question: If the bird on the left is facing right and the bird on the right is facing left.
#1 return birds 
#2 return #1 that is on the  left  
#3 return if  #2 is facing right  
#4 return #1 that is on the  right  
#5 return if  #4 is facing left  
#6 return if  both  #3 and #5 are true