NIIGATA (Kyodo) Of the eight crested ibises confirmed to have survived their release into the wild last year, all four females are now on Honshu, while the four males opted to remain on Sado Island, the Environment Ministry said Saturday.

As a result, it is unlikely that the birds will breed this spring, the ministry's local office said.

The fourth female was found Saturday morning in a rice paddy in Niigata after having been confirmed on Sado Island on Friday afternoon.

The Niigata Prefectural Government and Sado city asked the ministry to catch the females and bring them back to the island, but the ministry rejected the request and said it would only catch them if they are in trouble.

Crested ibises were returned to the wild for the first time in 27 years in September, with 10 artificially bred birds — five males and five females — released on Sado.

Of the 10, eight — four males and four females — were confirmed alive and well.

One female was found dead in December and the whereabouts of the remaining bird are unknown.

The crested ibis (Nipponia Nippon), used to inhabit extensive areas of East Asia, but was almost wiped out by hunting and environmental disruption. The bird is now found only in Japan and China.

The crested ibis, or "toki" in Japanese, was designated a national natural treasure in Japan in 1952.

Wild crested ibises were virtually extinct in Japan by January 1981, when the Environment Agency, the predecessor of the Environment Ministry, captured the last five for artificial breeding purposes.

The last ibis born in the wild in Japan, named Kin, died in 2003. But the number of artificially-raised ibises in Japan has risen to 120 after China provided some to help Japan artificially breed the protected bird.