Food Habits of the Thrushes of the United States Part 2

_Vegetable food._--A few _Rubus_ seeds were recorded as cultivated fruit, but they were found in only two stomachs and probably were wild, as the gray-cheeked thrush does not live where it is likely to come in contact with cultivated blackberries or raspberries. In any case they amount to only 0.15 per cent. Wild fruits of 18 different species (23.98 per cent) make up nearly one-fourth of the whole food--in fact, the vegetable food, other than wild fruit, is insignificant. Wild berries supplement the regular food, which consists of insects and spiders.

The following list shows the fruits and seeds identified and the number of stomachs in which found:

False spikenard (_Smilacina racemosa_) 1 Greenbrier berries (_Smilax_ sp.) 2 Bayberries (_Myrica carolinensis_) 1 Poke berries (_Phytolacca decandra_) 2 Crab apples (_Pyrus_ sp.) 1 Wild black cherries (_Prunus serotina_) 5 Blackberries or raspberries (_Rubus_ sp.) 2 Sumac berries (_Rhus_ sp.) 1 Black-alder berries (_Ilex verticillata_) 1 Wild grapes (_Vitis_ sp.) 5 Wild sarsaparilla (_Aralia_ sp.) 1 Flowering dogwood (_Cornus florida_) 5 Rough-leaved dogwood (_Cornus asperifolia_) 2 White cornel (_Cornus candidissima_) 1 Dogwood (_Cornus_ sp.) 1 Sour gum (_Nyssa sylvatica_) 2 Black nightshade (_Solanum nigrum_) 1 Dockmackie (_Viburnum acerifolium_) 1 Arrowwood (_Viburnum_ sp.) 1 Elderberries (_Sambucus canadensis_) 3 Fruit not further identified 6

_Summary._--In the food of the gray-cheeked thrush the only useful element is a small percentage (2.83) of useful beetles. The remainder of the animal food is composed of either harmful or neutral elements.

The vegetable food, drawn entirely from nature's great storehouse, contains no product of human industry, either of grain or fruit.

Whatever the sentimental reasons for protecting this bird, the economic ones are equally valid.

OLIVE-BACKED AND RUSSET-BACKED THRUSHES.

(_Hylocichla ustulata swainsoni_ and _Hylocichla ustulata ustulata_.)

The olive-backed thrush and its relative, the russet-backed, occupy the whole of the United States at some time during the year. The olive-back breeds north of our northern border, except in the higher mountains, and the russet-back on the Pacific coast nests as far south as southern California. The habits of birds of this species resemble those of others of the genus in living in swamps and woodlands rather than in gardens and orchards. The russet-back on the Pacific coast, however, seems to have become quite domestic, and wherever a stream runs through or past an orchard or garden, or the orchard is near thick chaparral, this bird is sure to be found taking its toll of the fruit and rearing its young in the thicket beside the stream. During the cherry season it takes a liberal share of the fruit, but its young, then in the nest, are fed almost entirely on insects. The eastern subspecies, on the contrary, does not come in contact with domestic fruit or any other product of husbandry. A great number of the subspecies nest far north of the region of fruit raising.

For this investigation 403 stomachs of the olive-backed thrush were available, collected in 25 States, the District of Columbia, and Canada. Florida, Louisiana, and Texas represent the most southern collections and New Brunswick, Ontario, and Northwest Territory the most northern. In California 157 stomachs were obtained, which, with those taken in Oregon and Was.h.i.+ngton, fairly represent the Pacific coast region. The whole collection was fairly well distributed over the nine months from March to November. The food consisted of 63.52 per cent of animal matter to 36.48 per cent of vegetable.

_Animal food._--Beetles of all kinds amount to 16.29 per cent. Of these 3.14 per cent are the useful Carabidae. The others belong to harmful or neutral families. Weevils or snout-beetles (Rhynchophora) amount to 5.29 per cent, a high percentage for such insects. One Colorado potato beetle (_Leptinotarsa decemlineata_) was found in a stomach taken on Long Island. Hymenoptera collectively aggregate 21.50 per cent. Of these, 15.20 per cent are ants--a favorite food of _Hylocichla_. The remainder (6.30 per cent) were wild bees and wasps.

No honeybees were found. Caterpillars, which rank next in importance in the food of the olive-back, form a good percentage of the food of every month represented and aggregate 10.30 per cent for the season.

