• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.3 no.3
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• pp.165-171
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• 2022

The Chinese crested tern (Thalasseus bersteini) is one of the most globally endangered species, listed as "Critically Endangered (CE)" on the IUCN Red List, with only approximately 30-49 individuals surviving in the wild. Chinese crested terns were discovered to breed in South Korea for the first time in 2016 while conducting a census on uninhabited islands. The Ministry of Environment has declared the breeding habitat of the Chinese crested terns as "Specified Island" to protect this CE species. However, brown rats (Rattus norvegicus) inhabiting the breeding grounds of the Chinese crested terns and Black-tailed gulls may potentially pose a threat to the breeding of these avian species. Therefore, we conducted a study on the feeding behavior of brown rats involving stable isotope analysis to determine their food sources. Fecal analysis showed that brown rats mainly fed on plants, whereas they scarcely fed on animals, such as insects. In addition, the stable isotope analysis showed that the δ¹³C values of brown rats, insects, and Indian goosegrasses were approximately -16 to -11‰, whereas the δ¹³C value of Chinese crested terns that obtained their food from the marine ecosystem was approximately -22 to -18‰. Hence, we conclude that the source of carbon for brown rats on this island is the terrestrial ecosystem. We ruled out the possibility of any direct prey-predator interaction between the brown rat and the Chinese crested tern or Black-tailed gull.

• Korean Journal of Environment and Ecology
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• v.36 no.2
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• pp.202-216
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• 2022

Animals exhibit certain behaviors and movement patterns as they react to their internal needs, external stimuli, and surrounding environments. They have a bounded range in which they mostly spend their time, and it is referred to as a home range. Based on the fact that the home range is a critical area for the survival and preservation of species, there has been a growing body of research on developing more precise home range estimation methods to use the estimated ranges as a ground for establishing an effective conservation policy since the early 1940s. Recent rapid advancements in telemetry technology that resulted in the presence of autocorrelation between locations with short time intervals revealed the limitations of the existing estimators. Many novel estimators have been developed to compensate for it by incorporating autocorrelation in calculating home ranges. However, studies on the animal home range are still in their early stage in Korea, and newly developed methodologies have not yet been adopted. Therefore, this study aims to introduce the foreign home range estimation methods and foster domestic research activities on home ranges. Firstly, we compared and contemplated seven estimators by categorizing them into geometrical and statistical methodologies and then divided them into estimators that assume independent observations and those that consider autocorrelation in each category. After that, the home ranges of black-tailed gulls (Larus crassirostris) were calculated using GPS tracking data for the month of June and derived home range estimators by applying the methodology introduced in this study. We analyzed and compared the results to discuss the strengths and weaknesses of each method. Lastly, we proposed a guideline that can help researchers choose an appropriate estimator for home range calculation based on the animal location data characteristics and analysis purpose.

• Journal of Wetlands Research
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• v.6 no.1
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• pp.73-87
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• 2004

This study was carried out on Sihwa reclaimed area from January to December in 2003. We observed total 169,351 individuals of 70 species(22 species of waders, 9 species of egrets and 5 species of gulls). Waterbird population was the largest in March(95,465 individuals) and was the smallest from April to June(less than 7,000 individuals). The most dominant species was Pintail(Anas acuta: 58,627 individuals, 34.6%) and other species were Mallards(Anas platyrhynchos: 24.5%), Common Pochards(Aythya ferina: 13.8%), Black-tailed Gulls(Larus crassirostris: 6.1%), Spotbill Ducks(Anas poecilorhyncha: 5.0%) and Greater Scaups(Aythya marila: 2.69%). Sihwa reclaimed area supported many kinds of protected species such as Chinese egrets(Egretta eulophotes), Black-faced Spoonbills(Platalea minor), Eurasian Spoonbills(Platalea leucorodia), Mute Swans(Cygnus olor), Whooper Swans(Cygnus cygnus), and Eurasian Oystercatchers(Haematopus ostralegus). They foraged at waterside of Sihwa lake and rested at reclaimed area. Particularly, Eurasian Oystercatchers bred in habitats with Salicornia herbacea and Suaeda japonica. Reclamation of mud flats and construction of roads, transmission towers and tide embankments disturbed waterbirds in breeding and foraging. We suggest that waterbirds are protected in different action plans according to their status such as breeding, passaging and wintering birds. Maintaining of waterside and swamps in Sihwa reclaimed area will be useful for breeding waterbirds. It is needed to make a protect zone for ecological connecting belt from Oeji isarea, Hyeong isarea, Eum isarea to upper channel on Sihwa lake.

