Circles of Ice

I was just about to leave the local millpond, when I noticed these circles. 4 questions entered my mind. How, why, when, and what...with the emphasis on the how. Some of them are almost perfect circles. How...how...how?

I was about to give up knowing when the duck couple entered the scene. The male jumped out of the water, and dragged his webbed foot round and round on the ice. He then breathed hot and heavy on the circled line he had created, and finally the piece broke off. I thought the show was over.

But the duck grabbed the big circle, and threw it up into the air...like a big hunk of pizza dough...spinning the ice circle, and having it land on his beak. Then, the talk.

HIM: "Quack, quack, quack." ("Do you want peppers and onions on that?")
HER: "Quack, quack." ("Yes, but easy on the peppers. They don't treat me well...if you know what I mean.")

Obviously, that's not how it happened, so I'm counting on someone (YOU?) to offer me an explanation. In the right hand lower corner, you can see a circle being formed...before it enters the drink.

Answers...answers...answers! I NEED ANSWERS!!