Three California condors returned to their nesting areas alone this year, leaving only two breeding pairs of the endangered bird in the wild, the U.S. Fish and Wildlife Service reported yesterday.

A fourth condor apparently also died this winter, according to the service, which noted that one familiar condor is missing although "its mate has apparently formed a new pair bond with a different bird."

The development is ominous for the birds, which numbered 15 in the wild last year, including five breeding pairs. Now it appears that only 11 are left.

Wildlife officials had hoped to augment the condor population through a captive breeding program, taking eggs from the wild to build a captive population. The captive birds would then be used as breeding stock to help repopulate the rugged California canyonland.

Biologists took eight eggs last year, six of which produced healthy chicks. A ninth chick was captured after hatching naturally in the wild. There now are 16 condors in captivity, but federal wildlife officials fear that is too few to support a successful breeding program.

One condor last year died of lead poisoning, apparently the result of a bullet fragment in the carcass of an animal that the bird ate.