05:37 Sep 15, 2011 

The cuckoo removes and eats one egg from a number of nests built by other species, replacing it with an egg of her own. She then migrates, leaving an unsuspecting foster parent to hatch and rear her offspring. Shortly after hatching, the nestling cuckoo - which hatches earlier than the young of other birds - destroys all the other eggs in the nest by tipping them out. It then rapidly outgrows the entire nest, fed energetically by foster parents that may actually be four or five times smaller than it.
...Under these circumstances it is difficult to see why the cuckoo is also synonymous with idiotic behaviour, but easy to understand the origins of cuckold.