100 BIRDS AND WEEDS 
that one Cuckoo had eaten 250 caterpillars, that 454 plant-lice were 
found in the stomach of one Chickadee, that a Nighthawk had made a 
meal on 60 grasshoppers, that a Flicker had devoured 1,000 chinch 
bugs, that a Scarlet Tanager was seen to eat 630 gypsy moth cater- 
pillars in eighteen minutes, or at the rate of 2,100 an hour; while a 
Maryland Yellow-throat ate 3,500 plant-lice in forty minutes, or at 
the rate of 5,270 an hour! 
As the destroyers of insects that breed disease, birds stand in an 
even closer economic relation to man. Five hundred mosquitos, for 
example, were found in the stomach of a single Nighthawk; Swallows 
and other wing-feeding birds also feed upon this pest, which, in the 
larval form, is eaten by various marsh-inhabiting birds. It is probable, 
therefore, that as our knowledge of the history of various diseases to 
which man is subject through insect attack increases, birds will here 
be found to be correspondingly valuable. 
In spite of the immense amount of authoritative data, of which we 
are now in possession, we are far from beginning to realize the profoundly 
important part played by insectivorous birds in holding in check the 
insects injurious to vegetation and to man. We may, however, accept 
without question the opinion of Henry W. Henshaw, Chief of the Biolog- 
ical Survey, who states as his conviction that without the services of 
insect-eating birds ‘it is more than likely—nay, it is almost certain— 
that within a limited time not only would successful agriculture be- 
come impossible, but the destruction of the greater part of vegetation 
would follow.” (Nat. Geog. Mag., 1908, p. 89.) 
Birds and Weeds.—It is not, however, only as a scourge to insects 
that the bird is of value to the farmer, but also as a destroyer of the 
seeds of weeds it performs a service of incalculable importance. Again 
we must turn to the researches of the economic ornithologist for those 
definite data (see especially papers by Judd) without which satisfactory 
conclusions cannot be reached. In passing we may merely state that 
700 seeds of the pigeon grass were taken from the stomach of a Tree 
Sparrow by Professor Beal, who estimates that this species destroys 
no less than 875 tons of weed-seed annually in the single state of Iowa; 
that 1,000 pigweed seeds were found in the stomach of a Snow Bunt- 
ing; that a Bob-white contained 5,000 seeds of pigeon grass, while a 
Mourning Dove had eaten the enormous number of 7,500 seeds of the 
yellow wood sorrel. 
Birds and Rodents —Still we have not given the birds all the credit 
due them as powerful allies of the agriculturist. Every farmer knows 
all too well how seriously small rodents, particularly field mice, can 
damage his crops in the field as well as in the storehouse or granary; 
but few farmers know that Hawks and Owls, birds they have aways 
believed should be killed on sight, are among nature’s most potent 
checks on the undue increase of these destructive little creatures. 
The loss which may follow ignorance of the economic value of 
Hawks and Owls has never been more clearly shown than by Dr. 
