question: If some of the birds are darker than the others.
#1 return birds 
#2 return #1 that are darker 
#3 return number of  #1 
#4 return number of  #2 
#5 return difference of #3 and #4 
#6 return if  #4 is at least one 
#7 return if  #5 is at least one 
#8 return if  both  #6 and #7 are true