Gra.s.shoppers are not an important element in the food of thrushes, as they chiefly inhabit open areas, while _Hylocichla_ prefers thick damp cover, where gra.s.shoppers are not found. An inspection of the record shows that most of the orthopterous food taken by the olive-back consists of crickets, whose habits are widely different from those of gra.s.shoppers, and which are found under stones, old logs, or dead herbage. The greatest quant.i.ty is taken in August and September. The average for the season is 2.42 per cent.

Diptera (flies) reach the rather surprisingly large figure of 6.23 per cent. These insects are usually not eaten to any great extent except by flycatchers and swallows, which take their food upon the wing. The flies eaten by the olive-back are mostly crane flies (Tipulidae) or March flies (_Bibio_), both in the adult and larval state. Crane flies are slow of wing and frequent shady places. The larvae of both groups are developed in moist ground, and often in colonies of several hundred. With these habits it is not surprising that they fall an easy prey to the thrushes.

Hemiptera (bugs), a small but rather constant element of the food, were found in the stomachs collected every month, and in July reach 11.11 per cent. They were of the families of stinkbugs (Pentatomidae), s.h.i.+eld bugs (Scutelleridae), tree hoppers (Membracidae), leaf hoppers (Ja.s.sidae), and cicadas. Some scales were found in one stomach. The total for the season is 3.76 per cent. A few insects not included in any of the foregoing categories make up 0.48 per cent of the food.

Spiders, with a few millipeds, amount to 2.22 per cent, the lowest figure for this item of any bird of the genus _Hylocichla_. Snails, sowbugs, angleworms, etc. (0.32 per cent), complete the animal food.

Following is a list of insects identified and the number of stomachs in which found:

HYMENOPTERA.

_Camponotus pennsylvanicus_ 1 _Tiphia inornata_ 1

COLEOPTERA.

_Cychrus nitidicollis_ 1 _Cychrus stenostomus_ 1 _Notiophilus aeneus_ 1 _Pterostichus sayi_ 1 _Pterotichus l.u.s.trans_ 1 _Amara interst.i.tialis_ 1 _Triaena longula_ 1 _Agonoderus pallipes_ 1 _Silpha ramosa_ 1 _Staphylinus cinnamopterus_ 1 _Tachyporus californicus_ 1 _Chilocorus...o...b..s_ 1 _Scymnus_ sp 1 _Hister america.n.u.s_ 1 _Ips quadriguttatus_ 4 _Cytilus sericeus_ 1 _Agriotes stabilis_ 1 _Podabrus flavicollis_ 2 _Podabrus modestus_ 2 _Silis lutea_ 1 _Telephorus carolinus_ 1 _Telephorus bilineatus_ 5 _Telephorus divisus_ 2 _Onthophagus hecate_ 1 _Onthophagus striatulus_ 1 _Onthophagus tuberculifrons_ 2 _Onthophagus_ sp 4 _Ataenius abditus_ 1 _Aphodius hamatus_ 1 _Aphodius fimetarius_ 6 _Aphodius inquinatus_ 7 _Aphodius_ sp 6 _Geotrupes_ sp 1 _Dichelonycha elongata_ 2 _Lachnosterna hirticula_ 1 _Lachnosterna_ sp 12 _Anomala undulata_ 1 _Anomala_ sp 1 _Euphoria fulgida_ 1 _Donacia emarginata_ 1 _Haemonia nigricornis_ 1 _Syneta pallida_ 1 _Leptinotarsa decemlineata_ 1 _Gastroidea_ sp 1 _Galerucella decora_ 1 _Diabrotica soror_ 1 _Diabrotica_ sp 1 _Gonioctena pallida_ 1 _Luperodes bivittatus_ 1 _Opatrinus notus_ 1 _Blapstinus metallicus_ 1 _Blapstinus maestus_ 1 _Blapstinus_ sp 1 _Otiorhynchus ovatus_ 1 _Thinoxenus_ sp 1 _Cercopeus chrysorrhaeus_ 1 _Barypithes pellucidus_ 1 _Sitones flavescens_ 1 _Sitones_ sp 1 _Phytonomus punctatus_ 2 _Pachylobius picivorus_ 1 _Conotrachelus posticatus_ 1 _Micromastus elegans_ 1 _Acalles clavatus_ 1 _Cryptorhynchus bisignatus_ 1 _Rhinoncus pyrrhopus_ 1 _Balaninus_ sp 3 _Sphenophorus parvulus_ 1 _Sphenophorus_ sp 1 _Scolytus muticus_ 1

LEPIDOPTERA.

_Edema albifrons_ 1

TRICHOPTERA.

_Phryganea californica_ 1

HEMIPTERA.

