• Ocean and Polar Research
• /
• v.29 no.1
• /
• pp.81-86
• /
• 2007

Abandoned fishing nets served Little Tern(Sterna albifrons) chicks as cover on a sandy island on Ganwol Lake, Hongsung-gun, Chungcheongnam-do, Korea. Chicks were incidently caught in $2.5cm{\times}2.5cm$ mesh sized nets and died of dehydration and exhaustion. Three adults died when they were caught by abandoned fishing net during parental care period in $2.5cm{\times}2.5cm$ mesh sized nets. Whereas $0.7cm{\times}0.7cm$ mesh sized nets did not affect the chicks' or adults' survival. Overlapped nets with several layers were more dangerous for chicks than were spread nets with a single layer. Dead chicks and adults were found to have been entangled by wing and neck. In this study, wing and nape(head+bill) of dead chicks were longer than those of live chicks. To improve the survival rate of Little Tern chicks at Ganwol Lake, abandoned fishing nets must be removed before the breeding season.

• Journal of Ecology and Environment
• /
• v.31 no.1
• /
• pp.37-43
• /
• 2008

We analyzed soil characteristics, soil seed banks, and plant communities in a small islet in Ganwol Lake from May 2005 to August 2006 to examine the forces driving plant settlement on sand bars and the effects of plant settlement patterns on nesting sites of little terns (Sterna albifrons). The soil nutrients contents in a site where the feces of wintering birds accumulate (N: 15.4 mg/kg, P: 10.5 mg/kg, LOI: 0.51 %, pH: 6.8) and a site where organic sediments accumulate (N: 20.7 mg/kg, P: 16.4 mg/kg, LOI: 0.40%, pH: 6.6) were much higher those of a control site which was not affected by bird feces and organic sediments (N: 4.1 mg/kg, P: 5.4 mg/kg, LOI: 0.41%, pH: 6.7). However, a seed bank was formed only on the site with accumulated organic sediments. Plant settlement was accelerated by feces from wintering birds and organic sediment accumulation on sand bars in Ganwol Lake. The percentage of area disturbed by human activities increased from 0.2% in May 2005 to 13.9% in August 2006, and the percentage of annual communities increased from 27.5% to 43.3%, but the percentage of open area decreased from 55.2% to 28.0% from May 2005 to August 2006. These increases in disturbed area and annual communities decreased the open area for breeding of little terns. The enlargement of P. communis and T. angustata communities was suppressed by irregular flooding. These results provide useful information for the management of little tern breeding sites for conservation purposes.

• Journal of Life Science
• /
• v.19 no.11
• /
• pp.1611-1616
• /
• 2009

This study was conducted to determine the characteristics in breeding of the little tern Sterna albifrons in Shinja-do and Doyo-Deung in Nakdong estuary. The data was obtained in the middle and late 1990's and in the mid 2000's, which were analysed for the breeding information of the little tern. In Shinja-Do, a total of 638 nests were observed in 1995, and the average numbers of eggs laid per nest were 2.48. In 2004 and 2005, 94 and 456 nests were observed, and the average number of eggs laid per nest was 2.16 and 2.53, respectively. There was a significant difference between the average numbers of eggs laid per nest for the 3 respective years. In Doyo-Deung, a total of 269 nests were observed in 1998, and the average number of eggs laid per nest was 2.16. In 2004 and 2005, 1,023 and 1,123 nests were observed, and the average numbers of eggs laid per nest were 2.33 and 2.52, respectively. There was a significant difference (p<0.001) between the average number of eggs laid per nest as well. Hatching success rate by nesting site in Shinja-Do was calculated in 1995. Type A nest (nest located on dry sand land) showed a 56.8% success rate, and type B nest (nest located on the land with dwarf grass), type C nest (nest located on moist land) and type D nest (nest located on the land with shells) showed 55.3%, 36.6% and 59.3% success rates, respectively. The average hatching success rate in Shinja-Do was 54.5%. The most crucial factor for hatching failure was flood, especially, for the type C nests. The hatching success rate by the nesting site in Doyo-Deung showed an average of 73.2%. It was high in type D nest (83.8%) and type A nest (75.9%), and low in type C nest (59.7%). Again, the most crucial factor for hatching failure was flood, especially, for the type C nests. Nakdong estuary has been through many changes over time, particularly in recent. Therefore, continuous efforts to keep it a breeding place for the little tern are urgently required, including overall management of land, protection of reef and sand, etc.

• Journal of Ecology and Environment
• /
• v.29 no.6
• /
• pp.545-550
• /
• 2006

Ten supernormal clutches of little terns Sterna albifrons and seven clutches having mixed eggs by little terns and kentish plovers Charadrius alexandrinus were recorded during the breeding seasons of 2003$\sim$2005 at Ganwol lake, Hongsung-gun, Chungcheongnam-do, Korea. The frequency of egg retrieval by Little Terns was higher after the second egg laying regardless of the clutch size and incubation stage. The frequency of egg retrieval was high at all incubation stage. When experimental eggs were placed within 15 cm from the nests, the percentage of egg retrieval was highest (almost 100%). However the percentage dropped rapidly over 35$\sim$55 cm range and finally to zero at 60 cm distance. Little terns retrieved all kinds of eggs set near their nests regardless of its kind or size. This study suggests that egg retrieval by little terns may be a source of the nest with supernormal and mixed egg clutch observed in this species.