• Ocean and Polar Research
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• v.41 no.2
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• pp.99-105
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• 2019

Black-tailed gulls, Larus crassirostris, have been known as resident birds in Korea, but their wintering and breeding habitat ranges were little known about. We investigated the habitat ranges of Blacktailed gulls breeding on Dokdo Island - which is the eastern end of their breeding colonies in Korea. Three adult Black-tailed gulls were fitted with Global Positioning System data loggers in May 2018 and their positions were tracked for 9 days, 245 days and 365 days each respectively. Black-tailed gulls stayed on Dokdo Island until June for breeding purposes and moved down to the southern part of Japan for wintering. The following year, a Black-tailed gull started to move northward in February and returned to Dokdo Island in April. They traveled a total of $207,334-229,507km^2$ (MCP) throughout a whole year. Based on location density categories accounting for 50% of locations, they used 3,618 to $3,803km^2$ in area. Black-tailed gulls breeding on Dokdo Island used smaller habitat ranges during the wintering period than the other periods. This is the first report on the habitat ranges of Black-tailed gulls breeding on Dokdo Island.

• Korean Journal of Environmental Biology
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• v.35 no.2
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• pp.134-142
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• 2017

Nando Island is reported as one of the biggest breeding colonies of seabirds in South Korea, and is protected as a Natural Monument. This study was conducted between July to November 2015, to investigate the breeding population of Black-tailed gulls and their habitat on Nando Island. We estimated the breeding population of Black-tailed gulls (Larus crassirostris) using nest density. The mean nest density of Black-tailed gulls was $0.51\;per\;1m^2$ ($0.51m^{-2}$), and the breeding population was approximately 26,760 individuals. The dominant vegetation was Echinochloa crusgalli and Agropyron tsukushiense var. transiens, which served as shelter and nest sites to Black-tailed gulls. The diet of Black-tailed gulls was mainly the fish, Japanese Anchovy Engraulis japonicas (48%). Other species which were found to breed on Nando Island were Streaked Sheawater (Calonectris leucomelas), Temminck's Cormorant (Phalacrocorax capillatus), and Swinhoe's storm petrels(Oceanodroma monorhis).

• Animal cells and systems
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• v.6 no.3
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• pp.221-225
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• 2002

This study was conducted to find out how young black-tailed gulls (Larus crassirostris) recognize adult voice signals after hatching. For the experiment, adult voice recorded in the natural environment was played back at controlled intervals and intensity (dB) to 15 young gulls that were artificially hatched in the laboratory. The chirirah call frequency of young gulls increased as the intensity of the mew call increased. The chirirah response of the control group was highest to the mew call at intervals of 1.8s. The adult long ca11 and alarm call also showed similar results to the mew call when the interval and intensity were manipulated similar to the mew call. Based on the results of this experiment, it is assumed that the young black-tailed gulls recognize adult voice signals based on the simple structure of adult voice signals, that is, the interval and intensity of the voice.

• The Korean Journal of Ecology
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• v.25 no.6
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• pp.365-369
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• 2002

We had 18 eggs artificially hatched in a mass breeding place of black-tailed gulls and examined the individual recognition between young siblings in a laboratory environment. The results of the experiment showed that the young gulls selectively responded to their siblings and non-siblings at an early stage after hatching. It was shown that they began to recognize the begging call among the voice signals of siblings and non-siblings 15-16 days after hatching, and the chirirah call 11-12 days after hatching. Also, more significant results were shown with the chirirah call than with the begging call. In an experiment of visual recognition between siblings and non-siblings, the young black-tailed gulls approached their siblings significantly 9-10 days after hatching. The recognition between young siblings in a mass breeding place provides an important evolutionary indicator in terms of their social behaviors.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.14 no.4
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• pp.87-93
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• 2006

The black-tailed gull chicks, Larus crassirostris, recognize various adult voice signal base on the simple patterns. We investigated behavior change in black-tailed gull chicks through physical manipulation of mew call. They were playback in four situations differing in physical character: 1) frequency manipulation only, 2) duration manipulation only, 3) call intensity(dB) manipulation only, and 4) call interval manipulation only. We observed occurrence of different response of the chicks, which were categorized into two behaviors(hidden and return behavior). The manipulated frequency, duration, and intensity were directly correlated. The chicks exposed to only manipulated call interval(0.5, 1sec) made significantly more hidden and return behavior. Adult black-tailed gull only increased flight time on manipulated call interval. The results suggest that black-tailed gulls use short call interval for alarm signal. The analysis of alarm signal provides an important on basic study of bird strike.

