RANCHO PALOS VERDES, Calif., March 16— Perched on a cliff peak, teetering in director's chairs with binoculars pressed to windblown faces, a gaggle of out-of-work actors, cinematographers and assorted retirees scans the sea for life signs that have grown faint in recent years.

A dark patch spreads along the surface, a wisp of mist shoots up, a barnacle-studded head breaches the water and a gangly shadow of a whale, barely perceptible in the choppy surf, sticks closely by its side.

''Oh my God, there's another calf!'' exclaimed Alisa Schulman-Janiger of the American Cetacean Society, which has counted gray whales as they commute up and down the California coast for almost 20 years. ''It's so exciting to see a rebound! We're sure due for one.''

After several trying years for the migratory gray whales, when hundreds of calves and their parents washed up dead along the shore -- baffling scientists and dismaying a public that gives them nicknames and tracks their movements -- the beginnings of a recovery are meandering up from Mexico, leaving behind a local tourist economy that just hates to see them go.

''Every time you look around you see spouts, humps, breaching, spy hopping,'' said Maria Mitrani, a tour guide in Ojo de Liebre, Mexico, one of the largest lagoons along the Baja peninsula where cows take shelter from predators and nurse newborns. ''It's good for business.''

On the bluffs south of Los Angeles, spotting whales before they slalom through oil rigs miles off the coast, researchers with telescopes have counted more than three times as many calves in 2002 as they did all last year.

In the calm lagoons in Mexico, naturalists on motorboats have documented roughly twice as many calves as they did in each of the last three years, when the population began tapering off substantially.

''It's nice to see the species recovering,'' said Gabriel Arturo Zaragoza, the census coordinator for the Vizcaíno Biosphere Reserve, where the whales spend the winter.

Though they are heartened by the surge in births, few scientists believed that the population was at risk of extinction. After gray whales came off the endangered species list in 1994, their numbers swelled in three years to 26,600 -- perhaps as many as there had been before whalers began decimating the population in the 19th century.

But right after their record expansion in the mid-1990's, the whales began to die off at one of the fastest rates since commercial whaling was banned in 1947.

Whereas about 35 gray whales typically wash up on the beaches along the Pacific coast every season, as many as 300 each year were rolling in by the turn of the century, leading scientists to believe many hundreds more were dying out at sea and sinking unseen.

Even those that survived looked emaciated, their bones visible through the thick hides that usually cover the layers of blubber so essential for the 11,000-mile annual journey from Alaska to Mexico and back.

Scientists are still trying to account for the whales' sudden deaths, but speculate that a confluence of events prevented them from gorging on amphipods, the tiny shrimplike creatures on which they depend.

Toward the end of the 1990's, warm weather off Alaska made the waters almost bearable to humans, causing what researchers at the National Marine Fisheries Service say was a cataclysmic drop in the food supply.

Around that time unusually expansive ice through the Bering Strait kept whales from reaching their feeding grounds so they could not fatten up for the journey south.

Once they abandon the rich continental shelves in the Bering and Chukchi Seas for the sheltered lagoons of Mexico, the whales essentially do not eat until they return, almost a year later. So after about two seasons of limited feeding, pregnant cows began losing fetuses, and mothers lost the ability to nurse their calves. Many mature whales were too weak to make the whole trip and died along the way.

Researchers have not measured the total impact on the population, but the effect on the youngest whales was clear. By 2000, the number of calves sighted by the fisheries service was less than one-fifth of what it had been three years earlier, causing many to worry about the long-term health of the species.

''This was beyond our control,'' said David Rugh, who heads the gray whale census for the service. ''It was all in the natural course of events.''

For that reason, many scientists see the resurgence of calves as welcome but not permanent. Concerns persist about pollution and the destruction of natural habitats, enough so that the Mexican government canceled plans to build an industrial salt plant near the whales' mating grounds two years ago.

But the primary challenges for the gray whales today are natural occurrences, not humans.

Some scientists speculate that the whales are nearing the limits of what their habitats can support, thus explaining the surge in deaths after the population boom of the late 1990's.

''The numbers are now sensitive to the environment because there are so many gray whales,'' Mr. Rugh said. ''I don't think we can go out there and make things better for them.''

Photos: Whale-watching tours in the channel between Los Angeles and Catalina Island have more to see this year. The rise in the gray whale population has also meant a revival of the Pacific whale-watching industry. (Misha Erwitt for The New York Times); A gray whale breaks the surface of the Ojo de Liebre Lagoon in 1992. (Gerardo Magallon) Chart: ''A CLOSER LOOK: After a Decline, Recovery'' Gray whales travel about 5,000 miles from the Arctic waters to Baja California during the winter to find warmth and to breed. From around January through early April, many of the whales give birth to calves and nurse them in the Ojo de Liebre lagoon in Mexico, where there has been a resurgence in the number of whales. Graph tracks peak number of whales (calves and mature) in Ojo de Liebre. Map of the North America highlighting the gray whale summer feeding areas and route of gray whale migration (Sources: San Luis Obispo County Office of Education; El VizcaÛno Biosphere Reserve)