California condors at the San Diego Zoo, pandas at the National Zoo in Washington, D.C., Siberian tigers at the Minnesota Zoological Garden - three of more than two dozen animal species that are the subjects of a 20th-century version of Noah's Ark.
Sisquoc and Tecuya, condor chicks hatched in San Diego March 30 and April 5, recently replaced Washington's giant pandas, Ling-Ling and Hsing-Hsing, in the spotlight as central characters in attempts to breed declining or endangered species in captivity. Others are waiting in the wings, and already there are several success stories.
The baby condors ''are doing great,'' reports Jeff Jouett, the San Diego Zoological Society biologist in charge of this phase of the Condor Project. ''They're eating like pigs and gaining weight rapidly.''
A third condor egg arrived April 8 at the San Diego Zoo for incubation. Eventually, explains Mr. Jouett, the Condor Project - a joint effort of several zoological and conservation groups as well as state and federal agencies - hopes to have a breeding flock of 16 to 20.
The Los Angeles Zoo has three male condors and hopes soon to obtain a female to breed with one of them - Topa-Topa, who made headlines last year when the supposed mate that was captured for him turned out to be another male.
Reestablishment of species in the wild is the ultimate aim of such captive breeding projects. But in many cases - such as the California condor's - that goal may be decades away, if attainable at all.
The immediate goal, says Jouett, is ''to keep the condor alive as a species for some future time when humans may have gotten their act together'' enough to provide a safe habitat for the majestic vultures.
That's the goal of most such projects, says Nate Flesness, who directs the International Species Inventory System (ISIS) from an office at the Minnesota Zoological Garden near Minneapolis. Mr. Flesness works alongside Tom Foose, who is conservation coordinator for the American Association of Zoological Parks and Aquariums (AAZPA). ISIS is an international data base that helps zoos and other organizations in 12 nations coordinate breeding of endangered species. Flesness points out that since most captive-breeding programs involve small populations of the animals, it is particularly important to protect the gene pool from the bad effects of inbreeding.
Mr. Foose helps zoos prepare and coordinate species survival plans. Since the AAZPA membership is limited to Canada and the United States, he works primarily with institutions in North America. But, according to Flesness, ''cooperation with foreign nations is growing.''
''Coordination is a political challenge,'' Flesness explains, ''because most zoos are local, and it's difficult for local zoo officials to incur expenses not directly beneficial to local patrons.''
Success itself causes some problems. Big cats, especially tigers, have been bred so successfully in captivity that the zoos are running out of space to keep them. This points up one difficulty, says Flesness: In order to preserve the strength and diversity of breeding stock, fairly large populations have to be maintained.
By coordinating widespread programs and providing a central information system, AAZPA and ISIS can help in orderly maintenance of species represented in zoos worldwide.
There are critics, even among conservation organizations, who say efforts should be concentrated on preserving species in the wild. The Sierra Club's condor task force, for example, has warned that the captive breeding program shouldn't be allowed to diminish attempts to restore California condors in their wild habitat.
The view of those who ask, ''What good is a 'wild' animal without a habitat?'' is understandable, says Flesness. But he answers: ''If animals which otherwise would become extinct do survive in captivity, it widens future options and justifies the programs. There could even be future benefits from domestication. No animals have been truly domesticated for hundreds of years, but who knows what may prove possible in the future?''
Further considerations are ''aesthetics, science, and eventual rehabilitation ,'' adds Flesness. ''A living beast such as a Bengal tiger is a beautiful heritage, like a Michelangelo sculpture. Saving them for future generations is worthwhile.''
Flesness points out that disappearance of many species would rob scientists of valuable knowledge. And, like Mr. Jouett in San Diego, he believes that ''within some relatively moderate period we may be able to bring back (their) habitat.''
In recent years three species have been returned to their natural habitats - even though those places may not be as wild as their original homes.
The North American buffalo, rescued by a combination of protection in its habitat and breeding in captivity, is thriving in South Dakota's Black Hills. The European buffalo, which had become extinct on that continent, was successfully bred in captivity and now roams free on a large preserve in Poland. Two years ago, the Arabian oryx (a large, hoofed mammal similar to the antelope) was restored to its original habitat after successful breeding in the Phoenix Zoo. Societal changes - chiefly the wealth oil has brought to Saudi Arabia - have transformed former hunters of the oryx into its protectors, says Flesness.
Approximately 30 species are being bred in captivity now with the aid of AAZPA and ISIS. Flesness says that after these projects are well established, more will be added. Eventually as many as 200 species may be involved, he adds.
John Ogden, director of the National Audubon Society's field work in the California Condor Project, says he is ''extremely pleased with what we're doing in the field.'' Two of the birds have been captured and released with radios attached to them, he reports, and they are ''answering a lot of questions about where condors are and where they are feeding.''
A ''surprising discovery,'' he says, was that a group of four or five ''immature sub-adults'' seem to ''hang out'' during the winter and the nesting season in the Sierra foothills in northern Kern County.
Remote ranches in the area, he says, provide sufficient animal carcasses for the carrion-eating condors to feed on. He sees the possibility that this part of the San Joaquin Valley can become a significant habitat for the California condor, providing the ranches do not give way to more intensive land uses.
Protecting a habitat for the condors to remain in the wild - the present population is estimated at 18 to 20, including four nesting pairs - is his priority, says Mr. Ogden. ''We have to worry about the ranches surviving,'' he admits. ''We've even discussed the possibility of subsidizing them, or perhaps obtaining a tax break for them.''
Ogden says he feels that there is ''fairly broad public support'' for the condor program, which combines work to preserve the species in the wild with captive breeding.
''By and large, captive breeding populations (of wild species) are successful ,'' he says. ''Still, the goal should never be just to have a captive population , but to restore the species to the wild.''