BIRDS AND INSECTS 
99 
The nature of a bird’s food can be determined by observing what it 
eats and by an examination of what it has eaten. It is, of course, often 
impossible to see just what a bird is eating or, even having seen, one 
still may not recognize the particular kind of insect, fruit or seed which 
has been swallowed. Expert analysis of the contents of the digestive 
tract is therefore essential to an accurate knowledge of the character 
of a bird’s food. The conclusions drawn from laboratory work should, 
however, be checked by studies in nature, to which the field ornithol- 
ogist may make valuable contributions. 
Looking from my window as I write, I see five Starlings ( Sturnus ) 
running actively about the lawn beneath a cherry tree, picking up 
fallen fruit. An examination of the contents of their stomachs would 
unquestionably reveal the presence of cherries, but I see this ground- 
feeder gather fallen cherries far more frequently than growing ones, 
and stomach analysis alone might, therefore, in a case of this kind, 
lead to a false estimate of a bird’s destructiveness. (On the study of 
food habits in the field, see especially Forbush’s “Useful Birds.”) 
Equally true is it that verdicts based only on casual observations 
of the bird in nature are far from the truth; and it is this kind of hasty 
conclusion that the economic ornithologist finds the greatest difficulty 
in combating. A Cooper’s Hawk may be seen to catch a chicken or 
scatter a flock of Bob-whites; Robins may be noted in the cherry trees 
or Catbirds in the strawberry bed, and without further evidence 
all Hawks are declared to be destroyers of poultry and game, and 
small birds generally devourers of fruit. But thanks to the investi- 
gations made by federal and state governments, as already mentioned, 
we are now in possession of accurate, incontrovertible data, and there is 
no excuse for signing a bird’s death warrant on false or insufficient 
observation. It has thus been determined that birds are of inestimable 
value to man (1) by eating harmful insects, their eggs and larvae; 
(2) by destroying the seeds of noxious weeds; (3) by devouring field 
mice and other small mammals which injure crops; and (4) by acting 
as scavengers. 
Birds and Insects.— Dr. L. C. Marlatt, of the United States De- 
partment of Agriculture, estimates that in the year 1904 the loss to 
our agricultural interests occasioned by insects amounted to $795,000,- 
000 (Yearbook, U. S. Dept. Agr., 1904, p. 464). Dr. A. D. Hopkins, 
also of the Department of Agriculture, estimates that insects cause an 
annual loss to our forestry and timber interests of $100,000,000. It 
is difficult for us to comprehend fully the significance of these figures, 
but at least they may serve to impress us with the value of any form of 
life which in turn preys upon insects, and in the front rank of insect 
enemies stand the birds. 
It is possible here only to give references (see beyond) to the now 
extensive literature containing exact statistics of this battle of the birds 
and the bugs. In these papers, for example, it will be found stated that 
the stomach of a single Cedar Waxwing contained 100 canker worms, 
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