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 nestlings, 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 larve 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. 
