Grousey's "Moaning" Sound

Today Grousey "helped" me pick tomatoes -- or rather, he helped me NOT pick tomatoes. This wild ruffed grouse has been tracking me for the last 3 months. Sometimes he can be a real obstacle. As shown briefly here, he will pace back and forth in front of me to prevent my passage. And oftentimes he will follow me right up the steps to my door and wait on the landing. More commonly he makes a soft clucking sound, but sometimes he makes this moaning sound. (I posted a slightly longer video where he makes both of his sounds at • Grousey's Two Sounds .) I don't know the significance of the moan, but if anyone knows, please add a comment.