Tiny radio transmitters are giving wildlife biologists some surprising information about the habits of one of northern California's most peculiar and elusive high desert animals, the Department of Fish and Game revealed.

Already in a unique category because of their highly ritualistic mating processes, sage grouse — and their transmitters — are revealing the presence of birds that migrate 40 to 50 miles living with others that never migrate.

The study, according to biologist Frank Hall, is being funded through the construction costs associated with a Sierra Pacific Power Company high-voltage transmission line running from the Alturas area of Modoc County through eastern Lassen County to Reno, Nevada.

Among the principal objectives of the monitoring program is the acquisition of new data about the habitat preferences of sage grouse, including mating sites and nesting sites that the transmission line might impact. The mating sites — also known as strutting grounds or leks — are the historic locations where the male grouse perform mating dances to attract females.

Hall said transmission lines can attract perching predators such as golden eagles that may cause the decline or elimination of the centuries-old strutting grounds and nesting sites. Data collected from the transmitters is helping biologists learn the characteristics of habitats preferred by grouse.

Fish and Game biologists capture the grouse at night, attach the inch-long transmitters and then release the birds for monitoring. They have "collared" a total of 40 birds since the program was launched in the spring of 1998.

Among the most surprising results, Hall said, is the discovery that within a given area there can be birds that are fully resident animals; others that make a 12- to 15-mile migration between summer and winter ranges; still others that complete triangular migrations between winter, summer and mating grounds; and, those that migrate upwards of 55 miles between summer and winter ranges.

"It seems to tell us that the birds have evolved a complex system of distributing themselves in a way that best utilizes available habitats," Hall said.

Also known as sage hens, the western states Great Basin birds are the largest grouse in North America, averaging three to four pounds per female and up to seven pounds per male. The DFG estimates the adult population of grouse in Modoc and Lassen counties at between 3,000 and 4,000 birds.

With life spans considerably longer than most gallinaceous birds and the ability to get by in a water-starved environment, the grouse also are unique because they have no grit-filled gizzards to grind their food. They have a lengthy digestive tract that processes their food.

Sage grouse use sage for a large portion of their diet, but will eat green, leafy vegetation wherever they can get it. They also will feed on grasshoppers, ladybugs and other insects when given the chance.

Hens can produce up to 12 chicks, but are lucky if eight of them are still around six months later. Although they make short, quick flights to dodge predators and hunters, they care capable of rising to high elevations for their long migrations.

California has a two-day, limited quota hunt for sage grouse at the beginning of each September. This year's hunts provided 300 permits for the eastern Lassen County area and 125 for central Lassen.