"Bird Dog" joke

Bob was showing off his bird dog to his friend Bill. They went down towards a lake and Bob said to the dog, "How many ducks are there boy?"
The dog raced off to the lake, came back a couple of minutes later, and barked twice. Seconds later, two ducks floated into view.
"That was unbelievable, can he do it again?" Bill asked.
"Sure," responded Bob, "How many ducks are there boy?"
The dog raced off again, came back, and barked four times. Four ducks flew in and landed on the pond.
"I have to have that dog," Bill said, "I'll give you $5,000 and all of my hunting dogs."
They agreed to the deal, and Bill took the dog home to show off to his wife.
Bill and his wife took his new dog down to the lake and Bill said, "How many ducks are there boy?"
The dog raced off, came back, grabbed a stick, shook it, and threw it over his shoulder.
"Bob gypped the hell out of you," his wife said, "that dog just wants to play fetch."
Bill protested, "But I saw it work, let me try again. How many ducks are there boy?"
Again the dog raced off, came back, grabbed a stick, shook it, and threw it over his shoulder.
"You are such a fool," said the wife.
"This dog is useless," Bill said. In a fit of rage he shot the dog. Later he complained to Bob.
Upon hearing the story, Bob cried, "You idiot! He was telling you there were more ducks than you could shake a stick at!"