Cuckoos are well known for laying their eggs in the nests of other birds, called brood parasitism. If the unsuspecting parents fail to notice the imposter egg, they'll accidentally end up raising an interloper chick. Cuckoos have evolved a clever trick that allows them to reproduce without having to do the energy-intensive and time-consuming work of parenting.

Sibley's Birding Basics, David Allen Sibley 2002

Beautiful blue cuckoo was still. Still, as if she was glued onto the branch, or as she was just a replica hanging from a wall. What differentiates her from a replica are her eyes. Her eyes were still, but filled with love but also with anxiety. Suddenly, a sound of flapping vibrated the silent forest. Distant, a sparrow returned to its nest, where its beloved chickens await to see the world. The sparrow now rests in its nest. 

1 Sparrow, 2 sparrow chicks. 3 eggs. 1 parent, 2 children,  3 eggs.

 Freedom at last! The cuckoo broke free from the branch and flew across the forest. Her body felt light as if she could now go wherever she wanted to. 

The forest absorbed heat from the sun. Day by day, sunlight stabbed through the trees and leaves, and there was the sparrow, returning to her home. There, three little angels await with open mouths. From a distance, the blue cuckoo watches as her heart fills with hope. As the sparrow feeds her 3 daughters and a stranger, the cuckoo leaps out to the sky, filled with accomplishment. 

The nest was now overcrowded. Not with it’s number but with one of their size. From a distance, the cuckoo observes, hiding behind orange and brown leaves. The beautiful sparrow comes back,  and busily starts filling her angel's mouth. The Cuckoo remains hidden, waiting for the moment of reunion. The forest was now absorbing the bird's heat. She must hurry. 

3 Sparrow and a cuckoo flies through the forest, searching for its new home. Then, another bird comes closer to the four. The intruder continuously disrupts the four. The birds pause their flight. Landing on a tree branch. 

“What’s the ending? Does the cuckoo mom reunite with her kid?”

“I don’t know,”

The boy muttered. Orange light from the sun was now on the edge of being able to light the room. The boy’s eye was locked into the several dots on the wooden floor. Refusing to look at her mother's face. The boy had a feeling facing her would make his thoughts transparent. 

“I mean, Is it going to be a happy ending?”

The boy answered,

“For whom?”