Some of the 17 million birds that vanished from Christmas Island in the Pacific Ocean last fall have returned.

It is believed that the birds originally abandoned the island, leaving nestlings to starve, after unusual ocean currents drove fish away from the area or too deep for the birds to catch.

The sudden population "crash" was the largest ever recorded on a tropical island and one of the few times researchers have observed such an event.

Now, Ralph W. Schreiber, curator of ornithology at the Natural History Museum of Los Angeles County, has revisited the island and has found that some of the 18 species that disappeared are returning. Schreiber estimated that about 100,000 of the 17 million birds are back. The species have returned in proportions vastly different than before, and some have come back in the opposite season from their usual habits.

The birds' disappearance is believed to have been caused by unusual shifts in "El Nino," a complex of winds and currents in the South Pacific. The same phenomenon is blamed for a wide variety of bizarre weather in the past year, ranging from drought in Australia to devastating surfs in California.

In the area of Christmas Island, El Nino created unusually warm ocean surfaces and torrential rains.

The warm water may have sent fish and squid out of the reach of birds, and the rains may have destroyed many of the birds' nests, Schreiber said.

All those that disappeared were sea birds--including terns, frigates, petrels and shearwaters--and all can remain aloft for months at a time. Schreiber said that, while survivors are now returning to their normal nesting places on the island, millions of birds apparently died.

Of the 18 species that vanished last November, three have not returned and half a dozen have returned at less than 5 percent of their normal numbers. Island's Vanishing Birds Back By Philip J. Hilts Washington Post Staff Writer

Some of the 17 million birds that vanished from Christmas Island in the Pacific Ocean last fall have returned.

It is believed that the birds originally abandoned the island, leaving nestlings to starve, after unusual ocean currents drove fish away from the area or too deep for the birds to catch.

The sudden population "crash" was the largest ever recorded on a tropical island and one of the few times researchers have observed such an event.

Now, Ralph W. Schreiber, curator of ornithology at the Natural History Museum of Los Angeles County, has revisited the island and has found that some of the 18 species that disappeared are returning. Schreiber estimated that about 100,000 of the 17 million birds are back. The species have returned in proportions vastly different than before, and some have come back in the opposite season from their usual habits.

The birds' disappearance is believed to have been caused by unusual shifts in "El Nino," a complex of winds and currents in the South Pacific. The same phenomenon is blamed for a wide variety of bizarre weather in the past year, ranging from drought in Australia to devastating surfs in California.

In the area of Christmas Island, El Nino created unusually warm ocean surfaces and torrential rains.

The warm water may have sent fish and squid out of the reach of birds, and the rains may have destroyed many of the birds' nests, Schreiber said.

All those that disappeared were sea birds--including terns, frigates, petrels and shearwaters--and all can remain aloft for months at a time. Schreiber said that, while survivors are now returning to their normal nesting places on the island, millions of birds apparently died.

Of the 18 species that vanished last November, three have not returned and half a dozen have returned at less than 5 percent of their normal numbers.

Schreiber said that such population crashes are probably common over evolutionary time scales.