_Myodocha serripes_ 1 _Sinea diadema_ 1

This list of insects contains a considerable number of injurious species and some that at various times and places have become decided pests. Such are the Colorado potato beetle (_Leptinotarsa decemlineata_), the spotted squash beetle (_Diabrotica soror_), the cloverleaf weevil (_Phytonomus punctatus_), and the various species of _Lachnosterna_, the parent of the destructive white grubs. Many others are plant feeders and may increase to such an extent as to inflict great damage upon agriculture.

_Vegetable food._--The vegetable food of the olive-backed thrush consists of small fruit. The bird has a weak bill and can not break through the tough skin of the larger kinds. In the cherry orchards of California the writer many times observed the western subspecies of this bird, the russet-back, on the ground pecking at cherries that had been bitten open and dropped by linnets and grosbeaks. Blackberries and raspberries have a very delicate skin and are successfully managed by weak-billed birds, so that all the records of domestic fruit eaten by the eastern form relate to these berries, and it is probable that in most cases the fruit was not cultivated. The total of cultivated fruit for the season is 12.63 per cent of the whole food, but if we consider the eastern subspecies alone this item would practically disappear. Wild fruit (19.73 per cent) is eaten regularly and in a goodly quant.i.ty in every month after April. Weed seeds and a few miscellaneous items of vegetable food (4.04 per cent) close the account.

Following is a list of vegetable foods so far as identified and the number of stomachs in which found.

White cedar seeds (_Thuja occidentalis_) 1 Red cedar berries (_Juniperus communis_) 2 False Solomon's seal (_Smilacina trifolia_) 3 Greenbrier (_Smilax tamnifolia_) 1 Cat brier (_Smilax_ sp.) 1 Hackberry (_Celtis occidentalis_) 3 Mulberry (_Morus_ sp.) 2 Fig (_Ficus_ sp.) 3 Pale persicaria (_Polygonum lapathifolium_) 1 Poke berries (_Phytolacca decandra_) 9 Mountain ash (_Pyrus americana_) 1 Service berries (_Amelanchier_ sp.) 1 Blackberries or raspberries (_Rubus_ sp.) 67 Rose haws (_Rosa_ sp.) 1 Wild black cherries (_Prunus serotina_) 15 Bird cherries (_Prunus Pennsylvanica_) 2 Domestic cherries (_Prunus cerasus_) 29 Domestic plum (_Prunus domestica_) 2 Apricot (_Prunus armeniaca_) 3 Filaree (_Erodium_ sp.) 1 Poison oak (_Rhus diversiloba_) 4 Staghorn sumac (_Rhus hirta_) 2 Dwarf sumac (_Rhus copallina_) 3 Other sumac (_Rhus_ sp.) 4 Pepper tree (_Schinus molle_) 1 American holly (_Ilex opaca_) 1 Black alder (_Ilex verticillata_) 1 Coffee berries (_Rhamnus californicus_) 3 Woodbine (_Psedera quinquefolia_) 10 Frost grape (_Vitis cordifolia_) 6 Spikenard (_Aralia racemosa_) 2 Flowering dogwood (_Cornus florida_) 7 Kinnikinnik (_Cornus amomum_) 2 Red osier (_Cornus stolonifera_) 1 Panicled cornel (_Cornus paniculata_) 3 Dogwood unidentified (_Cornus_ sp.) 6 Huckleberries (_Gaylussacia_ sp.) 1 Three-flowered nightshade (_Solanum triflorum_) 1 Nightshade unidentified (_Solanum_ sp.) 8 Black twinberries (_Lonicera involucrata_) 2 Honeysuckle berries (_Lonicera_ sp.) 2 s...o...b..rries (_Symphoricarpos racemosus_) 2 Dockmackie (_Viburnum acerifolium_) 1 Arrowwood (_Viburnum_ sp.) 1 Black elderberries (_Sambucus canadensis_) 6 Red elderberries (_Sambucus p.u.b.ens_) 5 Blue elderberries (_Sambucus glauca_) 15 Tarweed (_Madia_ sp.) 1 Fruit pulp not further identified 17

_Food of young of russet-backed thrush._--Before concluding the discussion of this species it will be of interest to note the results obtained from an investigation of stomachs of 25 nestlings of the russet-back taken in June and July when the birds were from two to eleven days old. These were from eight broods, ranging from three to five nestlings to the brood. The percentage of animal food of the young (92.60 per cent) is considerably higher than that of the parent birds.