• Korean Journal of Environment and Ecology
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• v.28 no.2
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• pp.113-122
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• 2014

This study was conducted to clarify the community characteristics of wintering waterbirds in Geum River from September, 2011 to March, 2012 (1st) and from September, 2012 to March, 2013 (2nd). 63 species of waterbirds including raptors were observed during the survey. 50 species of 188,673 individuals recorded during the first survey, and 56 species of 116,611 individuals were recorded during the second survey. The dominant species was high dominance dabbling ducks by Baikal Teals, Mallards, Spot-billed Ducks, Greater White-fronted Geese, Black-tailed Gulls and Common Shelducks. We classified the wintering waterbirds into 9 taxa based on the similar ecological characteristics and analyzed the correlation with temperature. As a result, dabbling ducks, diving ducks and raptors showed positive correlation and herons and waders showed negative correlation. Geese, swans and dabbling ducks were high habitat utilization ratio at the Geumgang estuary barrage upstream area, and diving ducks, herons, waders and gulls were high habitat utilization ratio at the Geumgang estuary barrage downstream area.

• Journal of Ecology and Environment
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• v.32 no.4
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• pp.295-304
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• 2009

To understand the properties of soil in Dokdo, we collected soil samples from 12 locations on Seodo and 23 locations on Dongdo, in Dokdo of Gyeongsangbuk-do Province in 2007-2008 and analyzed the soil's physical and chemical characteristics. Sand comprises the largest component (49.37%) of Dokdo soil, followed by silt (40.70%) and clay (9.93%). The soil structure consists mostly of sand loam, followed by loam and silt loam. The pH level of soils from Dokdo varied dramatically among sampling sites and seasons, ranging from 3.36 to 8.02. The total ion content of Dokdo soil also varies greatly among survey places and periods, but in general the total ion content was high in summer when vegetation develops, and low in spring. The exchangeable cation contents of the soil showed low levels in samples where the soil pH was low, including habitats dominated by Agropyron tsukushiense var. transiens and Echinochloa crus-galli, whereas the exchangeable cation contents were high where the organic contents were high, as in habitats dominated by Liriope platyphylla and Artemisia japonica subsp. littoricola. Soil N contents varied greatly among survey sites and higher N contents were found in soil inhabited by Chenopodiaceous plants than in habitats inhabited by other plants. The substantial differences in phosphorus contents among sites were related to excrement of black-tailed gulls. To understand the basic physical and chemical features of the soil on Dokdo, it will be necessary to conduct seasonal and long-term research on soil pH, ion contents, organic contents, N and P, as well as obtaining precise data from samples collected at different depths.

• Korean Journal of Environment and Ecology
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• v.25 no.2
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• pp.123-131
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• 2011

Seabird distribution in the East Sea was studied from April to May 2007 using line transect counts. We observed a total of 1,379 individuals of 23 species including 14 species of seabird. The overall seabird sighting rate was 2.5 birds $km^{-2}$. The Streaked shearwater(Calonectris leucomelas)(74.5%) was the numerically dominant species. Ancient murrelets(Synthliboramphus antiquus)(8.3%), red-throated divers(Gavia stellata)(5.0%), common terns(Sterna hirundo)(2.1%), Pacific divers(Gavia pacifica)(2.0%), and black-tailed gulls (Larus crassirostris)(1.1%) were also frequently observed. The sightings of seabirds was highest between $36^{\circ}N$ and $37^{\circ}N$ of the coastal area of the Korean peninsular. However, the index of species diversity(H') was higher between $35^{\circ}N$ and $36^{\circ}N$. The sighting rates of most observed species decreased with distance from the coastline. The distribution patterns of Streaked shearwater were linked to the variation in the distribution pattern of minke whales(Balaenoptera acutorostrata). Also, spatial segregation was found in the distributions of the two species of divers(Gavia spp.).

• Economic and Environmental Geology
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• v.55 no.1
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• pp.45-51
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• 2022

Whether Dokdo can sustain human habitation or economic life of their own plays an important role to the legal status of the island in the international maritime law. This study reports the hydrological survey results regarding the water resource of the island occurred at Moolgol in Seodo. The amount of underground discharge at Moolgol was estimated at least 1.1 m³/d, conforming the results of previous studies. Based on the oxygen and hydrogen isotope ratios of water, the discharge appeared to originate from precipitation, and about 36% of the daily precipitation moves fast to the Moolgol through the joints developed in the volcanic bedrocks. Quality of the discharged water shows relatively higher concentrations in Cl and NO₃ to be used for drinking and domestic purposes, probably affected by the sea spray and waves from surrounding sea and the birds' excretion such as black-tailed gulls.