How Does A Baby Cuckoo Take Over A Nest In Which Some Of The Host Chicks Have Hatched?

A cuckoo egg that hatches last still manages to effectively hijack a host nest. It cannot push the other chicks out but it is very greedy and aggressive and it demands more and more food from its foster parents. The other chicks, the real offspring of the host parents, soon start to get weak and are then even less able to compete for food.

When this happens, the cuckoo chick, which has grown stronger by the day because of all of the extra food that it has eaten, then pushes the host's own chicks out of the nest easily. They fall to the ground to their deaths.

The host parents are so caught up with parenting, they don't seem to notice that their chick becomes the only one left in the nest or that it grows bigger than they are. Within three weeks the intruder has got big enough to fly off but, if it can, it stays a bit longer to demand food incessantly. Eventually, it does fly off, leaving behind two exhausted foster parents.