CALIFORNIA ALBUM : Isolated Island Comes to Life in a Big Way : Thousands of sea lions converge off the Ventura coast for two months of giving birth and fighting for mates.

A two-month fest of birthing, fighting and mating has begun here on one of nature’s great maternity wards, 60 miles off the Ventura coast.

Four thousand California sea lions have already trundled onto fine white-sand beaches to have their pups. By the end of this month, perhaps 20,000 will have given birth.

If June is the month for pups, July is the month for procreation on this isolated, wind-swept western tip of Channel Islands National Park. Mature males, fat from weeks of deep-water foraging, are arriving to scout out the terrain.

By the time they leave, the 1,000-pound males will have lost half their body weight from mating, fighting for that privilege or pining over their losses. Just 10% of males actually mate.

Only in the Arctic regions--and perhaps a stretch of the South African coast--do so many seals and sea lions gather in one place at one time. More than 40,000 of the mammals will clog a two-mile stretch of San Miguel beach by next month, said Robert DeLong, a federal marine biologist who arrived on the island last week.

“It’s absolutely spectacular what has happened out here,” DeLong said.

On a gray afternoon last week, Sharon Melin hid behind a sand dune at Adams Cove on San Miguel’s western tip. Barks and whines from thousands of seals and seal lions just across the sand drowned out the sounds of the sea.

The air had the smell of a huge animal shelter--the odor powerful from a mile away.

“The births are just getting started now,” said Melin, a National Marine Fisheries Service researcher.

Sea lions on the verge of giving birth barked warnings in all directions. New mothers lolled in the warm sand or preened, raising their noses and slowly turning their heads from side to side.

Tiny newborn pups nuzzled and nursed their mothers. Screeching sea gulls swooped in to feed on the afterbirth.

“It gets so much louder as the breeding season comes,” Melin said. “People say: ‘How can you stand this barking?’ But you just don’t hear it--except in the morning. Then it’s the barking and the birds, which is better than waking up to sirens and loud radios.”

Melin, 27, has been coming to the island since 1988. She will spend the summer here, observing and making notes on the activity from camouflaged blinds.

Her work is to follow up on a branding program that began five years ago. Her studies will help determine for the first time what sea lions do for the 16 to 20 years they live.

So far, 1,600 sea lions can be identified by a number on their left shoulders. Each fall, another 500 pups are branded and their numbers entered into a computerized log.

Thirteen of the study’s 200 original pups from 1987 have shown up at San Miguel this summer to have their first babies.

“In the end, I’ll be able to tell what their lives have been like,” Melin said.

About a third of the world’s California sea lions are born on San Miguel. About half of the world’s northern elephant seals are born on the same beaches, but in a cycle that repeats each winter.

Thousands of harbor seals and northern fur seals are also born here each year. The rare Guadalupe fur seal, native to an island off Baja California, drops by for visits.

They come to San Miguel in great numbers because it is safe--isolated from humans and meat-eating predators on shore, DeLong said.

DeLong, 50, has returned here often since 1967 to chart the population of sea lions and four other species of seal that live on the island or migrate here each year.

All species have increased in number under U.S. government protection. Since the 1930s, when 1,000 sea lions were born on San Miguel each year, the number of births increased steadily to 16,000 last summer.

“The thing to remember about this island is that it is unique,” DeLong said.

Melin lives during the summer on a high bluff in a rectangular metal box with small windows that overlook pristine coves and sand dunes covered with ice plant.

Her shed comes with a computer, radio and stove--all solar-powered--and not much else. She bathes in a natural spring not far away and drinks bottled water from the mainland. She has a radio, but no TV.

“I work, eat dinner and go to bed,” Melin said. “. . . I can really focus on what I’m doing.”

DeLong and Melin are also studying the migration and feeding patterns of sea lions, using satellites to track the animals and monitor how deep they dive to feed. Some dive to 1,300 feet.

Melin said she has consciously tried not to identify too closely with her subjects. And she will not give them names.

“You know them,” she said. “But you have to be careful. You don’t want to get attached. They may swim away and never come back.”