What is hidden in 3D image?

There once was a Red Indian whose given name was "Onestone". So named because he had only one testicle.
He hated that name and asked everyone not to call him Onestone.
After years and years of torment, Onestone finally cracked and said,
"If anyone calls me Onestone again I will kill them!" The word got
around and nobody called him that any more.
Then one day a young woman named Blue Bird forgot and said, "Good morning, Onestone."
He jumped up, grabbed her and took her deep into the forest where he made love to her all day and all night.
He made love to her all the next day, until Blue Bird died from exhaustion.

The word got around that Onestone meant what he promised he would do.
Years went by and no one dared call him by his given name until a woman named Yellow Bird returned to the village after being away
for many years.
Yellow Bird, who was Blue Bird's cousin, was overjoyed when she saw
Onestone. She hugged him and said, "Good to see you, Onestone."

Onestone grabbed her, took her deep into the forest, then he made
love to her all day, made love to her all night, made love to her all
the next day, made love to her all the next night, but Yellow Bird wouldn't die!

So what is the moral of this
story?????............................
You can't kill two birds with one stone!!