Preliminary Research on Releasing Program of the Crested Ibis (Nipponia nippon)トキ(Nipponia nippon)の野生復帰プログラムに関する予備研究

Authors著者名

XI Yongmei席 咏梅¹⁾, LU Baozhong路 宝忠¹⁾, FU Wenkai傳 文凱²⁾, SU Yunshan蘇 雲山³⁾

Summary要約

The present study was designed to try a possible release to the wild of the captive-bred Crested Ibis (Nipponia nippon). A special attention was paid on preliminary research about reproduction behavior of the endangered Crested Ibis. In breeding season, the Crested Ibis incubated eggs and feed their chicks in turn by male and female in the wild. In the case of captivated birds, they lay eggs and incubate them in turn in the early incubation period, but in captivity, the parents tended to kill the chicks during hatching not post hatching. In the present research project, therefore, we tried to introduce the hand-reared Crested Ibis to a kind of nature condition using parents and chicks which were previously raised by hand rearing in the Yangxian center. Wide range of flight cage was used for one pair to be visually isolated from the others, leading to the results of successful parental care of the Crested Ibis in the captivity. We critically evaluate the usefulness of this preliminary research on reproduction as part of reintroduction of this species, suggesting the possible propagation post-release of the captive-bred Crested Ibis.

Key words： Crested Ibis, reproduction, release

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本研究の目的は、飼育下繁殖によるトキを野生復帰させる道を探ることにある。絶滅に瀕するトキの繁殖行動についての予備研究を特に重視した。野生の状態では、繁殖期にはトキは雄雌交代で抱卵し、雛に餌を与えている。飼育下の場合、産卵後、抱卵初期には交代で抱卵するが、孵化後ではなく孵化の過程において雛を殺してしまう傾向のあることが観察されている。

本研究では、それ故、洋県トキ救護飼育センターで人工飼育された親鳥と雛を用いて、人工飼育で育てたトキを自然に近い状態に置いて観察する実験を行った。繁殖ペアを他のトキから見えない、飛翔可能な大きさのケージに入れて飼育した結果、飼育下に置かれたこのペアのトキは十分な抱卵と育雛行動を行ったのである。

トキ種の生息に適した地域への再導入の一部としての繁殖行動に関するこの予備研究は、飼育下繁殖によるトキの野生復帰後の繁殖の可能性を示している。我々は、注意深く本研究の有効性を評価していかねばならない。

（推薦者：河合 明宣　訳）

INDEX

• 1. Introduction
• 2. Materials and the Method
• 3. Results
• 4. Discussion
• 5. Acknowledgments
• 6. Reference

1. Introduction

The Crested Ibis was formerly found from the Russian Far East south through the Koreas and Japan to central China. It has been declining dramatically since the early part of 20^th century. By the late 1970s, it was extinct in Russia and Korea (Yamashina, 1977； Archibald, 1981). The last five birds in Japan were captured for possible captive breeding in 1981 (Yamashina, 1983； Ishii, 1999). However, a single Japanese Crested Ibis survived until one pair loaned from China successfully bred at the Sado Ibis Conservation Center in 1999 (Chikatsuji, 1999； Fujihara and Xi, 2000 a,b).

In China, the Crested Ibis (Nipponia nippon) had declined to only seven birds, including two breeding pairs and three nestling by 1981 (Liu, 1981). Since then, a conservation project, which has included management of the free-living ibis population and a sort of basic researches, started from the seven ibises (Liu, 1981； Lu et al., 1986 & 1999； Shi, 1990 & 1992； Tan, 1989； Xi and Fujihara, 2000 a,b). Some of the scientific researches have been conducted using accidentally died birds (Fan et al., 2000； Liu et al., 1995； Liu et al., 1999； Xi et al., 1999； Yan et al., 1999). With regard to this bird, the 1^st International Symposium on this species has been held at Hanzhong, China in 1999. In which most of the researches on the Crested Ibis and some other related endangered birds were discussed from the points of future prospects of this kind of wildlife (Cao et al., 1999； Coulter, 1999； Li et al., 1999； Wang, 1992； Xi et al., 1999； Zheng, 1999). Some of the scientific researches on field observation about the ibis, including general reviews of ibis have also been reported (Cao et al., 1994； Fan et al., 1990； Fujihara and Xi, 2000 a,b； Su et al., 1999； Lu et al., 1999； Liu, 1999； Ma et al., 1999； Toshio Torii, 1999； Wang, 1999； Yu, 1991； Yoshio, 1999； Zhang et al., 1999； Zhai, et al., 1999).

On the other hand, captive-breeding has been difficult and first successfully achieved in 1989, with two chicks survived to one week in Beijing Zoo (Li, 1991). Another captive population began to be established in Yangxian Ibis Breeding Center in 1990 by rescuing few sick and injured chicks and abounded eggs in the wild (Xi et al., 1993； Xi et al., 1997). The birds successfully bred since 1995, thereafter some progeny also joined breeding (Xi et al., 1999).

