gander standing on backs of geese

Why are my geese standing on each other backs? I have 10 geese, 3 toulouse females and 1 gander, 3 Embden geese and 3 ganders (I think, I was given 3 extra geese by accident so I'm guestimating based on behavior). I think we have two Embden pairs, a Toulouse pair, and a crossed pair which is...