CALIPATRIA, Calif. (AP) _ Lifeless nests and skeletons covered in feathers littered the rocky shore of a barren Salton Sea island Thursday, confirming the return of the season of death.

The northeast side of Mullet Island _ where the Salton Sea's largest and most promising colony of double-crested cormorants once nested _ held only rotting carcasses, unhatched eggs and flies.

``We normally have some deaths, but when there are full clutches of dead birds, there's something wrong,'' said Ken Sturm, biologist for the Salton Sea National Wildlife Refuge. ``Obviously something bad happened here.''

After last summer's epidemic of avian botulism that felled more than 14,000 birds representing 69 species, including endangered brown pelicans, biologists had expected similar problems this year at California's largest lake.

``There was no change in the ecology of the sea,'' said refuge manager Clark Bloom. ``We felt it was just a matter of time before this happened.''

But nobody thought death would return so soon.

By Wednesday, biologists counted at least 1,700 dead cormorants that were last seen alive and nesting on Mullet Island in early March. The birds' black feathers now sharply contrast against the island's white rocks.

``It's kind of like a Hiroshima scene,'' Sturm said.

The odor of decomposing birds overpowers the sea's rotten-egg stench. In 100-degree heat, flies stick to visitors who must wear rubber boots and remove them before returning to the dock to prevent the spread of disease.

The cormorants are a small part of the problem. About 2,000 birds from 38 species have also been found dead on the sea's shore.

Also, two massive fish kills left 60,000 tilapia bobbing in the water and rotting on the shores.

An incinerator burns the bird remains to prevent disease from spreading. A makeshift hospital is being built to stabilize sick birds before they are sent to rehabilitation centers.

So far, only four brown pelicans have died. But thousands more are expected to fly in over the next two months from Baja California and the Sea of Cortez, where they spend winter.

Tests to find out what killed the cormorants have not been finished, but some of the birds showed signs of avian botulism, which targets the birds' nervous system and leads to torturous deaths.

Even if avian botulism is determined to be the culprit, it does not explain how the bacteria is spread in the manmade sea's unusual ecosystem or what role the sea's pollution plays in the deaths.

The salty lake has become a favorite spot for birds on the Pacific Flyway as development elsewhere in California has destroyed natural wetlands. Formed by an accidental break in the Colorado River in the early 1900s, it now covers 380 square miles across Riverside and Imperial counties.

Today, it is fed only by agricultural runoff and polluted water from the New and Alamo rivers. Because water escapes only through evaporation, its salts and pollutants concentrate over time. It is now 30 percent saltier than the Pacific Ocean.

Plans developed last year to control the salinity by building massive dikes still need to be studied, Bloom said. It will be another three or four years before the environmental report is completed.