Hitherto, captive rearing of species with release to the wild has been being am important management technique used in attempts to save species from extinction (Sccott et al., 1987). Some of endangered birds have succeeded, such as Whooping Crane Grusamericana (Bender, 1992), California Condor Gymnogyps californianus (Kuehler, 1988； Bender, 1993), Hawaiian Goose Branta sandvicensis (Black, 1994) and Bald Eagle Haliaeetus leucocephalus (Simons, 1988) in United States； Bald Ibis Geronticus eremita in Turkey (Akcakaya, 1990； Cade, 1994), and especially Mauritius Kestrel Falco punctatus in Mauritius, have been increased from four known birds in 1974 to more than 331 individuals by 1994 (Jones, 1994), suggesting the possibility of rearing the endangered birds by human being in the captivity, though hard task has needed to be successful even some failed and / or are still trying to help threatened species (Clout et al., 1994； Cade et al., 1994； Holt, et al., 1996； Richand et al., 1999； Brownell, 2000).

Therefor, to establish captive population with an intention of reintroduction has been a long term considerable attempts for saving the Crested Ibis in Japan and China. Three captive populations have been built respectively with a number of 7 individuals in Sado Ibis Conservation Center in Japan, 21 individuals in Beijing Zoo and 106 individuals in Yangxian Ibis Breeding Center, resulting of 134 individuals in total. However, of 112 individuals were raised by hand rearing since the abnormality of parental care occurred in captive breeding of the Crested Ibis. It showed that the parents attend to kill the chicks during hatching. It seemed a sign of disadvantages for reintroduction in the future.

In the present research project, we conducted the reasons of this abnormality, focusing on the primary study of reintroduction. It was achieved by reestablished a new cage for one pair to be visually isolated from the others. Fortunately, one chick was successfully produced by parental incubation and care, has fledged. As the result, that the probability of the parental birds loosing the ability of parental care in captivity was rejected. The occurrences of abnormality were because of environment pressure in relatively smaller aviaries. It is indicator of the first step for hopefully reintroduction of the birds in the near future.

2. Materials and the Method

In order to leading the parental incubation and rearing, a large aviary with facility for reproduction was built in the woods in side the breeding center in November 1999 (Fig.1, Fig.2) This aviary was about 80 square meters, located in the middle of the hill. It is 50 meters far from the other breeding cages of the center so as to prevent the birds contacting with other breeding birds. The slope of the hill was used to be the ground of the cage instead of the flat ground. Outside the surrounding of the cage have many pine trees, oak and cypress. This circumstance access the naturally habitat of the wild Crested Ibis. We used the nylon net to be the fence of the cage in stead of iron net which were used for the breeding cages before (Fig.3) in order to avoid crashing and accident happening. Some branches were arranged on the top of a pine tree inside the cage to be supposed the site of the nest instead of the man－made basket (Fig.4), which were used to be the nest before. A small concrete pond was also provided in the cage for drinking water, eating loach and bathing. A set of TV monitory system, which was facing the nest, was set up at the corner of cage for observing any kinds of breeding activities and reproductive behavior.

After preparation the facility for reproduction, first breeding pair was introduced to this new cage on 3 January, 2000. The male was born in 1996 by captive－bred, with red ring on the left leg and black ring on the right leg. The female was also born in the center in 1996, with blue ring on the left leg and black ring on the right leg. The fresh loach and artificial diets were provided for them (Table 1). Some branches and dried grass were placed on the ground to help the birds building nest. The pair was kept in this condition only for one month without getting any sort of breeding acting and reproductive behavior. Therefor, we moved out this pair, and another new pair was introduced again on 3 February 2000. The male of this pair was two years old and the female was three years old. They are also captive bred in Yangxian center in 1998 and 1997, respectively.

3. Results

After half a month of setting the second pair in the new cage, the pair started displaying flying together (Fig.5), nacking each other and finally copulating on 17 March 2000 (Fig.6).

To stimulate the behavior of nesting, some of nesting materials was put in the nest site of the pine tree. However, the birds threw the branches, which were introduced in the nest, away. After that they started picking up the materials from the ground to build the nest by themselves on 22^nd of March. In this case, usually, the male took participation in bring the materials to nest and the female prepare and arranged the nest. Sometimes, the female tried to sitting on the nest for a short time. Approximately two days after this appearance of the behavior, the female started laying eggs. The first egg was laid on 29^th of March. Since then fresh mealworms were given to the birds on the basis of 100 gram per day. Until 3^rd of April 3 eggs were laid, they incubated the eggs themselves in turn. During incubation period, one egg accidentally was broken in the nest on 25^th of April, and another egg on 30^th of April. The last one was taken out for checking the fertility because that, judging by the incubation period, this one should be hatching 4^th of April. It was found this egg was infertile.

