멸종위기종 팔색조의 보전생물학적 연구

Abstract

Recently, Jeju Island was recognized as the largest breeding place of Fairy Pitta (Pitta nympha) in Korea, however there are only few studies on the distribution and ecology of this species. The maintenance or increase of endangered species'population are important for species preservation, thus understanding their breeding mechanism, breeding site and genetic structure are necessary. The size of Fairy Pitta population is influenced by habitat environment, natural enemy, artificial things, and genetic diversity. In this study, the changes in the habitat environment were investigated by comparing Landsat satellite images and existing literature from 1970s´ to 2000s´. Also, the causes of injury and mortality of Fairy Pitta were investigated. Finally, the genetic structures of Fairy Pitta's population that inhabited Jeju Island, Korean Peninsula and Taiwan were compared using mitochondria CO1 and Cyt-b genes.

1. Characteristic of population breeding The Fairy Pitta arrived at the breeding site at the end of May and as soon as they arrived, the male wandered for the breeding site and made a sound to find its mate and defend its territory. Egg-laying was observed in early June, with the earliest egg recorded on June 1, 2012, while the last egg-laying was recorded on July 23, 2007. Most of the egg-laying or approximately 68% occurred in the month of June. The most frequent clutch size was 5(46% of the clutches found) and the mean for 97 clutches was 4.5 (±0.83) eggs (range: 3-6). The mean clutch size on the tree (4.0±0.63) was lower as compared on the rock(4.8±0.75). It was observed that the Fairy Pitta incubated for 13 – 14 days and the nestlings were fed for 13 – 14 days. Earthworms were the most common food for nestlings, averaging 82% of all the food items. In this study, it was observed that the breeding success (i.e., eggs laid giving rise to fledged young) of the Fairy Pitta was approximately 41.9%.

2. Characteristic of breeding site The altitude range of the habitats which Fairy Pitta inhabited in 1960s is different from today's habitat in Jeju Island. The habitat environment was investigated in this study to understand the cause of the changes by comparing the satellite image data (Landsat) between 1975 and 2002 and literatures on Fairy Pitta´s habitats, vegetations and forest landscapes. At present, Fairy Pitta mainly inhabited in forest areas with below 600 asl(above sea level), which was massively pastured before that had small isolated forests in the nearby valley. These forests had broad-leaved evergreen forests, and the secondary forests had a poor condition in terms of size and forest structure. The forests with 700m asl were also a secondary forests with trees having approximately 3m height. The forests from 800m to 1300m asl were also disturbed due to the mushroom cultivation conducted by the local people. It was also observed that the Fairy Pitta could not inhabited in the areas with more than 1300m asl due to the poor forest conditions in terms of size and structure which consist of Ilex crenata, Rhododendron mucronulatum var. ciliatum and coppice forests. Therefore, it might be possible that the best forests habitat for the Fairy Pitta in 1960s were located in areas with 1,000m to 1,300m asl. In comparison to present habitats, the sizes of the habitats before were smaller having a lesser population of Fairy Pitta in the forests with 100m to 800m asl. However, due to the successful improvement of the forest landscape in Jeju Island since 1960s, the population of Fairy Pitta increased. In the analysis of the breeding sites, 39 of the total 70 nest were found on rock, while 28 were found on the trees which mostly were evergreen broad-leaved trees (86%), and 3 were found on the incline. Nests were found between 0.8m and 4.6m high, with the 74% of the nests were located at heights between 1 to 3m. Mean distance from the edge of valley to nest support on the rocks was different as compared to the trees. The nests were characterized to have dorm shape, and most of them were oval. To protect the Fairy Pitta and their habitats in Jeju Island, it is suggested that sustainable forest management that focuses on the species composition and stand structure that protects and enhances the biodiversity must be implemented.

3. Causes of injury and mortality The Fairy Pitta (Pitta nympha) is considered as an internationally threatened species, but there is a little quantitative information on threats in breeding areas of this species worldwide as well as in Korea. This study examined the causes of injury and mortality of Fairy Pittas in Jeju Island, Korea from 2002 to 2012. A total of 30 cases which mainly occurred from the month of May to July were observed. The identified causes of injury and mortality were predation (11 cases, 36.7%), and window strike (11 cases, 36.7%), followed by car accidents (three cases, 10.0%), natural disasters (floods; two cases, 6.7%), dehydration (two cases, 6.7%), and human disturbances (one case, 3.3%). The most affected age class was after hatch year (AHY) birds (18 cases, 60.0%) followed by eggs (eight cases, 26.7%), raising a conservational concern that the high injury and mortality rate during AHY may reduce effective population size of Fairy Pittas in Jeju. Particularly, buildings which are located in forests significantly threatened Fairy Pittas. Therefore, mitigation and conservation measures such as window strike prevention, regulations of new building and road construction in key forests, control of corvid predators, and human disturbance reduction should be considered in Jeju Island, which is the most important breeding areas of the Fairy Pitta in Korea. In conclusion, in addition to the known threats to Fairy Pitta populations including habitat loss and lowland deforestation, the results of this study suggest that human-related mortality, including window strikes and traffic accidents as well as predation may adversely and significantly affect the survival of individual Fairy Pitta, raising new conservation concerns in human-dominated environments.

4. Population genetic structure A Fairy Pitta is a bird known to breed only in mainland China, Taiwan, Japan and Korea and is listed as Vulnerable in the IUCN Red List. This study was carried out to analyze the DNA in order to contribute in the conservation of the genetic diversity of Fairy Pitta. A total of 34 samples were collected in Jeju Island, the Korean Peninsula and Taiwan from 2004 to 2013. The DNA was extracted from them and several sequences were amplified through PCR and the population genetic analysis was then performed. Results showed that there was a transversion between nucleotide sequences at CO1 gene, while there was no changes at Cyt-b gene. It was confirmed that the polymorphism from two genes was caused from genetic drift and not from selection. Through this analysis, the group within the Korean Peninsula was found higher than the other two groups based on the analysis of CO1 gene, and the group from Taiwan was found higher than other two groups through the analysis of Cyt-b gene. The population genetic structure of mitochondria gene of three groups showed that the CO1 gene had 5 haplotypes and Cyt-b gene had 6 haplotypes. Haplotype 2 in CO1 gene was found in the three groups and many individuals samples had this haplotype. Like CO1 gene, haplotype 2 in Cyt-b gene was found in three groups and was found in plenty of individuals. It was also observe that the other haplotypes did not overlap among the three groups or other haplotype was not found in other groups. To prevent the Fairy Pitta from extinction and to obtain the genetic diversity, a more comprehensive study is needed that will compare the result of this study with other regional group such as Japan, China and additional research in the non-breeding area must also be conducted.