Cuckoo - The Enemy In My Nest

Cuckoos are brood parasites - they lay their eggs in the nests of other bird species. While it is a clever strategy by cuckoos, why do other birds allow this to happen? While cuckoo eggs resemble other eggs, the cuckoo chick is giant in size! How do other birds don't notice this? Or do they benefit by rearing cuckoo's chicks? Experts try to solve this evolutionary riddle.