乌鸦，鸟类中的“智慧担当”（完形填空）
You may know the fable: a thirsty crow drops stones into a jar to drink. In a 2014 experiment, scientists ____1____ this — crows dropped stones into a water-filled tube to get food. This reveals the amazing ____2____ of corvids (鸦科鸟) like crows and jays.
Corvids are expert at ____3____ food. One bird can hide thousands of seeds and find them months later. In an experiment, scrub jays (灌丛鸦) ate worms first, leaving peanuts, ____4____ they knew what they stored and when. When they knew no food would be available the next day, they stored more, showing they can ____5____ ahead.
Crows can recognize human faces. In an experiment, after a masked person ____6____ them, the crows later attacked only the person in that mask, completely ____7____ all other masks.They also tend to avoid places where they saw a dead companion, connecting such places with ____8____.
Tool use is another ____9____ skill. New Caledonian crows make hooks from sticks; Japanese crows drop nuts for cars to ____10____ open. Young crows play often, which ____11____the foundation for intelligence.
Their smartness is linked to social life. They raise young cooperatively, share food, and ____12____ against predators. Some form lifelong pairs, responding to each other’s ____13____.