The distribution of the animal food is as follows: Caterpillars were found in every stomach but seven and aggregated nearly 27 per cent; beetles, including the useful Carabidae (7.7 per cent), are irregularly distributed to the extent of 22 per cent; other more or less harmful species included five families of (Hemiptera) bugs, 13.8 per cent, viz, stinkbugs, leaf hoppers, tree hoppers, s.h.i.+eld bugs, and cicadas; ants and a few other Hymenoptera amount to 12 per cent, and spiders the same. These latter were mostly harvestmen or daddy longlegs (Phalangidae). The remainder (6 per cent) included a few miscellaneous insects. Only three stomachs contained remains of gra.s.shoppers.

Carabid beetles were eaten by the young birds to the extent of 7.7 per cent, which is more than three times the amount eaten by the adults, a remarkable fact when is considered that these insects are very hard sh.e.l.led, thus seemingly unsuited for young birds.

The vegetable food consisted of fruit (6.8 per cent), mainly blackberries or raspberries, found in 11 stomachs, and twinberries in 1, and two or three other items, including a seed of filaree and some rubbish. From the irregular variety of food in the different stomachs, it would seem that the parents make little selection, but fill the gaping mouths of their young with the nearest obtainable supply.

In addition to the examination of stomach contents of nestlings two nests were carefully and regularly watched, and from these it was determined that the parent birds fed each nestling 48 times in 14 hours of daylight. This means 144 feedings as a day's work for the parents for a brood of three nestlings, and that each stomach was filled to its full capacity several times daily, an ill.u.s.tration that the digestion and a.s.similation of birds, especially the young, are constant and very rapid. Experiments in raising young birds have proved that they thrive best when fed small quant.i.ties at short intervals rather than greater quant.i.ties at longer periods. Aside from the insects consumed by the parents, a brood of three young birds will thus each require the destruction of at least 144 insects in a day and probably a very much greater number.

_Summary._--In a resume of the food of the olive-backed and russet-backed thrushes one is impressed with the fact that they come in contact with the products of industry but rarely. The olive-back's food habits infringe upon the dominion of man but little. The bird lives among men, but not with them. The western form, the russet-back, comes more into relations with the cultivated products because it visits orchards and partakes freely of the fruit. Even then the damage is slight, as much of the fruit eaten is that fallen to the ground.

Moreover, while the adult bird is feeding upon fruit a nestful of young are being reared upon insects which must be largely taken from the orchard, thus not only squaring the account but probably overbalancing it in favor of the farmer.

HERMIT THRUSHES.

(_Hylocichla guttata_ subspp.)

The hermit thrush of the subspecies _H. g. pallasi_ inhabits the Eastern States in winter as far north as Ma.s.sachusetts and breeds from the mountains of Maryland and Pennsylvania and from northern Michigan and central Minnesota northward to Alaska. Several other subspecies occupy the Pacific coast region in suitable localities--that is, in the higher and more wooded sections, as this bird, like all of the genus _Hylocichla_, does not live in treeless or arid regions. In the East the bird is a late fall migrant and may often be seen sitting silent and alone on a branch in the forest in late October or even in November, when the great army of migrants have pa.s.sed on to the South.

While a beautiful songster, the species is so quiet and un.o.btrusive that by sight it is entirely unknown to many.

Inquiry into the food habits of this bird covered 551 stomachs, collected in 29 States, the District of Columbia, and Canada, and representing every month of the year, though all the stomachs taken in winter were collected in the Southern States, the District of Columbia, and California. In the primary a.n.a.lysis the food was found to consist of 64.51 per cent of animal matter to 35.49 per cent of vegetable. The former is mostly composed of insects with some spiders, while the latter is largely fruit, chiefly wild species.

_Animal food._--Beetles const.i.tute 15.13 per cent of the food. Of these 2.98 per cent are of the useful family, Carabidae. The remainder are mostly harmful. Scarabaeidae, the larvae of which are the white grubs that destroy the roots of so many plants, were eaten to the extent of 3.44 per cent. Snout beetles, among the most harmful of insects, were taken to the extent of 3.13 per cent. Among these was the notorious plum curculio (_Conotrachelus nenuphar_) found in two stomachs taken in the District of Columbia in April of different years. Two other species of the same genus also were found, as well as the clover weevil (_Epicaerus imbricatus_). The Colorado potato beetle (_Leptinotarsa decemlineata_) and the striped squash beetle (_Diabrotica vittata_), with a number of other species of less notoriety, were found in several stomachs. Thus, in spite of the bird's retiring habits, it comes in contact with some of the pests of cultivation.

[Ill.u.s.tration: B2085-73

Fig. 2.--Hermit thrush (_Hylocichla guttata_).]