Scottish Fairy and Folk Tales, by George Douglas, [1901], at sacred-texts.com
A FOX had noticed for some days a family of wrens, off which he wished to dine. He might have been satisfied with one, but he was determined to have the whole lot--father and eighteen sons,--and all so like that he could not tell one from the other, or the father from the children.
"It is no use to kill one son," he said to himself, because the old cock will take warning and fly away with the seventeen. I wish I knew which is the old gentleman."
He set his wits to work to find out, and one day, seeing them all threshing in a barn, he sat down to watch them; still he could not be sure.
"Now I have it," he said; "well done the old man's stroke! He hits true," he cried.
"Oh!" replied the one he suspected of being the head of the family; "if you had seen my grandfather's strokes you might have said that."
The sly fox pounced on the cock, ate him up in a trice, and then soon caught and disposed of the eighteen sons, all flying in terror about the barn.