철새 중간기착지에서 발생하는 조류사고원인 분석에 관한 연구

Abstract

Migratory birds can travel across ecological barriers such as seas, deserts, and any area inadequate for reside using the wings highly adapted to fast and long-distance movement and the regulatory mechanism for this movement, therefore, they occupy extensive areas in different seasons. However, they need successive stopovers to recharge their energy to complete the journey, thus the quality and the capacity of stopover sites are critical factors for the successful migration. Particularly, long-distant migratory species meet more diverse environments, and as a result, they may have more possibilities to face risks. Therefore, an active and systematic management of their stopover habitat is urgently needed. The study was conducted to support an empirical basis to eliminate risk factors and to suggest necessities of habitat for the successful stopover. I collected data on the mortality of migratory birds from January 2007 to December 2011 on Hong-do (Island), Shinan County, Jeollanamdo Province. A total of 15 Orders 36 Families 130 species 1,338 individuals were collected during the 60 months. Birds in the Order Passeriformes including 16 Families took the most part of the collected birds. Most dominant species were the Ancient Murrelet (Synthliboramphus antiquus, 10.5%), the Black-faced Bunting (Emberiza spodocephala, 7.4%), the Yellow-throated Bunting (Emberiza elegans, 6.7%), and the Olive-backed Pipit (Anthus hodgsoni, 5.6%). Especially, nine species which were designated as the protected species were included in the collected birds. The causes of mortality were categorized into eight groups; 'Killed by cats' was the most dominant cause of mortality (29.3%), followed by 'collision with man-made structures (22.3%)', 'oil pollution (15.0%)', 'unknown cause (10.6%)', 'exhaustion (10.6%)', 'predation by natural enemies (4.6%)', 'traffic accident (0.1%)', and 'others (7.2%)'. Among the cause of mortality, human related factors such as attack by introduced cats, collision with man-made structures and vehicle, oil pollution, and other human-related factors took 73.8% of the total, and natural factors took 15.2%. The mortality was higher in spring and autumn migration seasons, and higher mortality in spring than in autumn may be due to the geographical characteristic of the study site and the different migration patterns between the seasons. Morphological, behavioral and migration characteristics seem to affect the causes of mortality, and it is seems to be species specific. The Japanese White-eye (Zosterops japonicus), the Pale Thrush (Turdus pallidus), the Yellow-throated Bunting (Emberiza elegans), the White's Thrush (Zootera aurea) were the frequently collided species to man-made structures, and the flight pattern seem to affect the mortality and the degree of damage. Patterns of mortality were different between the breeding population (sedentary species) and the non-breeding population (migratory species). The mortality of the breeding population started to be increased from May, the initial breeding season of the study site, and the mortality of the non-breeding population was higher in spring and autumn, the migration season. The factor analysis was conducted to clarify the environmental factors to affect the mortality, and the result showed that the area of windows was the only factor to affect the mortality caused by the 'collision with man-made structures'. Mortality by cats was higher in spring than in autumn, both in the breeding populations (sedentary species) and in the non-breeding population (migratory species). The home range estimated by Minimum Convex Polygon (MCP) method was higher in males than in females. However, there was no difference between the sexes when the home range were estimated by Kernel Estimation (KR). The size of home ranges was significantly higher in autumn than in spring. The home ranges of the six study cats were overlapped in the Hong-do 1 gu village although the sizes of each cats were significantly different. 50% core range of the cats were all villages which implies that the cats are supported food garbages or other food resources, therefore they may highly depend on the human-induced food rather than birds. However, the cats still can be a potential risk factors, because the mortality caused by cats is higher and it may be increased if the quality and the quantity of food available is decreased. Ecological characteristics (ecological niche, migration habits, food, behavioral characteristics), and the landscape pattern of the area that accidents happened (location of buildings, number of cats and natural predators, and environmental pollution such as oil spill) affected the aspect of cause of mortality. Therefore, understanding the basic species specific ecology and risk factors in the habitat can support to make mitigation measures to help decrease the mortality so that it will contribute to protect the endangered species and to increase the biodiversity in a long-term view.