FOOD OF SPARROWS. 
The following conclusions upon the relations of sparrows to agri- 
culture are based upon the study of the food habits of a score of 
species, 1 and have involved the examination of the contents of the 
stomachs of more than 4,000 individuals. These stomachs were col- 
lected during every month in the year from a large expanse of country, 
including practically all the States in the Union and the southern 
part of the Dominion of Canada. 
MINERAL SUBSTANCES FOUND IN SPARROWS' STOMACHS. 
Mineral matter plays a part in the digestion of sparrows and often 
amounts to one-tenth or one-quarter of the total contents of a stomach. 
These birds are preeminently seed eaters. Insectivorous birds with 
soft, weak bills and thin membranous stomachs could not possibly 
eat and digest a meal of tough, resisting seeds; but the hard, strong 
beaks and powerful, muscular gizzards of sparrows are admirably 
adapted to such a diet. Sparrows swallow the smaller seeds whole, 
but crack the larger ones. To aid digestion they pick up, while feed- 
ing, coarse bits of sand and tiny stones, which, in their mill-like giz- 
zards, soon grind the seed material into 
a paste that can be as easily digested 
and assimilated as if it had been chewed 
by teeth. This mineral matter usually 
consists of angular white or pink peb- 
bles of quartz from 2 to 5 mm. in diame- 
ter. Pieces of feldspar, tourmaline, 
mica, and even volcanic lava are some- 
times found, and in Kansas the birds 
often utilize the disk-like sections of 
stems of fossil sea-lilies (Crinoidea — 
see fig. 10). A sooty grouse taken in British Columbia had swallowed 
for this purpose four little nuggets of gold. 2 
FOOD IN GENERAL. 
Of the food of sparrows, animal matter composes from 25 to 35 per- 
cent of the diet for the entire year, and vegetable matter from 65 
to 75 percent. The animal food consists of insects and spiders and 
1 The remainder of the native sparrows, which are mostly birds of more or less 
limited numbers or restricted distribution, are not considered in this bulletin, 
owing to lack of material for adequate study. 
* Forest and Stream. Vol. XXXIV. p. 431, 1890. 
19 
Fig. 10.— Section of stem of fossil sea- 
lily. 
