食虫性

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.