• Journal of Ecology and Environment
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• v.29 no.1
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• pp.35-39
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• 2006

During the breeding seasons in 2002 and 2003, the influences of vegetation cover on breeding processes of Black-tailed Gulls (Laurs crassirostris) were studied on Hongdo Island. We checked dutch sizes, calculated hatching success and survival rates on day 15 and a vegetation cover, There was significant positive relationship between vegetation cover and hatching success, and survival on day 15. In order to analyze the relationship, sample nests were categorized as 'exposed' and 'covered' nests, and the breeding processes at each nest were compared. Hatching success and survival on day 15 in covered nests were significantly higher than ones in exposed nests. However, in clutch size, there was no significant difference. The rate of the hatching and survival failure was different amongst the categorized nests. The primary cause of hatching failure in covered and exposed nests was 'disappeared', and the primary causes of survival failure on day 15 were 'disappeared' and 'killed by adults'. The failure in exposed nests was significantly larger than that of covered nests. In the breeding of Black-tailed Gulls on Hongdo Island, vegetation cover influenced the survival of eggs and chicks as the cover provided shelter against predators and extreme weather.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.5 no.2
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• pp.37-42
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• 2024

This study used a GPS tracker to determine characteristics of wintering habitat use by black-tailed gulls on the west coast of Korea. Results of this study showed a southward movement in December and a northward movement in March. The wintering habitat was confirmed to include the southwest coastal island area (Group 1), the inland coastal area (Group 2), and China (Group 3). The wintering home range was the narrowest in October and the widest in December. Home range of Group 1 was increased from November, showing the maximum in December, decreased in February, and then tended to increase again in March. Group 2 showed the widest home range in November and a narrow range of home range from December. Home range of Group 3 showed a mixed pattern of group 1 and group 2. The flight rate was the lowest in January and the highest in March. Day and night flight rates showed significant differences by month. This study identified wintering characteristics of the West Coast population of black-tailed gulls on the West Coast, including their wintering areas, migration periods, and use patterns. These wintering characteristics of black-tailed gull in the west coast area are thought to be affected by environmental factors (such as food resources and fishing activities) and geographical characteristics of the West Coast where many islands are distributed.

• Journal of Ecology and Environment
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• v.30 no.1
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• pp.9-15
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• 2007

Black-tailed gulls (Larus crassirostris) produce alarm calls apparently related to their anti-predator behaviors, but the hypothesis that the calls are actually used as functionally referential alarm signals has not yet been tested. In this study, we performed a series of experiments using visual (a stuffed goshawk: Accipiter gentilis) and acoustic (alarm calls and a control vocalization) stimuli at 15 sites in Sinjindo-ri and Dowhang-ri, Taean-gun, Chungnam province to examine anti-predator responses of the gulls to alarm calls in playback trials. We found that the gulls' visual recognition of a perched hawk model in the absence of alarm vocalizations was weak or absent because the model was noticed in only two out of 16 trials. The gulls' responses to playbacks of the alarm call only and the alarm call with a visual stimulus differed from responses to the control vocalization in latency to approach, time mobbing, and the percentage of gulls responding, while the responses to alarm call only differed from alarm call with a visual stimulus in latency to first fly, latency to call, and time mobbing. The results of this study suggest that alarm calls of black-tailed gulls are used to elicit appropriate anti-predator behaviors that are intensified when a predator is detected visually.

• Journal of Environmental Science International
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• v.27 no.12
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• pp.1279-1290
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• 2018

Sea gulls are high trophic level consumers in the coastal environment, and thus, which have been widely used to monitor contamination biomagnified through a food web. However, such monitoring studies using sea gulls have been rare in the Korean literature. The National Environmental Specimen Bank chose eggs of a black-tailed gulls (Larus crassirostris) to serve as an environmental specimen for the long-term monitoring of the coastal ecosystem affected by terrestrial pollutants. Black-tailed gull eggs were collected from Baengnyeongdo, Hongdo and Uleungdo, and their DDTs and total mercury content were determined. The highest concentration of ${\Sigma}DDTs$ was $231.6{\pm}106.1{\mu}g/kg$ wet in Baengnyeongdo, followed by $230.0{\pm}123.8{\mu}g/kg$ wet in Ulleungdo, and $117.7{\pm}18.3{\mu}g/kg$ wet in Hongdo. In addition, total mercury was detected at $414.5{\pm}97.6{\mu}g/kg$ wet in Ulleungdo, $363.9{\pm}123.6{\mu}g/kg$ wet in Hongdo, and $237.5{\pm}42.3{\mu}g/kg$ wet in Baengnyeongdo. Relatively high concentrations of the target pollutants were recorded in specimens from Ulleungdo. Additional comprehensive and prolonged studies are required to elucidate spatial and temporal patterns of contamination in black-tailed gull eggs with regard to monitoring contaminant trends in eggs and prey.

• Journal of Ecology and Environment
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• v.31 no.1
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• pp.69-73
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• 2008

We studied the functional roles of two types of calls, mew calls and mobbing calls, of the black-tailed gull (Larus crassirostris) by examining responses of mixed flocks of gulls to the playback calls. Playback experiments were conducted on four days between 11 May and 5 June 2007 at 16 sites in Sinjindo-ri and Dowhang-ri, Taean-gun, Chungnam province and Imjado, Sinan-gun, Jeonnam province, South Korea. We examined the anti-predator responses of the gulls to the playback trials. We found that gull flocks initially responded to mew call playbacks by mobbing in less than half of playback trials (6/14) while all trials involving playbacks of the mobbing call and control (group mobbing) call evoked mobbing. When trials in which no response was recorded were excluded, we found that the gulls' responses to mobbing and group mobbing call playbacks was more intense than their response to mew call playbacks, in that gulls mobbed longer, more gulls responded, and gulls took flight after a shorter time interval. However, the intensity of the gulls' response did not differ in mobbing call and group mobbing call playbacks. The results of this study suggest that the mixed-species flocks of gulls discriminate between the mew calls and the mobbing calls.