Rooster 'groan'?

[BubbaBubbles]

So, I have a sweet roo that in the past month or so reached full maturity. With that came along little chicks for him to father. But even before the chicks eggs were ever even laid, my roo would make a slight groaning noise. He opens his mouth and makes a long "mmhhrrr" that's sort of more pitched? There's no unusual behavior paired with this but he sometimes does it when I'm talking to him in the pen. He doesn't fully trust me, I already know. He likes being near me and comes to me when something scares him but casually lifting him like I do the others isn't something he likes. I've already learned every chicken noise and it's meaning except for this high "groan".

 

[Shabby Chic-Hens]

Try tossing a hen into the air. If he does it then, it’s what I am thinking it is. The random rooster call that they sometimes to when they are displeased, or at other things.