10 
Conservation Bulletin 18 
most numerous. Besides the insects already mentioned, many wasps and bugs 
are taken. Predacious and parasitic liymenopterous insects and predacious 
beetles, all useful, are eaten only to a slight extent, so that as a whole the insect 
diet of the native sparrows may be considered beneficial. There are several 
records of potato-bug larvae eaten by chipping sparrows. 
Their vegetable food is limited al¬ 
most exclusively to hard seeds. This 
might seem to indicate that the birds 
feed to some extent upon grain, but 
the stomachs examined show only one 
kind, oats, and but little of that. The 
great bulk of the food is made up of 
grass and weed seeds, which form al¬ 
most the entire diet during winter, and 
the amount consumed is immense. 
In the agricultural region of the 
upper Mississippi Valley, by roadsides, 
on borders of cultivated fields, or in 
abandoned fields, wherever they can ob¬ 
tain a foothold, masses of rank weeds 
spring up and often form almost im¬ 
penetrable thickets which afford food 
and shelter for immense numbers of 
birds and enable them to withstand great cold and the most terrible blizzards. A 
person visiting one of these weed patches on a sunny morning in January, when 
the thermometer is 20° or more below zero, will be struck with the life and 
animation of the busy little inhabitants. Instead of sitting forlorn and half 
frozen, they may be seen flitting from branch to branch, twittering and 
fluttering, and showing every evidence of enjoyment and perfect comfort. If 
one of them is captured it will be found in excellent condition; in fact, a 
veritable ball of fat. 
The snowbird 29 and tree sparrow 30 are perhaps the most numerous of all the 
sparrows. Examination of many stomachs shows that in winter the tree spar¬ 
row feeds entirely upon seeds of weeds. 
Probably each bird consumes about 
one-fourth of an ounce a day. In an 
article contributed in 1881 to the New 
York Tribune the writer estimated the 
amount of weed seed annually de¬ 
stroyed by these birds in Iowa. On 
the basis of one-fourth of an ounce 
of seed eaten daily by each bird, and 
an average of 10 birds to each square 
mile, remaining in their winter range 
200 days, there would be a total of 
1,750,000 pounds, or S75 tons of weed 
seed consumed in a single season by 
this one species. Large as are these 
figures, they unquestionably fall far 
short of the reality. The estimate of 
10 birds to a square mile is very con¬ 
servative, for in Massachusetts, where 
the food supply is less than in the 
Western States, the tree sparrow is 
even more abundant than this in win¬ 
ter. The writer has known places in 
Iowa where several thousand tree spar¬ 
rows could be seen within the space of a 
few acres. This estimate, moreover, is for a single species, while, as a matter of 
fact, there are at least half a dozen birds (not all sparrows) that habitually 
feed during winter on these seeds. Farther south the tree sparrow is replaced 
in winter by the white-throated sparrow, 31 the white-crowned sparrow, 32 the fox 
Fig. 10.—Field sparrow. Length, about 
5S inches. 
Fig. 9.—Song sparrow. Length, about 
inches. 
20 Junco hyemalis. 
30 Spizella arborea. 
31 Zonotrichia albicollis. 
32 Zonotrichia leucoplirys. 
