The diminutive house wren[12] (fig. 4) frequents barns and gardens, and particularly old orchards in which the trees are partially decayed. He makes his nest in a hollow where perhaps a woodpecker had a domicile the year before, but he is a pugnacious character, and if he happens to fancy one of the boxes put up for bluebirds, he does not hesitate to take it. He is usually not slow to avail himself of boxes, gourds, tin cans, or empty jars placed for his accommodation.

In food habits the house wren is entirely beneficial. He may be said to live upon animal food alone, for an examination of 88 stomachs showed that 98 per cent of the contents was made up of insects or their allies, and only 2 per cent was vegetable food, including bits of grass and similar matter, evidently taken by accident with the insects. Half of this food consisted of grasshoppers and beetles; the remainder of caterpillars, bugs, and spiders. As the wren is a prolific breeder, frequently rearing in a season from 12 to 16 young, a family of these birds must cause considerable reduction in the number of insects in a garden. Wrens are industrious foragers, searching every tree, shrub, and vine for caterpillars, and examining every post and rail of the fence and every cranny in the wall for insects or spiders.

The house wren is only one of a numerous group of small birds of similar habits. There are within the limits of the United States 28 species and subspecies of wrens, occupying more or less completely the whole country from the Atlantic to the Pacific. With the exception of the marsh wrens,[13] they all appear to prefer some cosy nook for a nesting site, and, as it happens, the farm buildings afford just the place desired. This has led several of the wrens to seek out the habitations of man, and he is benefited by their destruction of noxious insects. No species of wren has been accused of harm, and their presence should be encouraged about every farm, ranch, village, or suburban residence.