If the bird on the left faces right and the bird on the right faces left
return bird  ;return #1 on the  left  ;return #1 on the  right  ;return if  #2 faces  right  ;return if  #3 faces  left  ;return if  both  #4 and #5 are true
['select', 'filter', 'filter', 'boolean', 'boolean', 'boolean']