麻雀Sparrow

我们在城市里见到的「麻雀」几乎都是树麻雀。头顶栗褐色，两侧脸颊各有一块清楚的黑斑，这块「腮红」是它最好认的特征。雌雄外形相似。Almost every “sparrow” we see in Chinese cities is the Eurasian tree sparrow. It has a chestnut-brown crown and a clear black patch on each cheek — this “blush” is its easiest identifying feature. Males and females look alike.

它曾在 1950 年代的除「四害」运动中被列为清除对象，因为被认为大量偷食谷物。数量锐减之后，虫害反而加重——麻雀在育雏期主要捕食昆虫。后来它被从名单中移除，各地也重新补充了种群。这段经历常被当作一个生态学教训：判断一个物种「有害」还是「有益」，不能只看它在某一个季节做了什么。In the 1950s “Four Pests” campaign it was listed for elimination, because it was thought to eat large amounts of grain. After its numbers crashed, insect damage actually got worse — sparrows feed mainly on insects while raising their young. It was later removed from the list, and populations were replenished in many places. The episode is often cited as an ecological lesson: whether a species is “harmful” or “useful” cannot be judged by what it does in a single season.