Now and than a magpie would call.

不时有喜鹊的叫声。

Herons (Ardeidae), sparrows (Passerinae) and common magpies (Corvidae) are suggested as useful bioindicators of environmental pollution.

建议选择野生鹭类、麻雀和喜鹊等类作为指示生物监测环境中的重金属污染。