The Tree Sparrow 
63 
heat, he will be lost in wonder at the fact that these minute creatures not 
only stay alive but apparently keep comfortable and do not suffer in 
any way. 
With the object of getting some reliable facts as to the food of this 
sparrow in winter I once killed several and examined the contents of their 
stomachs. In the first lot taken the entire food consisted of weed-seeds, 
ragweed ( Ambrosia ) and foxtail (Chcetochloa) . A short time later 
another collection gave the same result; still later 
a third lot was taken, and still their stomachs con- A Diet of 
tained nothing but weed-seed, and it was soon evi- 
dent that to continue killing them would be a wanton waste of life, as 
the food in the stomachs was substantially the same in all. 
Probably the bird itself eats insects, as well as feeds them to its young, 
during the nesting-season ; but no stomachs have been taken at that time, 
and, as the bird breeds mostly, if not entirely, north of the United States, 
we have no notes of its food at that season. 
Where a bird subsists so extensively upon a single article of diet it is 
evident that it must make serious inroads upon the total amount of that 
particular food. In this case it is a drain from a definite, though unknown 
supply, not one that is constantly increasing as fast as drawn upon, like 
insects in summer. In order to gain some definite notion as to the actual 
amount of weed-seed eaten, notes were taken on the probable amount eaten 
every day by one bird, the number of birds of this species in the State, 
and the number of days of their stay. In this case the State of Iowa was 
the one under consideration. 
It is my opinion that Iowa contained areas of considerable size where 
the Tree Sparrows were distributed at the rate of 1,000 to the square mile, 
but probably not all of the State was populated at that rate. To be well 
within safe limits, an average of ten birds to the square mile was allowed. 
Observation indicated that each sparrow would eat not less than one- 
fourth of an ounce of seed daily, and that the birds 
spent an average of about 200 days in the State, A Total 
from their arrival in October till their departure for 
their northern home in April. Putting this data together, it appears 
that this one kind of bird must be credited with the yearly destruction, 
in Iowa alone, of 1,750,000 pounds, or 875 tons, of weed-seed. If this 
were loaded upon freight-cars at the ordinary load of 12 tons to a car 
it would make a train of 72 cars and leave a little over. 
These figures seem remarkable, but in my opinion they could be multi- 
plied by four with perfect safety. 
The Tree Sparrow, however, is not confined to the western interior 
for its winter home, but is found all along the northern United States 
from ocean to ocean. It is true that the eastern and more wooded States 
do not afford so rich a supply of food as do those of the Mississippi 
Valley, but weeds enough are left by farmers everywhere, together with 
those by roadsides and waste places, to supply a good many birds; and 
