Animal food.—Beetles, collectively (20.40 per cent), constitute the largest item of animal food. Of these, 2.23 per cent are the predacious ground beetles (Carabidæ), generally considered useful. The remainder belong to several more or less harmful families, of which the May-beetle family (Scarabæidæ) amount to 10.17 per cent. Snout beetles, or weevils (Rhynchophora), are eaten to the extent of 2.16 per cent only, and the wood-boring chick-beetles (Elateridæ) to 2.13 per cent.
Among the various species of these insects were noted the remains of the well-known Colorado potato beetle (Leptinotarsa decemlineata), in two stomachs, and Coptocycla signifera, also injurious to the potato, in one stomach. Remains of Otiorhynchus ovatus, a weevil destructive to strawberry plants, were found in two stomachs, and in one other a weevil, Sphenophorus parvulus, that injures the roots of grass. The well-known white grubs that attack grass roots and a host of other plants are the immature forms of many species of Lachnosterna, of several species of Euphoria and of Allorhina nitida. Of these, remains of Lachnosterna were found in 27 stomachs and of Allorhina and Euphoria in one each.
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B2084-73 Fig. 1.—Wood thrush (Hylocichla mustelina). |
Lepidoptera (caterpillars) stand next to Coleoptera (beetles) in the animal diet of the wood thrush. Although eaten with a fair degree of regularity during every month of the bird's stay in the north, the most were taken in July (16.32 per cent). The average for the season is 9.42 per cent. Ants as an item of food are third in importance, though if other Hymenoptera were included the order would rank next to beetles. They seem to be a rather favorite food with all birds of the genus Hylocichla. With the wood thrush they begin with 18.12 per cent in April and gradually decrease through the summer and disappear in October. The total for the season is 8.89 per cent. Hymenoptera other than ants were eaten with great regularity (3.86 per cent) throughout the season, but not in large quantities. Diptera (flies) are eaten in small quantities and rather irregularly. Most of them were the long-legged crane flies (Tipulidæ), both in the adult and larval form. The total for the season is 2.70 per cent. Hemiptera (bugs) do not appear to be a favorite food, though a few were taken in all of the seven months except October. The average for the season is only 1.33 per cent. Orthoptera (grasshoppers) are eaten in small quantities until July, after which they form a fair percentage till September. The total consumption amounts to 2.28 per cent of the food. A few other insects make up a fraction of 1 per cent. Spiders and myriapods (thousand-legs) appear to be a favorite food with the wood thrush, constituting in April 20.94 per cent of the food, but gradually decreasing in quantity until September. The aggregate for the year is 8.49 per cent. A few sowbugs (isopods), snails, and earthworms (1.83 per cent) close the account of animal food.
Following is a list of the insects identified in the stomachs of the wood thrush and the number of stomachs in which each was found:
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Vegetable food.—More than nine-tenths of the vegetable food of the wood thrush can be included in a single item—fruit. Cultivated fruit, or what was thought to be such, was found in stomachs taken from June to September, inclusive. It was eaten regularly and moderately, and the total for the season was 3.74 per cent of the whole food. Wild fruits or berries of 22 species were found in 72 stomachs, distributed through every month of the bird's stay at the north. Beginning with 1.18 per cent in April, the quantity gradually increases to 87.17 per cent in October, when it makes more than five-sixths of the whole food. The average for the season is 33.51 per cent. In this investigation Rubus seeds (blackberries or raspberries) are always reckoned as cultivated fruit, though probably most often wild. Besides fruit, a few seeds and rose haws were found, which with a little rubbish complete the vegetable food (40.41 per cent).
Following is a list of fruits, seeds, etc., identified and the number of stomachs in which found:
| Yew berries (Taxus minor)1 False Solomon's seal (Smilacina racemosa)1 Bayberries (Myrica carolinensis)1 Mulberries (Morus sp.)10 Spiceberries (Benzoin æstivale)5 Currants (Ribes sp.)1 Mountain ash (Pyrus americanus)2 Service berries (Amelanchier canadensis)2 Blackberries or raspberries (Rubus sp.)17 Rose haws (Rosa sp.)1 Wild black cherries (Prunus serotina)1 Chokecherries (Prunus virginiana)7 Domestic cherries (Prunus cerasus)4 Croton (Croton sp.)1 | American holly (Ilex opaca)2 Woodbine berries (Psedera quinquefolia)1 Frost grapes (Vitis cordifolia)4 Wild sarsaparilla (Aralia nudicaulis)1 Flowering dogwood (Cornus florida)3 Rough-leaved cornel (Cornus asperifolia)4 Dogwood (Cornus sp.)1 Black gum (Nyssa sylvatica)1 Huckleberries (Gaylussacia sp.)1 Blueberries (Vaccinium sp.)6 French mulberry (Callicarpa americana)1 Black elderberries (Sambucus canadensis)1 Other elderberries (Sambucus sp.)3 Fruit pulp not further identified12 |
| Yew berries (Taxus minor) | 1 |
| False Solomon's seal (Smilacina racemosa) | 1 |
| Bayberries (Myrica carolinensis) | 1 |
| Mulberries (Morus sp.) | 10 |
| Spiceberries (Benzoin æstivale) | 5 |
| Currants (Ribes sp.) | 1 |
| Mountain ash (Pyrus americanus) | 2 |
| Service berries (Amelanchier canadensis) | 2 |
| Blackberries or raspberries (Rubus sp.) | 17 |
| Rose haws (Rosa sp.) | 1 |
| Wild black cherries (Prunus serotina) | 1 |
| Chokecherries (Prunus virginiana) | 7 |
| Domestic cherries (Prunus cerasus) | 4 |
| Croton (Croton sp.) | 1 |
| American holly (Ilex opaca) | 2 |
| Woodbine berries (Psedera quinquefolia) | 1 |
| Frost grapes (Vitis cordifolia) | 4 |
| Wild sarsaparilla (Aralia nudicaulis) | 1 |
| Flowering dogwood (Cornus florida) | 3 |
| Rough-leaved cornel (Cornus asperifolia) | 4 |
| Dogwood (Cornus sp.) | 1 |
| Black gum (Nyssa sylvatica) | 1 |
| Huckleberries (Gaylussacia sp.) | 1 |
| Blueberries (Vaccinium sp.) | 6 |
| French mulberry (Callicarpa americana) | 1 |
| Black elderberries (Sambucus canadensis) | 1 |
| Other elderberries (Sambucus sp.) | 3 |
| Fruit pulp not further identified | 12 |
Of the two stomachs not included in the foregoing discussion, the one taken in Florida in January contained 93 per cent of wild fruit and 7 per cent of weevils, wasps, and spiders; the one collected in Alabama in February was entirely filled with animal food, of which 88 per cent was caterpillars, 5 per cent May beetles, 6 per cent bugs, and 1 per cent spiders.