Sounds like typical comfort movements to me. These are often observed in calm, comfortable birds, especially after bathing.
Are these Yellow-bills wing clipped or free flying?
DT
DNA sexing:
Zoogen (http://zoogendna.com/Sex_Made_Easy__TM_.html) or Avian Biotech (http://www.avianbiotech.com/sexingcenter.htm). I've used both and have been impressed with their accuracy.
DT
Having a pro teach you how to vent sex or DNA testing (about $20.ea) will be your best bets. Visually sexing geese can be iffy.
Either way your geese look very slick, clean, and healthy. Congrats.
DT
Thanks Waterdog, nice photo. You're one of the folks that I was speaking of who reliably breeds Red-breasted.
Here's a shot of some of mine with young.