Because they like it
When you are moving your head up and down it is called duck
a duck.
it will bob its head up and down and sing Rihanna's hows that chic.
D U C K Answer: Duck down.
Yes, there is duck when you move down to pick something up which is a verb and duck the animal which is a noun. ^-^
Duck
Bob
Yes. If you train them well enough and have enough face time with them, you can teach them to stand on your finger, and if you bob your head up and down, they will copy you!
BOB BOB BOB
In England, Bob means abbreviation of Robert. In Germany, Bob means famous, bright fame. Bob can also mean to move up and down; the flaot bobs on the water
Poor Bob doesn't do much strumming these days but when he was alive he was a down, down up down up up kinda guy. Sorry, I just couldn't help myself.
Hang a duck upside down while gargling.