In order to clarify the processes of bioconcentration of organochlorine compounds in birds, residue levels of these compounds were examined in eight species of insectivorous birds and a piscivorous bird, the Eastern Great White Egret, Egretta alba modesta, collected from Korea, during the period from November 1978 to January 1979 and from April to August 1981, respectively. 1. Residue levels of the total organochlorine compounds (PCBs+Σ BHC+ΣDDT) detected from the insectivorous birds averaged 0.42 μg/g in the summer visitors, 0.08 μg/g in the residents and 0.045 μg/g in the winter visitors on the wet weight basis of the pectoral muscles. The difference in the residue levels indicates that summer visitors accumulate organochlorine compounds in their winter range, in Southeast Asia; and that Southeast Asia is much more polluted than are Siberia and Mongolia, the breeding areas for the winter visitors, and also Korea, where some species are permanent residents. 2. The average residue level of the total organochlorine compounds was considerably higher in the adult male egrets (37.24μg/g) than in the adult insectivorous birds. The organochlorine compound concentration was highest in the adult males, and next highest in the adult females; and concentration was still less in chicks, eggs and their prey animals; the difference of the concentration between sexes seems to be caused by a loss of the organochlorine compounds through egg production in the adult female. Stable chemical compounds and isomers predominated in the sample of the egrets, but considerable amounts of relatively unstable ones also were accumulated in prey animals, mainly fishes. Accordingly, it is revealed that birds have a high metabolic ability for organochlorine compounds such as BHC compared with fishes. 3. The concentrations of the organochlorine compounds in the chicks the 1st day after hatching were 1.8-7.2 times higher than in the eggs although there may be considerable individual variation, and decreased afterwards and again tended to increase slightly after the 24th-35th day. This accumulation seems to be related to the increase of food amount and variations of the physiological factors such as metabolic activities and consumption of the body lipids during the growth period of chicks.
韓国内で1978年11月から1979年1月に捕逢した食虫性鳥類8種と,1981年4月から8月に採集した食魚性のチュウダイサギEgretta alba modestaに残留する有機塩素化合物の濃度を測定し,その蓄積特性について研究した.1.食虫性鳥類の胸筋から検出された全有機塩素化合物の平均濃度は夏鳥0.42μg/g,留鳥0.08μg/g,冬鳥0.045μg/gの順であった.これは,冬鳥の営巣・繁殖地であるシベリアやモンゴル,及び供試留鳥の産地である韓国に比して,夏鳥の越冬地である東南アジアにおいてDDTとPCBによる汚染がより進んでいることを示唆している.2.チュウダイサギ雄成鳥における全有機塩素化合物の平均濃度は食虫性成鳥のそれよりもかなり高かった.本種とその餌に残留する全有機塩素化合物濃度は雄成鳥>雌成鳥>雛≒卵>餌の順で高く,雌雄問で認められた残留濃度の差異は,雌成鳥の産卵による排出に起因すると考えられた.また,各化合物の組成を見ると,本種では生体内で安定な化合物が多く残留しているのに対し,主に魚からなる本種の餌には不安定なものがかなり蓄積されていた.このことから,鳥類は魚類に比べ不安定な有機塩素化合物を活発に代謝分解していることが明らかになった.3.各有機塩素化合物の濃度は,卵に比して孵化後1日目の雛で1.8~7.2倍も高かったが,その後に急減し,24~35日目以降ではやや増加する傾向を示した.この成長に伴う有機塩素化合物濃度の変動には,雛及び幼鳥における摂餌量の増加,及び代謝能力や体内脂肪の消耗など生理的な変化が関与していると推察された.