RIP

 "I'd like to buy one of your zebra finches please."

 - Okay, no problem. Any particular colour?

 "I'd like a white hen."

The customer leaves with the white, female zebra finch that he chose.

Two days later, the customer returns carrying a small cardboard box with him; an obvious sign that there is a problem.

 "I bought a zebra finch from you a couple of days ago."

 - Yes, I remember. Is there a problem?

 "Yes. It was dead this morning. Look!"

He hands over the box. I look inside and, sure enough, there is a dead zebra finch inside.

 "You see? Can I have a refund please?"

 - I can't I'm afraid.

 "Why not?"

 - This is a grey male. You bought a white female.

 "..."

 - ...

 "Oh yeah."