The Food of Birds. 
95 
And here opportunity is afforded for careful and trust- 
worthy estimates of the ratios each element bears to the 
other, so that the average significance of the food can be 
discovered. Practically, this is indispensable. Whatever 
method fails of this, while its results may be interesting, 
and may have a certain general value, can never afford 
a basis for anything better than indefinite opinion. It 
can never settle the case for or against the birds. 
This method, while by far the best of the threei has its 
slight disadvantages. Some things eaten by birds leave 
no appreciable trace in- the stomach. For example, it is 
difficult, by this method, to determine with certainty those 
birds which greatly injure grapes by breaking the skin of 
the fruit and sipping the juice. This difficulty applies 
only to liquid food. Other errors may arise from the 
shorter or longer periods for which different kinds of 
food will last in the stomach; but of this we have no 
proof. I have depended almost wholly on this third 
method of investigation, because it is evidently the most 
profitable and reliable, and because the method of cur- 
sory observation having been resorted to heretofore, 
most of the recorded facts are due to it. So far as one 
method could correct the deficiencies of the other, it was 
desirable that this more tedious and laborious but more 
fruitful one should be given greater prominence. ^onc 
The stomachs of birds shot at all times of the year/and 
in all parts of the State, have been preserved in alcohol, 
each labeled with name, date and localilty. The contents 
of these stomachs were afterwards transferred, for per- 
manent preservation, to separate vials, bearing copies of 
the original labels. They were then examined, bit by bit, 
with the microscope, with whatever powers were neces- 
sary to the fullest possible understanding of each frag- 
ment. It has been no uncommon thing to spend half a 
day over a single bird. Full notes of the materials found 
in each stomach were made on separate slips, and after 
this careful examination an estimate was made and re- 
corded of the ratios of the different elements to the whole 
mass of the food of each individual. Objects which I was. 
not able to identify have usually been sent to some more 
