トキのひな誕生 野生に定着する道のりは長い

The Yomiuri Shimbun 8:30 pm, May 10, 2014
Long road ahead before ibises are well established in the wild
トキのひな誕生　野生に定着する道のりは長い

A baby bird was born to a pair of wild crested ibises on Sado Island, Niigata Prefecture. This event advances the

project to return the crested ibis to the wild into a new phase.
　新潟県の佐渡島で、野生のトキにひなが誕生した。トキの野生復帰へ、新たな段階に入った。

The chick is the first member of a third generation of ibises since birds bred in captivity began to be released on the

island in 2008. Its parents are crested ibises living in the wild; its father was born in the wild on the island in 2012.
　ひなは、人工繁殖を経て、２００８年以降、島内に放鳥されたトキから数えて３世代目にあたる。親鳥は、１２年に佐渡の自然界で

生まれた野生のトキだ。

“The innate strength found in wild birds has been reawakened in the birth of an ibis,” said an Environment Ministry

official. We sincerely hope the chick will grow up to safely leave the nest.
　環境省は「トキが本来持っている野生としてのたくましさが引き出された」とみている。ぜひ無事に巣立ってほしい。

Crested ibises once lived in many places across the country, but their numbers declined sharply after the Meiji era

(1868-1912) due to the deterioration of their habitat and other factors. Japan’s native population of crested ibises

went extinct in 2003. In 1999, the Environment Ministry began a breeding program using five crested ibises given by

China to release the birds into the wild.
　トキはかつて日本各地に生息していたが、生息環境の悪化などで明治以降、激減した。日本生まれのトキは０３年に絶滅した。
　環境省は、トキを野生に復帰させるため、中国から１９９９年以降に贈られた５羽をもとに、人工繁殖と放鳥を続けている。

Today, about 100 crested ibises live in forests on the island. More than 10 years since their domestic extinction in the

wild, it is a joy to see them returning to Japanese skies.
　現在は約１００羽が島内の森林に生息する。絶滅から１０年余を経て、日本の空にトキが戻りつつあることは喜ばしい。

However, the progress in the project to return crested ibises to the wild has also highlighted problems with artificial

breeding.
　野生復帰事業の進展とともに、繁殖の課題も見えてきた。

It has been observed that parent birds raised in artificial breeding environments and released into the wild often do

not brood their eggs or feed their babies. Many of the eggs they lay are unfertilized and never hatch.
　人工繁殖で育ち、野生に放たれた親鳥は、抱卵や給餌を放棄する例が目立つ。卵を産んでも、孵化ふかしない無精卵が多い。

Last year, 24 mated pairs of crested ibises built nests, but only two of them saw offspring successfully leave the nest.
　昨年は自然界で２４組が巣作りをしたが、ひなが巣立ったのは２組にとどまった。

Solutions to problems

Researchers are finding that hatching the eggs of crested ibis to be released into the wild without the use of artificial

incubators and allowing their parents to feed them while they are still at a rearing facility are effective solutions to

such problems.
　こうした問題を克服するには、放鳥するトキに対し、施設内飼育の段階から、孵化器を使わず、給餌も親鳥に任せるのが有効である

ことが分かってきた。

We hope researchers will deepen their expertise on the biology of the crested ibis so that the birds can be bred and

raised to leave the nest more smoothly.
　繁殖、巣立ちが順調に進むよう、トキの生態について、さらに研究を深めてもらいたい。

The negative effects of inbreeding are also a concern. Last year, four chicks born to a mated pair of sibling birds

were caught to be kept at a rearing facility. They were separated, as it is feared that the reproductive ability and

immunity of the species as a whole could be weakened unless genetic diversity is secured.
　近親交配の影響も懸念される。昨年、兄妹ペアから生まれたひな４羽は飼育施設に隔離された。遺伝的な多様性が確保されないと

、島のトキ全体の繁殖力や免疫力が弱くなる恐れがあるからだ。

Efforts should be made to diversify the blood lines of the birds.
　血統を増やす取り組みが求められるだろう。

The Environment Ministry spends ¥150 million every year on the project to return crested ibises to the wild. The

project aims to realize a constant population increase without releasing artificially bred birds to the wild. But it is not

clear when the final goal can be achieved.
　環境省は、トキの野生復帰事業に毎年約１億５０００万円を投じている。放鳥せずに野生のトキが増え続けることが最終的な目標だ

が、その時期は見通せない。

Reviving an extinct species requires a great deal of time and money. The long road to resettling the crested ibis in

the wild is evidence of that.
　絶滅した種を復活させるには、膨大な時間とコストがかかる。トキが野生に定着するまでの長い道のりが、それを示している。

Sado Island residents are helping crested ibis survive in the wild. For instance, they keep water in rice paddies even

during winter to help the birds catch prey such as loaches and frogs. They also moderate their use of chemical

fertilizer and pesticide in rice cultivation.
　佐渡島では、地元住民らがトキの手助けをしている。餌のドジョウやカエルが取りやすいように、冬でも水田に水を張る。化学肥料や

農薬を抑えた米を作る――。

Efforts to coexist with the crested ibis will lead to conservation of the rich natural environment on the island.
　トキとの共生を目指す試みは、島の豊かな自然環境を保全することにつながるだろう。

(From The Yomiuri Shimbun, May 10, 2014)