NESTLING CARDINALS. 23 



Mineral Matter. 



Mineral matter taken for grinding purposes, among which were 

 many bits of cinder in addition to the usual quartz fragments and 

 sand, averaged 5.7 percent of the gross contents of the stomachs 

 examined. 



Nestlings. 



The nestlings of the cardinal, in common with those of most birds, 

 are highly insectivorous. During the preparation of this report 4 

 have been examined, with the result that 94.75 percent of their food 

 was found to be animal matter and 5.25 vegetable. Two of the num- 

 ber were young, just out of the nest, and they had consumed the 

 vegetable substances; 2 were nestlijags, and their diet was en- 

 tirely animal. The stomach of one of the latter contained the 

 thorax of a large cicada, and that of the other the remaining por- 

 tions of that luckless insect. Both had been fed caterpillars — 

 purslane (fig. 38) and laurel sphinxes — and each, contained grass- 

 hoppers and spiders. A few larva? and eggs of other insects also 

 were in their stomachs. One of the young, just out of the nest, had 

 been given a cicada, and, in addition, some 9 grasshoppers, a snail, 

 and a few seeds, while the other had eaten lamellicorn beetles, weevils, 

 and blackberry seeds. The proportions of the principal food items 

 of the four nestlings are as follows: Cicadas, 17.25 percent; grass- 

 hoppers, 20 ; caterpillars, 21.25 ; and beetles, 23.25. Two other fledge- 

 lings in the collection had only a few bits of snail in their stomachs. 



Observations upon nestling birds in the field being recognized as 

 valuable in supplementing data obtained from the examination of 

 stomachs, an effort was made throughout the season of 1906 to locate 

 and thoroughly study a grosbeak family. Owing to various vicissi- 

 tudes, satisfactory observations were made upon only one nest. Fifty- 

 six trips by the parents were made to this nest in six and one-half 

 hours, an average of 8.6 an hour. The young were fed 178 times, an 

 average of 89 each. The longest interval between visits was thirty- 

 five minutes, the shortest two. 



The character of the food could not be determined by observation, 

 but it was learned in another way. None of the excrement was re- 

 moved from the box, whereas the nest in which the youngsters had 

 been reared was kept perfectly clean. The fecal matter was dried and 

 examined, and while by no means all of its constituents could be 

 identified, enough was learned to indicate that the study of excreta is 

 a very satisfactory method of determining the food of nestling birds. 

 The nest of any fairly bold bird may be kept under surveillance and 

 the waste matter collected before the parents remove it. The extent 

 of the information as to the food eaten by the young to be obtained in 

 this way is astonishing. 



