“Yes,” assented Jules, “but it is so tiny a creature it can’t do much work.”
“If the wren hunted big game, certainly at the end of the day it would not have captured its prey by the dozen. What could such a little thing do with a June-bug? It would not come to the end of such a supply of food for several days.”
“And the June-bug would be too hard for its beak, too,” remarked Jules.
Long-billed Marsh Wren
“What it needs is the smallest of caterpillars and the tiniest of gnats, which make a more delicate mouthful and are better adapted to the bird’s small throat. I need not remind you that the worst foes to our crops are the smallest. A grub too tiny to catch the eye endangers our cereals, and others equally small ravage our fruit while it is still in the bud. How much does it take to destroy a blossom that would produce a pear the size of your two fists? One single larva just visible [[217]]to the naked eye. Well, the wren attacks these tiny foes of ours that are all the more troublesome because we cannot see them easily. Now guess how many little caterpillars a day the wren needs for feeding its brood. Observers whose patience I admire have calculated the number.”
“Let us say ten caterpillars to each little bird,” replied Jules, “and ten little birds in the nest. That would make a hundred caterpillars a day, and it is certainly a lot.”
“A lot! Ah, how far out you are in your reckoning! The mother wren brings something to her little ones at least thirty-six times an hour. She feeds them a mixed diet of insects, larvæ and eggs. At the end of a day the number of insects destroyed, of one kind and another, amounts to one hundred and fifty-six thousand. That leaves your paltry hundred a long way behind, my dear Jules.”
“Then the caterpillars must be very small, or the brood of wrens would die of indigestion.”
“Undoubtedly they are exceedingly small, and then a great many are not even hatched yet; but the result as far as we are concerned is just as important, so many eggs devoured meaning so many ravagers the fewer a little later.”