28 BORNED LABKfi IN RELATION TO AGRICULTURE. 
MINERAL MAI' IKK. 
Horned larks use a very large amount of gravel to assist in grinding 
their food, and. strange as it may seem, nestlings have more of it. in 
their stomachs than adult-. Five stomachs of nestlings which con- 
tained no food material except of an animal nature held an average of 
2] percent of gravel. Now. it has been supposed, since granivorous 
birds usually eat much gravel, and since exclusively insectivorous 
birds, such as cuckoos, take almost none, that its function i» the crush- 
ing and grinding of seeds to aid in their digestion. Hut why the thin- 
walled stomach of fledglings which are fed almost exclusively on soft 
animal foods should contain 80 much gravel is a question for which no 
satisfactory answer has yet been found. The percentage for the nest- 
lings is 21.8, for the adults Is. 4. and for the birds in first plumage 
14.1*. The last group is the most vegetarian of the three, but, oddly 
enough, takes the least grinding material. The mineral matter con- 
sists principally of coarse and fine sand, sandstone, quartz, and cinders. 
Many hits of fossils were found, among which were fragments of 
foraminifera. brachipods, sea urchins, corals, bryozoans, and crinoids. 
NESTLING AND OTHER YOUNG HORNED LARKS. 
As with most of our common birds, nestlings of the horned larks are 
more insectivorous than older individuals, although while still in the 
nest they are sometimes U i d considerable vegetable matter. From the 
present investigation the ratio of vegetable to animal food is found to 
be L6.3 to s:;.T. 
A thorough study of the diet of the nest line- larks requires a larger 
amount of material than is available. 'Fen stomachs have been exam- 
ined, which were taken in three States, from April to July, inclusive. 
Those obtained early in the season, and from northern States, contained 
the largest amounts of vegetable matter. Of these, three contained 1, 
8, and 4<» percent, respectively, and two 50 percent, of vegetable sub- 
stances. A nestling taken in April in New York had been \'vd 4:5 per- 
cent of wheat. This consisted of whole grains, which would seem to 
he rather unsuitable food for a fledgling. The other vegetable matter 
found in the stomachs of nestling larks was mainly weed seeds. Among 
them were green foxtail (Chxtochloa viridis)^ tumbleweed (Amaran- 
///'/.s). and yellow sorrel (Oasalis stricta). 
In th<- animal matter were wireworms ( Elati /•/<//'), other beetle larvae, 
mainly w hite grubs ( Scaraba ida ). adult hectics, such as scarabseids, leaf 
hectics (Chrysomelidae), pill hectics {Byrrhidai), and weevils (Rhyn- 
chophora). The latter were found in all but three of the stomachs and 
formed 16.3 percent of the total food of the nestlings. Of the chrys- 
omelids, one stomach contained fragments of at least 50 individuals 
