Birds of the titmouse family, though insignificant in size, are far from
being so in the matter of food habits. What they lack in size of body
they more than make up in numbers of individuals. While in the case of
some larger birds, as, for instance, the flicker, there is one pair of
eyes to look for food for one large stomach, we have in the case of the
ten times as numerous titmice an equivalent stomach capacity divided into
10 parts, each furnished with a pair of eyes and other accessories, as
wings and feet. As against the one place occupied by the larger bird, 10
are being searched for food at the same time by the smaller species.
The character of the food of titmice gives a peculiar value to their
services, for it consists largely of the small insects and their eggs
that wholly escape the search of larger birds. Throughout the year most
of the species of this group remain on their range, so that they are
constantly engaged in their beneficial work, continuing it in winter when
the majority of their coworkers have sought a milder clime. It is at
this season that the titmice do their greatest good, for when flying and
crawling insects are no more to be found, the birds must feed upon such
species as they find hibernating in crevices, or upon the eggs of insects
laid in similar places. In winter's dearth of moving insects the search
for such animal food as may be found is perforce thorough and unremitting.
Within the boundaries of the United States are some 17 species of
titmice, with nearly as many races or subspecies, so that there is
no portion of the country lacking one or more forms. The western
coast region is peculiarly rich In representatives of the family. In
the eastern portion of the country the best-known and most widely
distributed species is the common black-capped chickadee[8] (fig. 3).
This bird, or some of its subspecies, occupies the whole of that part of
the United States north of the latitude of Washington and extends into
Canada. It is a prolific breeder, usually rearing from six to eight young
in a brood.
[8] _Penthestes atricapillus_.
[Illustration: Fig. 3.--Black-capped chickadee. Length, about 5¼
inches.]
Examination of 289 stomachs of this chickadee shows that its food
consists of 68 per cent animal matter (insects) and 32 per cent vegetable
matter. The former is made up of small caterpillars and moths and their
eggs. Prominent among the latter are the eggs of the tent caterpillar
moths, both the orchard and forest species. As these are two of our most
destructive insects, the good done by the chickadee in devouring their
eggs needs no comment. During the winter the chickadee's food is made
up of larvæ, chrysalids, and eggs of moths, varied by a few seeds, but
as spring brings out hordes of flying, crawling, and jumping insects,
the bird varies its diet by taking also some of these. Flies and bugs
are the favorites until the weather becomes quite warm, when beetles and
small wasps also are enjoyed. Among the bugs may be mentioned the plant
lice and their eggs which are eaten in winter. The beetles nearly all
belong to the group of snout beetles, more commonly known as weevils.
These insects are mostly of small size, and nearly all are known to the
farmer or fruit raiser as pests. Seventeen of them were found in one
stomach. Grasshoppers do not at any time constitute an important element
of the food of the chickadee, as they are too large for so small a bird;
moreover, they are for the most part terrestrial Insects, while the bird
is essentially arboreal. Small wasps and ants are eaten to some extent
Spiders constitute an Important element of the food and are eaten at all
times of the year, the birds locating them when they are hibernating in
winter, as well as when they are active in summer. The vegetable food of
the chickadee consists largely of small seeds, except in summer, when
they are replaced by pulp of wild fruit. The wax from the seeds of poison
ivy Is eaten during the winter months, but the seeds themselves are not
taken. In this respect the chickadee differs from most other birds, which
swallow the seeds whole; these, after digesting the wax, pass the seeds
through the alimentary canal, or regurgitate them, and so scatter them
broadcast to reproduce the noxious plants.
In the southern part of the country the Carolina chickadee[9] and the
tufted tit[10] replace the black-cap, but their food habits are so
similar that there is practically no difference in the work done. In the
West several other species occur; one of the most interesting is the
bush tit[11] which, with several subspecies, occupies the whole Pacific
coast region. They are active, social little creatures, and except for a
short time during the breeding season are found in flocks, flitting from
tree to tree, busily hunting for Insects and their eggs. The contents
of 66 stomachs of these birds were found to consist mostly of injurious
insects to the extent of 83 per cent. Of these the most important was a
small hemipterous insect which amounted to more than half of the stomach
contents. These insects are of considerable economic importance, as they
frequently infest grapevines and other plants to a harmful extent Several
stomachs were almost exclusively filled with these minute creatures, some
containing as many as 100 individuals.
[9] _Penthestes carolinensis_.
[10] _Bæolophus bicolor_.
[11] _Psaltriparus minimus_.
Perhaps the most important and interesting insect found was the black
olive scale, which occurred in 24 stomachs and amounted to a little more
than 18 per cent of the food. In addition, a number of the stomachs were
more or less filled with another scale, which was not further identified.
A number of small snout beetles (weevils) were eaten and some small
caterpillars; there were also the remains of a spider.
The vegetable food of the species seemed to consist mostly of seeds, but
they were so broken up as to defy recognition. A little fruit pulp and a
little mast were also found.
Among the stomachs of the bush tits examined were those of one brood
of eight nestlings about 10 days old. The vegetable matter in these
stomachs was only three-fourths of 1 per cent and consisted of one seed
and some rubbish. The animal matter was made up of beetles, wasps, bugs,
caterpillars and pupæ, and spiders. The greatest interest lies in the
fact that every one of these stomachs contained pupæ of the codling
moth, on an average of over five to each. The oak tree in which these
birds were found was in a belt of timber near a neglected orchard which
the parent birds used as a foraging ground, and they did their best to
remedy the neglect of the owner. As feeding and digestion in the case of
nestling birds is almost continuous during the hours of daylight, the
above record would be several times repeated during a day's feeding.
There were probably not less than a dozen nests of the bush tit along
the border of this orchard, and these birds must have exerted a great
restrictive influence upon the increase of the codling moth, as well as
of other insects in that vicinity.