The Jalak Balis are going home. Last Friday 20 pairs of the exotic Balinese birds, bred in 11 American zoos, left Los Angeles for the Indonesian island on which they have nearly become extinct.

The birds, also called Bali mynahs, are snow white except for black wing tips, bright blue skin around the eyes and dark legs. Because of their beauty, they became popular in zoos. But because they did not breed in captivity, new ones had to be captured to replace those that died. In the meantime, agricultural expansion on Bali wiped out much of their habitat.

By the 1970s, when the Jalak Bali was declared an endangered species, zoo keepers discovered that if they fed the birds with the kinds of insects and fruits that closely matched their natural diet and provided more appropriate living quarters, the birds would breed.

At about the same time, Guy Greenwell, then curator of birds at the National Zoo, developed a registry to keep track of pedigrees and encourage crossbreeding among zoos. This minimized the deleterious effects of inbreeding.

When it was discovered that Bali's wild population was down to about 60 birds, the breeding programs of 11 American zoos were coordinated to produce more birds than the zoos needed. Starting a week ago, 10 zoos shipped a few pairs each to the Los Angeles zoo. From there, they went to a zoo in Surabaja, Indonesia to start a new breeding colony. The colony's offspring will be released in Bali's one national park, the only refuge of the Jalak Bali, starting next year.