Following this treatment, another fertile egg, which was laid by the other breeding pair and just during piping stage, was introduced in the nest to test further incubation by the parental birds. Unfortunately, the pair threw this egg away during its hatching. This series of reproduction was finished for the first clutch. Following this happening, new nestling materials were prepared for the second clutch. Then on 16^th of May, they started relaying and two eggs were laid (Fig.7). The parental birds incubated in turn, during this incubation period, one egg was damaged again on 26^th of May, but finally, the last egg hatched on 13^th of June. This series of events was monitored by TV set； unfortunately, the last chance of the chick hatching was missed by TV monitory due that the trouble happened to the facilities. However, the voice of the chick was heard by our stuff (Fig.8).

14^th of June, it was found that the parental birds take care of the chick to feed the first time. The male and female fed the chicks in turn, with about 20 times in total a day.

21^st of June, at day 8 the chick’s bill was found to grow a slightly long, and the behavior of bugging food from the parental birds was observed.

22^nd of June, parental bird protected the chick by making a shedder with their body and feather since sunshine was exceptionally hot at that time.

23^rd of June, when it was raining, the parental bird displayed the same behavior as mentioned for strong sunshine previously.

As the chick grew up, gradually increased amount of mealworms were given, together with some kinds of vitamins and artificial diet.

27^th of June, the chick was observed grown up to about 800 gram of body weight, displayed moving and standing up for a short time, Since 4^th of July, the male and female of parental birds tried to leave for taking food together, leving the chick alone in the nest. After spending several minutes outside the nest, the male or female returned to the nest to feed the chick .

17^th of July, the chick with plumed feather could stand on the edge of the nest, showing the practice of flying.

25^th of July, the chick tried to fly down on－to the ground to follow the parental birds for feeding (Fig.9). Sometimes, the chick couldn’t eat the fresh loach, thus the parents fed the chick again. About 3 days after this behavior, the chick could go and back between the nest and ground to get food freely (Fig.10).

4. Discussion

This experiment is the first to indicate the possibility of parental incubation and rearing, so far the 10 chicks had been killed by the parents during hatching in the previous experiments.

The parental birds killed the hatchlings was occurred in Yangxian center (Xi et al., 1999) also in Beijing Zoo (Li, 1992). We had ever analyzed the reason for it. Two aspect factor probability presented for the Crested Ibises. One is because of incomplete ability of parental care since they were all taken cared by hand rearing. If so it would be fail with the reintroduction program, because that there would not be present propagation when the captive individuals are released to the nature. Another reason is because that limitation of cages size and crowding of vicinity closed breeding cages caused the environment pressure for birds. But carrying out the present experiment rejected the former reason.

As we mentioned the size of cage the former breeding cages were very small in size and very close to each other, this probably induce a kind of stress for the breeding birds. In this experiments wild range of flight cage was used. And this pair couldn’t see the other breeding pairs in the center. This experiment was informative for successful parental care in captivity due to environment changes. It suggested that we have to build the breeding cages separately in the future in order to train the offspring for preparing the further reintroduction program.

As W. Conway noted, propagating birds in captivity has the potential to accomplish three main goals： (1) providing a ”gene bank” to preserve the unique genetic information of species that have become greatly reduced in number or have disappeared in the wild； (2) providing a source of individuals for use in the management and restoration of rare birds in nature and (3) providing a means of public education, a fourth goal would include scientific research (Cade, 1994).

Breeding the birds in captivity to supply birds for reintroduction emerged as a goal for many endangered species. At least 83 species of falconiform birds had been bred in captivity by 1984 (Cade, 1986), and self－sustaining captive populations now exist for several species. There is every reason to expect that a self－sustaining captive population can be achieved for this species, and prospects for successful reintroduction also look good. Populations of the Peregrine Falcon have been re－established or significantly increased by fostering, cross－fostering and hacking captive－produced or captive－reared young in Germay (c. 30 pairs reintroduced to vacated range, Hussong 1993), southwestern Sweden and adfacent Norway (c. 16－17 pairs reintroduced), eastern and midwestern North American (c. 150 pairs returned to an unoccupied range) and the Greater Yellow Ecosystem (53 pairs in formerly vacant range). The Mauritius Kestrel increased from what was believed to be two surviving pairs in nature to more than 60 pairs by captive breeding, harvesting wild eggs, fostering and hacking (Cade ＆ Jones, 1993). The Bald Eagle has been reintroduced into New York State by hacking wild eaglets mostly from Alaska (Nye, 1988).

Regard to the proposal of the project for the Crested Ibis, we planed to hopefully release some of young birds that would be reared by the parental birds, but it didn’t achieved the goal due to small population size of captive birds at the present.

However, the Crested Ibis population has increased sufficiently both in the wild and in captivity. A total of 98 birds were produced in Yangxian Ibis Breeding Center during 6 years (1995－2000). In the wild, about 100 birds were proliferated during around 20 years (Lu, 1999； Shi, 1991； Zhai, 1999). It was likely it wold expand into the suitable habitat by reintroduction in the future.

5. Acknowledgements

This project was financially supported by PRO NATURA Foundation that would be greatly appreciated. The authors wish to thank the staff of Yangxian Crested Ibis Breeding Center in China for their kind help throughout the present experiments.

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