Chick Colour Change

One day one hen went out with her six chicks.
hen went kept on going by observing her chicks carefully.
The chicks followed the hen by eating the seeds and ants in the mid-way.
They went so long.
The chicks following the hen saw a smoke tunnel on the roadside.
They got into the tunnel and came from the other side.
By then the hen looked back and got tensed by not having chicks behind her.
As the hen got worried and not getting what to do she shouted “kokorokko”.
As the chicks came out from the smoke tunnel the chicks turned into the black colour.
The hen didn’t recognize them.
As the chicks heard the hen voice, they too shouted “kokorokko” slowly.
The hen didn’t recognize the colour changed chicks. But she recognized their voice.