With loud rock 'n' roll echoing across the desert and bright lights groping in the dark, wildlife biologists roam Shoshone Basin working on their night moves.

Bouncing over rocks and sagebrush, just a few miles north of the Nevada border, an Idaho Fish and Game Department biologist and three helpers search the midnight desert for sage grouse. The birds are netted, fitted with small radio transmitters and leg bands and released. It's part of a study to learn more about their habits.The department hopes that learning where they nest, raise their young, spend the winter and what they prefer to eat will result in better land use decisions, and, ultimately, more birds.

The music, apparently, covers the noise of the approaching night stalkers, keeping the birds from flushing.

"Led Zeppelin seems to make them sit better," said graduate student Tom Maeder. But he's also had good luck with Bob Seger's "Night Moves." As Seger wails from the loudspeaker lashed with baling wire to the grill, the four-wheel-drive Fish and Game pickup truck, whining in low-range, crashes through the sagebrush. Region 4 biologist Randy Smith is at the wheel.

Rich Holman, a Region 4 conservation officer pressed into late-night duty, peers through the Fish and Game's own version of night-vision glasses - a spotlight in one hand and binoculars in the other.

Two men ride on the frosty tailgate, armed with nets on four-foot poles, like large fish-landing nets. Holman probes the sagebrush for the tell-tale greenish glint of light reflecting from a sage grouse retina. On a frosty night, however, Holman often is fooled by reflections from ice crystals on sagebrush leaves.

The first few sage grouse turn out to be bushes, shadows and rocks. But his eyes soon adjust. He spots what he thinks is a sage grouse, invisible to the others, and signals the driver, who steers toward the lighted spot.

The net-men jump off the tailgate and stumble, nets in hand, in the dark alongside the truck. The spotter, standing upright in the bouncing pickup bed, tries to keep the bright light on the hunkering bird. Smith turns up the music. The truck stops when it is within about 30 feet of the bird.

The lead net-man, Maeder, rushes forward, oblivious of the rocks and brush trying their best to trip him. He slaps the round net over the bewildered bird, transfixed in the spotlight.

Maeder, a 26-year-old graduate student from the University of Montana, gently cradles the frightened bird to keep it from struggling. The bird, a female, is carefully freed from the net.

Dark brown eyes blink in the glaring spotlight, as nimble fingers affix a numbered, metal band to one leg and a radio transmitter - like a tiny backpack - on its back. Smith, Maeder and Holman note the transmitter frequency, the band number and the bird's sex and age. Moments after it was captured, the bird is released.

Smith follows it with the spotlight to make sure the radio doesn't hamper its flight. If the radio is improperly attached, the bird is recaptured and the radio reattached or just removed.

With the equipment back in the truck, the merry chase begins anew.

So far this year, Smith and his helpers have captured 20 sage grouse in Shoshone Basin. With weekly checks continuing until the nesting season ends in about a month, Smith will follow each bird from the ground and from an airplane, periodically noting its location.

He will continue to keep tabs on them once a month, for about a year or 18 months, until the radio stops transmitting or until the bird dies.

The information from the tagged and tracked birds, combined with records from hunter check stations in the basin over the past 25 years, will help Smith advise the Bureau of Land Management in locating planned burns to control sagebrush.

Sage grouse are intimately tied to their aromatic namesake. Some sage grouse migrate a lot, some a little, others hardly at all, Smith said. But they are picky eaters. They favor certain strains of sagebrush, sometimes even individual plants, for food.

"The birds don't nest in crested wheat," Smith said. They nest under sagebrush. In the past, the Bureau of Land Management and the Forest Service have burned off large tracts of sagebrush and seeded crested wheat grass for livestock forage. But indiscriminate sagebrush eradication can threaten vital grouse habitat, Smith said.

Severe winter weather, wet weather during the nesting season and predators all take their toll from year to year. But in the long term, habitat loss to fire or other sagebrush eradication plays a more important role.