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,^ 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 SPARROVV^S' 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 tin}^ 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,^ 



Fig. 10.— Section of stem of fossil sea- 

 lily. 



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 



^ 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. 



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