52 



BULLETIN 107, U. S. DEPARTMENT OF AGRICULTURE. 



Stomach analysis of these birds also revealed the fact that the 

 value of the young English sparrow as a weevil destroyer varies con- 

 siderably and rapidly as his nestling life progresses. From the 

 blind, naked, and helpless bird of a day or two, which must neces- 

 sarily be fed on the softest and most easily assimilated foods, as 

 weevil Iarva3, caterpillars, spiders, etc., to the lusty-lunged fledgling, 

 whose food is characterized by grain and hard-shelled insects, differ- 

 ing but little from that of the adult, we find all intermediate stages. 

 That some idea may be given of the proportion of the several prin- 

 cipal food items found to occur at various stages of the nestling's 

 life, the writer has arranged the material into four groups which 

 represent as nearly as possible birds of the first, second, third, and 

 fourth quarters, respectively, of the nestling life. Six of the prin- 

 cipal food items, namely, alfalfa weevils, ground beetles, caterpillars, 

 flies, spiders, and grain, are considered in showing the change of food 

 habits as life progresses, and these are illustrated in figure 3. Or- 

 thoptera (grasshoppers) form an important article of food late in 

 the season and would have been included had field work been con- 

 tinued until fall. These insects, especially the nymphs, were eaten 

 extensively by nestlings of the first and second quarter during July. 

 The following tabulation shows the changing percentages of foods 

 during the four quarters of nestling life : 



As the bird becomes older there is a gradual decrease in the con- 

 sumption of weevils, as well as of other soft and easily digested foods, 

 as caterpillars, flies, and spiders, while the hard-shelled ground beetles 

 are taken in greater quantity. Grain, mostly wheat, early becomes 

 an important food item, and by the time the bird has left the nest it 

 is well fitted to uphold the reputation of its parents. 



FIELD OBSERVATIONS ON THE FEEDING OF NESTLINGS. 



Observations also were made of the amount of food given the 

 young English sparrows and the frequency of the feedings. Parent 

 birds were timed for a period, usually an hour, and at the end of this 

 time the incoming bird was captured and the contents of its bill and 

 throat recorded. By taking the average of a number of such obser- 

 vations the writer was able to get a fair idea of the amount of food 

 consumed daily by a nest of these young birds. 



