흰물떼새(Charadrius alexandrinus)의 번식 성공에 대한 환경 요인의 영향 = Effect of environmental factors on the breeding success of the Kentish plover (Charadrius alexandrinus)

다국어 초록 (Multilingual Abstract)

The nest fate of plovers have been affected from around environmental factors such as vegetation, sediment grain size and others, because these factors correlate with the camouflage and consistent temperature of nest. The Kentish plover (Charadrius alexandrinus) is known to select nest site where vegetation cover is low to easily detect predators. However, recent studies show that their nest successes positively correlate with vegetation cover rate, because vegetation can hide incubating parents from predators. Therefore, in this study, we investigated the relationships between vegetation cover and nest fate, and between breeding success and other environmental factors (such as, sand, shell etc.).
This study was carried out from early March to late July in 2020 at Saemangeum, specifically (1) Mangyeong estuary, Gunsan, Jellabuk-do; (2) Dongjin estuary, Buan, Jellabuk-do. The study area is reclaimed land with sandy coastal environment, and the size of Mangyeong estuary was about 1,011 ha, Dongjin estuary was about 893 ha. Sedges (family Cyperaceae) were the major vegetation in these locations.
We analyzed the effect of environmental factors on the breeding success of Kentish plovers. First, we measured five variables in field: nest diameter (cm), nest height (cm), nest slope (°), distance from nest to the nearest vegetation (m), and the height of the nearest vegetation (cm). Then, we obtained the coordinate of each nest with a GPS and measured distance from nest to water resource (m) using satellite map (Kakao map). We also estimated the cover of environmental factors using 1m² quadrat. The quadrat photos were taken by two ways for each nest: 1) centered on the nest within a 1m²; 2) randomly selected two points in 10m distance from a nest.
On the analysis of variables in quadrat photo, we measured the 11 variables. First, we measured the cover of nest area (mm²) and the cover of five environmental factors (dry vegetation, vegetation, sand (grain size < 2 mm), shell and other object; mm²) on the quadrat photos of centered on the nest within a 1m². Second, we also measured the cover of five environmental factors in each photo and calculated the average of two photos on the each factor on the quadrat photos of randomly selected two points in 10m distance from a nest.
For statistical analysis, we translated variables using “X = log10 (x + 1); X = translated value; x = origin value” before modelling and analyzed using Generalized Linear Model (GLM). The model criteria was Akaike Criteria Information (AIC). Then, we used Mann-Whitney U test to compared variables between successful and failed nests in the best model. All statistical analysis had a significant effect at p < 0.05.
We analyzed 285 quadrat photos (95 photos within a 1m² quadrat centered on each nest; 190 photos on the randomly selected points within 10m area from each nest) from 95 nests: 60 nests in Mangyeong (35 successful nests and 25 failed nests); 35 nests in Dongjin (28 successful nests and 7 failed nests). As the results of GLM, the best model was composed not environmental factors, but three nest factors: nest area, nest diameter and nest slope. In this model, nest area and nest diameter were significant (p < 0.05). However, according to Mann-Whitney test, these factors did not differ between successful and failed nests (p > 0.05). Therefore, when researchers studied the effect of nest factors on the breeding success, nest area and nest diameter should be considered together. On the effect of environmental factors, all factors, which included vegetation and dry vegetation cover, did not affect breeding success. Thus, the other environmental factors should be studied to reveal which one affects the breeding success of Kentish plovers.