Two species of cuckoos are common in the United States east of the Great Plains, the yellow-billed cuckoo[60] (fig. 23) and the black-billed cuckoo,[61] and in the West a relative of the yellow-bill, the California cuckoo,[62] ranges from Colorado and Texas to the Pacific coast. While the two species are quite distinct, the food habits of the yellow-bill and the black-bill do not greatly differ and their economic status is practically the same.

Examination of 155 stomachs has shown that these species are much given to eating caterpillars, and, unlike most birds, do not reject those covered with hair. In fact, cuckoos eat so many hairy caterpillars that the hairs pierce the inner lining of the stomach and remain there, so that when the stomach is opened it appears to be lined with a thin coating of fur.

An examination of the stomachs of 46 black-billed cuckoos, taken during the summer months, showed the remains of 906 caterpillars, 44 beetles, 96 grasshoppers, 100 sawflies, 30 stinkbugs, and 15 spiders. In all probability more individuals than these were represented, but their remains were too badly broken for recognition. Most of the caterpillars were hairy, and many of them belong to a genus that lives in colonies and feeds on the leaves of trees, including the apple tree. One stomach was filled with larvÆ of a caterpillar belonging to the same genus as the tent caterpillar, and possibly to that species. Other larvÆ were those of large moths, for which the bird seems to have a special fondness. The beetles were for the most part click beetles and weevils, including a few May beetles. The sawflies were contained in two stomachs, one of which held no less than 60 in the larval stage.

Of the yellow-billed cuckoo, 109 stomachs (collected from May to October) were examined. They contained 1,865 caterpillars, 93 beetles, 242 grasshoppers, 37 sawflies, 69 bugs, 6 flies, and 86 spiders. As in the case of the black-billed cuckoo, most of the caterpillars belonged to hairy species and many of them were of large size. One stomach contained 250 American tent caterpillars; another 217 fall webworms. The beetles were distributed among several families, all more or less harmful to agriculture. In the same stomach which contained the tent caterpillars were 2 Colorado potato beetles; in another were 3 goldsmith beetles, and remains of several other large beetles. Besides the ordinary grasshoppers were several katydids and tree crickets. The sawflies were in the larval stage, in which they resemble caterpillars so closely that they are commonly called false caterpillars by entomologists. The bugs consisted of stinkbugs and cicadas, or dog-day harvest flies, with the single exception of one wheel bug, which was the only useful insect eaten.

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1915