Many people just see crows (乌鸦) as a natural clean-up crew—eating insects, dead animals or food in trash cans. But researchers have found that crows are not only playful but also social and intelligent. They use tools to solve problems, and they remember faces for years and copy sounds they hear.
"Crows are always testing their environment," said John Marzluff, University of Washington professor of wildlife science. "Anything that looks possibly edible, they will taste it." This trait (特点) has led to interesting scientific findings. Some crows use sticks to gain hard-to-get treats. In other experiments, they learned to drop stones into narrow containers to raise water to a level where they can drink it or reach a floating treat inside.
Crows are social, living in large extended families of more than a dozen birds. Communication is key to their survival. Many calls are used—each having a different message. For example, they have separate warning calls for cats, dogs and people. Some crows even imitate the sounds of other animals and people.
Marzluff did several experiments to determine whether wild crows remember human faces. In one, researchers wearing masks caught seven crows around the campus and banded them. After setting them free, researchers found that regular passers-by got no reaction, but as soon as anyone wearing the same mask passed by, the crows made loud warning calls—even years later. Never be mean to a crow. They not only remember faces but teach their offspring who to beware of (当心). They also remember those who were kind to them and pass that information along, too, often bringing gifts of rocks or other small objects as a thank-you.
