54 BULLETIN 107, U. S. DEPARTMENT OF AGRICULTURE. 



Another series of observations gave an average of 5 minutes 

 between the feedings. The female in this case carried a ground 

 beetle (Harpalus amputatus], a caterpillar, and 9 larvae of the 

 alfalfa weevil in her bill and throat. 



Observations of feeding of nestlings on an unoccupied farm showed 

 that visits were made at the rate of IT trips an hour, or about one 

 trip every 3J minutes. The female was carrying 28 larva? of the 

 weevil on her last trip. 



From this series of five observations it appears that the parent 

 English sparrows visited their nest on an average of about once 

 every 5J minutes, or a little more than 11 trips an hour. The four 

 adults captured had as food for their young 2 kernels of wheat; 

 IT alfalfa weevil larvae ; 1 ground beetle, 9 weevil larva? and a cater- 

 pillar; and 28 weevil larva?, respective!} 7 . Three other adults taken 

 in the fields had food for nestlings in their bills. This amounted to 

 18 weevil larva? and an aphid in the first, 5 larva? in the second, and 

 3 coccinellid larva?, 13 weevil larva?, and 2 pupa? in the third. 



Though this is a rather heterogeneous assortment, it would appear 

 that 15 larvae of the weevil or their equivalent in bulk of other insects 

 would be a fair estimate of an average amount of food brought in at 

 each trip by adult birds. In fact, it is certain that the material 

 brought in frequently greatly exceeded this amount. 



Allowing, then, 15 larva? at each trip and 11 trips per hour, these 

 birds would bring in 165 larvae per hour. Then, assuming that the 

 young were being fed for 12 hours each day, a conservative estimate, 

 we would have a total of 1,980 larva? consumed by one brood in one 

 day. As previously stated, straw-thatched sheds containing upward 

 of 100 nest holes, both old and new, are frequent, and it is not uncom- 

 mon to find farmyards where this number of nests are occupied. 

 There are also ample nesting sites about the other buildings and in 

 the ever-present Lombardy poplar, cottonwood, or box elder. Such 

 a colony of birds would devour a daily total of 198,000 larva?, or an 

 equivalent bulk in other food. As the young birds remain in the nest 

 for at least 10 days and are probably fed several days longer by the 

 adults, they will have eaten food equivalent to the bulk of 1,980,000 

 larva? during their nestling life. 



As these birds are not feeding exclusively on this insect, the aver- 

 age amount of weevils eaten by young English sparrows during the 

 height of the season being about 25 per cent of their food, under 

 average conditions we would have the young of such a colony eating 

 495,000 weevils. While there may be some farms where only com- 

 paratively few larvae are eaten, there must be others where favorable 

 circumstances will bring the total destroyed by the nestlings of one 

 brood nearer the larger figure. 



