.

Bird-watching has never purported to be roller-coaster lively. Although the 12,750-acre federally owned wildlife reserve boasts about 250 species of birds, longtime watchers such as Burley know that doesn't translate into nonstop activity.

"That is usually the way it happens during the winter months," says Burley, a volunteer at the North Tract.

"Feast or famine."

Still, the experts say the point of bird-watching isn't the number of sightings. The fun is in enjoying the outdoors: getting a little exercise, taking in the woodsy air. Identifying various species of birds is just a bonus.

"It's being still and letting things happen," Burley says. "It's a lot of sitting and waiting."

Several times a month, the Patuxent Research Refuge sponsors "Bird Walk" and "Bird Tour" programs. On the bird walks, groups of less than a dozen people take guided hikes through the woods. On the bird tours, people file into a 15-seat van for a trip through the park's various habitats, including woodlands, wetlands and meadowlands, and periodically stop to identify birds.

The Patuxent Research Refuge was established in 1936 to support wildlife research and conservation on the land surrounding the Patuxent and Little Patuxent rivers in Prince George's and Anne Arundel counties.

"It's a nice chunk of land," says Steve Noyes, another North Tract volunteer. "When you're flying over it at night, it's a big black area in the middle of a suburban area. To have this amount of forested area that is uninterrupted is amazing."

Noyes recalls one occasion on which the refuge was rife with bird-watchers, more than he had ever seen in his 15 years of bird-watching. When several rare species, including Thayer's, Iceland and glaucous gulls, paid a visit to the park last year, word went out on several bird-watcher's hot lines in Maryland.

Within a few days, dozens of bird-watchers from across the state had flocked to catch a glimpse of them.

"It really created a big scene," Burley says. "The patio area was lined with birders. I have to say, that was one of the big standouts from last year."

On everyday bird hikes, though, bird-watchers should just expect to enjoy the simple pleasures of wildlife. If birds are particularly scarce, Burley says, it helps to use some of the vocalizations that he learned by being out in the field and by listening to recordings.

But "pishing," the technique he used to summon the red-breasted nuthatch, is a last resort. It's essentially the bird's equivalent of a siren, or nails clawing a chalkboard.

"You don't ever want to use that a lot because basically, it's a disturbance. A lot of times birds are curious because they want to see what's making that noise. So they'll poke their heads up so you can get a little peek at them."

Those who embark on bird-watching should take care to avoid startling the creatures, Burley says. "Just your presence is a disturbance," he says.

The next North Tract bird walks are at 9 a.m. Jan. 19 and at 7 a.m. Jan. 23. Free. You must be 16 or older and register in advance. Register from 1-4 p.m. Tuesday through Thursday. Call 301-497-5887.

CAPTION: Canada geese gather near the Patuxent River.

CAPTION: Experts say the point of bird-watching isn't the number of sightings, but enjoying the outdoors and getting some exercise and fresh air. Above, Canada geese glide.