Brood Parasitism

"The best-known example is the European Common Cuckoo. The shells of the eggs of brood-parasites is usually thick. They have two distinct layers with an outer chalky layer that is believed to provide resistance to cracking when the eggs are dropped in the host nest. The cuckoo egg hatches earlier than the host's, and the cuckoo chick grows faster; in most cases the chick evicts the eggs or young of the host species."

caught this on nat geo during dinner time.such a sad fate.the cuckoo looks so huge and ugly as compared to its surrogate parents.Oh well,natural selection at work:(