Mine go to town on styrofoam.Or if they are dead.
Or if a neighbor super glued their beak shut.
Or if the weird uncle took one for a "date".
I can think of a million scenarios where they might not.
The OP never mentioned free range. Just grape leaves with no mention as to how they happened to get to the leaves.
But the average chicken will eat a quarter pound of feed a day, pellets, grain, greens, bugs, maybe more styrofoam.....
 
	 
 
		 
			
		
		
		
	
	
			
		 
			
		
		
		
	
	
			
		 
 
		
 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		 
 
		