If you don't want to watch the whole thing, skip to 1:08, 1:35 and 2:50. These are our two silver Appleyard drakes, Piglet (all white) and Angus getting their "grunt and whistle" on!
Angus (our big silver Appleyard drake) does this year round! It's funny...he postures and postures until all the girls are looking at him before he does it. :-)