Although the eggs of the various host species include a number of different colours and patterns, there is always a similarity in appearance between the cuckoo's eggs and of the host.

A female cuckoo normally deposits only one of its eggs in each host nest and takes away of the host's, sure that the same number will remain there were in the first . If birds notice a strange egg in the they either build another nest on of the first, or else with the problem by getting of the strange egg.

But cuckoos rarely make the of leaving their eggs in a nest that to the wrong host, where they would be recognized. We do not know the cuckoo learns to distinguish suitable nests but it seems to be the result of a process that place while the female cuckoo is being up by foster parents.

The remarkable feature of the process is that so cuckoo eggs are lost, only 8% of the total.