ECONOMIC RELATIONS OF OUR BIRDS. 
449 
single locality in Europe, during one season, 300,000 sheep, and which has ruined 
large herds of cattle, and which, under favorable circumstances, has even 
attacked man, is due to a parasite, Faciola hepatica. This parasite is believed by 
those who have studied its habits, to pass through one stage of its transforma- 
tions in the bodies of fresh-water mollusks. If these mollusks are a necessary 
habitat of the fluke-rot parasite, whatever destroys them lessens the liabilities 
of its attacks. Quite a large number of birds and fishes and some insects feed 
upon fresh-water mollusks, but whether in so doing they are benefiting us, we 
cannot at present say. 
(7) A bird may render service by feeding upon noxious crustaceans and 
worms. Crawfish liave been so little studied in regard to their habits that an 
economic position cannot be satisfactorily assigned them at present. Prof.W. 
F . Bundy writes me in regard to their habits as follows; 
“ Crawfish feed on worms, small mollusks, insects that fall in their way, small 
fish, and in general any kind of animal food, especially carrion. They are in¬ 
dustrious scavengers. This latter item, with the additional ones that they form 
a not inconsiderable part of food for fish, and their damage to meadows by bur¬ 
rowing, indicate where they come in the most direct relation to human 
interests.” 
The river species he regards as beneficial. Those which burrow in meadows, 
building mud chimneys which become sun-baked and interfere quite seriously 
with mowing, he is in doubt in regard to, but inclines to the opinion that their 
services as scavengers moi*e than offset the damage they do. 
Crawfish are preyed upon to a considerable extent by various species of Herons 
and some other birds. The_Cowbird is said to eat the intestinal worms voided by 
cattle and hoi’ses. 
(8) Birds are serviceable wlien.they feed on carrion. Ordinarily, in a country and 
climate like that of Wisconsin, there appears to be but little need for large car¬ 
rion-eating animals. Birds of this class, therefore, which have other and very 
injurious tendencies, can hardly be tolerated in abundance merely for the pur¬ 
pose of consuming carrion. 
The injurious relations of birds may likewise be stated in the following prop¬ 
ositions: 
(1) A bird is harmful to us when it is injurious or destructive to useful plants. 
This may occur when the bird feeds upon the inner bark, buds, foliage, blossoms, 
fruit, or seeds of useful plants. 
It is in the destruction of cereals, either shortly after they are planted or when 
they are ripening, that our birds ai’e chiefly injurious in this direction at present, 
but even here their injuries have rarely assumed alarming proportions. Quite 
a large number of birds feed upon small fruits, but those which do are in other 
respects almost exclusively insectivorous. Even the Cherry Bird and Baltimore 
Oriole, which horticulturists tell us should be exterminated in mid-cheny time, 
feed quite as much upon insects as upon fruits. The Yellow-bellied Woodpecker 
is said to feed upon the inner bark of orchard and ornamental trees. Tlie Pur¬ 
ple Finch and some other birds occasionally eat the buds of fruit trees; their 
injury, however, has thus far been trifling. In the forests, during the winter, 
buds form a large part of the food of quite a number of birds. From the 
stomach of a Partridge were taken, in October, 302 white birch buds. While 
the number of buds which this species consumes during the winter is doubt¬ 
less very great, it is probable that its flesh will always amply compensate for 
the injury it does in this direction, to say notlnng of the insects which it con¬ 
sumes during the summer. 
VoL. 1 — 29 
