Effects of heavy metal pollution on birds
重金属污染对鸟类的影响

Many widespread and common bird species are at, or near, the top of the food chain and consequently prone to accumulating environmental pollutants. Because levels of heavy metals in the feathers and eggshells of birds reflect the background abundance of these pollutants birds can be useful indicators of heavy metal pollution in the environment. This paper introduces sources and characteristics of heavy metal pollution and describes the threats these substances pose to the environment, with particularly emphasis on the effects of specific heavy metals (Hg, Pb, Cd, As, Cu) on birds. Comparison of concentrations of heavy metals at different levels in the food chain indicates that processes of bioaccumulation and biomagnification cause these pollutants to reach significantly greater concentrations at higher tropic levels, which is where they pose the greatest threat to birds and the environment in general. Previous studies on birds as bioindicators of environmental pollution, the characteristics of heavy metal accumulation in the tissues of birds, directions for future research and guidelines for environmental monitoring are discussed. Herons (Ardeidae), sparrows (Passerinae) and common magpies (Corvidae) are suggested as useful bioindicators of environmental pollution.