If none of the birds are standing on wood or snow.
return birds ;return wood ;return snow ;return #1 that are standing on #2 ;return #1 that are standing on #3 ;return number of  #4 ;return number of  #5 ;return if  #6 is equal to  zero ;return if  #7 is equal to  zero ;return if  both  #8 and #9 are true
['select', 'select', 'select', 'filter', 'filter', 'aggregate', 'aggregate', 'boolean', 'boolean', 'boolean']