I showed this to a friend and they asked how HD could affect something without eyes since in Rohan's introduction it explicitly worked on things that saw his manuscript. Over time Rohan unlocked different ways to use Heaven's Door, he could either show something he'd drawn/written, sketch Pink Dark Boy/Heaven's Door's body in the air, or have the manifestation of Heaven's Door touch the target. He must have used the last one on this chicken.

He can make people fly backwards with massive force by writing they'll do so, so probably.