Is the cuckoo a good bird or a bad bird?

Pigeons in China's idiom "Nine birds occupy a magpie's nest" refer to cuckoos. Someone on the Internet selected the animal world 10 cheaters and tied for a ranking, with Du Fu topping the list. It is said to be a fierce, cruel and bossy bird, and a rogue among birds. Very irresponsible for raising offspring, too lazy to cook, lay eggs in other nests and be hatched by other birds to feed; Little cuckoo is also very ferocious, not only greedy, but also squeezing all the little brothers and sisters born by adoptive parents into the same nest and crashing to death, enjoying the favor of adoptive parents alone. Du Fu's reputation is really not very good.

But in fact, cuckoo feeds on caterpillars and is a beneficial bird.